Some of you who attended the Montauk Rendevous, that Wits End has a smoking problem. She is running 2 300HP 1989 Cummins 6BTAs with 1700 hours. I blamed most of the problems on fuel or air cleaners. At Montauk it was suggested by many particularly Capt Pat and Walter that I go with the S&N air filters, which I have done.
The smoking problem still occurs when under full load at 1900 RPM at the moment the turbo's kick in to 2000 RPM and then the she either gets over and takes off or spews fuel and black smoke out the exhaust, some would say looks like she is on fire. Even when she planes, the water out the exhaust is black with fuel, regardless of the RPM. But, performance is great 33-34 kts, WOT at 2900 and fuel consumption in 2-4 ft seas 15 gpr at a 26 kt cruise. However, problem gets very hairy in a following sea, as I actually without much power to plane the boat or get through.
Tom Ward and I accompanied each other to BI and Nantucket and witnessed the smoking issue. Tom turned me over to S&S Propellers, as I have been through examining the fuel system, air intake system and cooling system with no appreciable results. After discussing the matter with S&S Propellers, they recommended and sent 2 18X24 4 blade props with #1 cup. I had been running 20X27 S/N X 146 props which also always caused excessive vibration through the boat at idle speed (600RPM) and operating to about 7 kts at idle and more vibration at 2400 RPM to 2900 RPM or WOT which would shake the hatch covers. What was noticable with the old props was when the trans were engaged, the rpm would drop 200 RPM and almost shut down.
I put on the new 4 blades without a full load and the smoking and vibration ceased and the exhaust water was clean. However, the planning RPM point has increased to 2100 and WOT has increased to 3100 RPM. I realize fuel consumption will change as cruise at 26 kts is now 2400 RPM, instead of 2200 RPM. I am pleased with results so far, although tomorrow I will be testing under full load.
Yet there is a doubt in the back of my mind, because the discussions on this board always seem to indicate a 20 X 28 seems to work best on the 31 or bigger is better. Am I missing something? Will the contours of these S & S props cause problems given their size or in some way tire the 6BTAs before their time?
The irony in all of this for me is, the change of props solved the problem I was trying to solve--excessive smoking--I suspect I am now concerned I am creating another problem. Any discussion on this subject would be very helpful.
More On Props- FBC 6BTAs 300HP
Moderators: CaptPatrick, mike ohlstein, Bruce
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jeffery pagano
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oh my god! where did you get your information.there is no way in hell a cummins 6bta-m2 cpl 970 300hp would ever be proped correctly in a 31bertram with 1.5 gears.4 blade,full cup 20"x 23" is were you should safely be at.a little longer you would have scored #6 piston or worse
trust me 20x27 is insane for that engine a certain blow up.
trust me 20x27 is insane for that engine a certain blow up.
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jeffery pagano
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Bob, maybe you could translate your comments for me, being the relative novice as to the 31's, particulary as to choosing a correct prop, which is why I posted the question in the first place.
Are you saying that the original prop size 20 X 27 which have been on the boat since 1989, "...is insane for that engine a certain blow up"? All I can tell you is that Cummins propped the boat way back when it installed the engines in 1989 as a demo for the turbo'd 6BTA. So are you telling me it has been mispropped for the past 1700 hours and/or 18 years?
Or are you saying that the props which were recommended by S&S 18 X 24 4 blade # 1 cup props are wrong and that size is "..a certain blow up"? Are you saying remove these props immediately and not further test with a full load tomorrow?
Or are you saying the only "safe" prop is the 20 X 23, and both the original 20 X 27 props and the recommended 18 X 24 props both are "..a certain blow up"?
Give me a break will you. The info I got was from this board, S&S, Cummins and the prior owner and my experience with the 31 over the past 4 years.
Yes, the gearing is 1.5.
Are you saying that the original prop size 20 X 27 which have been on the boat since 1989, "...is insane for that engine a certain blow up"? All I can tell you is that Cummins propped the boat way back when it installed the engines in 1989 as a demo for the turbo'd 6BTA. So are you telling me it has been mispropped for the past 1700 hours and/or 18 years?
Or are you saying that the props which were recommended by S&S 18 X 24 4 blade # 1 cup props are wrong and that size is "..a certain blow up"? Are you saying remove these props immediately and not further test with a full load tomorrow?
Or are you saying the only "safe" prop is the 20 X 23, and both the original 20 X 27 props and the recommended 18 X 24 props both are "..a certain blow up"?
Give me a break will you. The info I got was from this board, S&S, Cummins and the prior owner and my experience with the 31 over the past 4 years.
Yes, the gearing is 1.5.
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Capt. Mike Holmes
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Props
I think Bob was saying 27 - 28 inches is a lot of pitch, and I fully agree - although I don't have his knowledge and experience. In the old days, "squared" props were considered the optimum - such as a 20 x 20. I understand now that on the newer, higher hp and rpm engines, it is recommended to go above diameter on the pitch, as yours has been done - but this does seem an extreme case. I run 22 x 24 three blade nibrals behind 2:1 gears on my Cummins, which are probably around 250 - 260 hp, but a lot of 31's don't have room for a 22" diameter prop. My prop guy thought 24" of pitch on these props (Nibral) was about s much as he would go. The 4 blades you have tried seem a better match than what you were running, as possibly proven by the fact that it stopped smoking and vibrating. Too much prop loading for the gear and hp can cause excessive heat on the cylinder exhaust, as Bob pointed out, which can be deadly for the engine.
"There is nothing quite so satisfying, as simply messing around in boats."
Easy Guys.
IIRC, Bob was the only one on the board who mentioned using something in the area of a 27" pitched prop on a 31.
Due to the severity of that pitch, in gear launching and heavy rpm loss can occur.
By Jeff's post it seems that it was over propped from the begininng by his description of what was going on. Just because it was originaly done that way by a manufacturer does not mean it was done correctly.
Now it seems Jeff is performing correctly.
A 19x24 or 20x23 prop with a medium cup seems to work the best on a 31 as Pat and I have always said.
But this brings up high HP/low rpm engines in the 31 and being able to turn a propeller to load the engines without going to prop pockets or high pitched props.
Neither of which is practical in the 31 application.
Jeff it looks like your okay at this point. 3000 revs is okay as long as you are not hitting the governor. Certainly a K&N air intake is better than stock and wasn't a waste of money.
If you are so inclined, I would get a mechanic to pull a compression check to varify that no cylinder scoring had taken place. Well worth a couple of hours labor.
IIRC, Bob was the only one on the board who mentioned using something in the area of a 27" pitched prop on a 31.
Due to the severity of that pitch, in gear launching and heavy rpm loss can occur.
By Jeff's post it seems that it was over propped from the begininng by his description of what was going on. Just because it was originaly done that way by a manufacturer does not mean it was done correctly.
Now it seems Jeff is performing correctly.
A 19x24 or 20x23 prop with a medium cup seems to work the best on a 31 as Pat and I have always said.
But this brings up high HP/low rpm engines in the 31 and being able to turn a propeller to load the engines without going to prop pockets or high pitched props.
Neither of which is practical in the 31 application.
Jeff it looks like your okay at this point. 3000 revs is okay as long as you are not hitting the governor. Certainly a K&N air intake is better than stock and wasn't a waste of money.
If you are so inclined, I would get a mechanic to pull a compression check to varify that no cylinder scoring had taken place. Well worth a couple of hours labor.
Last edited by Bruce on Aug 19th, '07, 10:47, edited 1 time in total.
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jeffery pagano
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Everyone thanks for your input. This afternoon I will sea trial the 18 X 24 props with a full load. Given that I have been apparently overpropped all these years, it goes to show me what little the engine manufacturers actually know about the applications and in the process create the engine problems we have to continually pay for and manage. It also demonstrates the value of this site, blending experience, know how and vision as applied to the 31.
Now the true test is my dog, who hates the vibration from what we thought was a consequence of the Cummins engines over the past few years and stands for hours in the cockpit with her tail between her legs, while we are fishing, as opposed to falling asleep on the engine covers as she did when we owned Yanmars in a different 31. I hope she now relaxes due to the elimination of smoke and vibration.
Any more comments would still be appreciated.
Now the true test is my dog, who hates the vibration from what we thought was a consequence of the Cummins engines over the past few years and stands for hours in the cockpit with her tail between her legs, while we are fishing, as opposed to falling asleep on the engine covers as she did when we owned Yanmars in a different 31. I hope she now relaxes due to the elimination of smoke and vibration.
Any more comments would still be appreciated.
thank you bruce ,my use of 27"pitch is a whole differant ballgame,the only similarity between my 330 and your 300-m2 is the harmanic balancer completly differant engine not even the same block.
now back to jeff want i am saying is a 20"x 27" pitch is running the snot out of that engine----- way overproped yes the factory was trying to impress somebody in it`s day but they found out the hard way you can`t do this with a cpl970 especially 1989 vintage. in every other case you can go by the golden rule "must rev up to governer set point with fully loaded boat"that motor has a few design faults and went thru 9 major upgrades by 1992.bruce is even more conservative than me and rightfully so 20x 23 is safe or s&s with 18x24.i think i would like a little more diameter than 18 however.if you have 1700hours on those 27 pitch props in a loaded condition they is a strong possibility of a small crack on #6 port of the exhaust manifold.it will be on the top right side as you look at it.machinest dykem will make the crack stand out.quite possibly cummins replaces the exhaust manifold back in 1990 while under warranty.here are the numbers if upgraded; cylinder head-3926205,exhaust manifold-3922122,turbo-3921926,aftercooler3928503.
now back to jeff want i am saying is a 20"x 27" pitch is running the snot out of that engine----- way overproped yes the factory was trying to impress somebody in it`s day but they found out the hard way you can`t do this with a cpl970 especially 1989 vintage. in every other case you can go by the golden rule "must rev up to governer set point with fully loaded boat"that motor has a few design faults and went thru 9 major upgrades by 1992.bruce is even more conservative than me and rightfully so 20x 23 is safe or s&s with 18x24.i think i would like a little more diameter than 18 however.if you have 1700hours on those 27 pitch props in a loaded condition they is a strong possibility of a small crack on #6 port of the exhaust manifold.it will be on the top right side as you look at it.machinest dykem will make the crack stand out.quite possibly cummins replaces the exhaust manifold back in 1990 while under warranty.here are the numbers if upgraded; cylinder head-3926205,exhaust manifold-3922122,turbo-3921926,aftercooler3928503.
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In Memory of Vicroy
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The consensus (per Tony Athens) is to prop the CPL 970s to 3000+ and run them like they are 250s, i.e. cruise at no more than 2400. The 6BTA 250s in my FBC turn 21x22 three blades thru 1.5 gears and is a little under propped.....top end about 27 kts, 24 at 2400 cruise. But she will carry any load you pile on her at the same speed. Like 13 guys & all their gear, full fuel and a load of ice - 24.5 kts at 2400, my "happy cruise". AJ will go from idle to WOT in about 7-8 seconds, leaves a good puff of black smoke, then clears right up. 16 GPH with the genset running. About 2500 trouble free hours once I got the damn Sherwood pumps and impellers sorted out courtesy of Tony Athens' aftermarket impellers and pump parts. I'm three years into his impellers and they still 'impel' water just fine vs. the 6 months on the stock Sherwood garbage.
I installed the S&B filters several years ago and noticed a positive difference, plus they don't waterlog like the paper ones do. I bought them from Tony and they were about $75 ea. as I recall and he says the dirtier they get, the better they work, only need to clean them about every 1,000 hours unless you suck something like motor box insulation.
into them.
Went to crank AJ yesterday and when I took the Stamoid cover off the instrument panel the doggone dirt daubers had built another nest around the Sea Star helm pump.....chipped off most of it. I put some mothballs under the cover this time....you guys got any better ideas to repel dirt daubers? Need the cover to keep the sun from eating up the Cummins plastic panels......
UV
I installed the S&B filters several years ago and noticed a positive difference, plus they don't waterlog like the paper ones do. I bought them from Tony and they were about $75 ea. as I recall and he says the dirtier they get, the better they work, only need to clean them about every 1,000 hours unless you suck something like motor box insulation.
into them.
Went to crank AJ yesterday and when I took the Stamoid cover off the instrument panel the doggone dirt daubers had built another nest around the Sea Star helm pump.....chipped off most of it. I put some mothballs under the cover this time....you guys got any better ideas to repel dirt daubers? Need the cover to keep the sun from eating up the Cummins plastic panels......
UV
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jeffery pagano
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Well, my dog approved the new props during the sea trial, she even laid down in the cockpit, while underway at 15 kts.
With a full load, 220 gallons 3 people and fishing gear for 5, the performance was not as fast as before but very strong, particularly at take off--up and over without any smoke whatsoever. Before with the 20X27 3 blade props, she would cruise at 26kts at 2200RPM, 28 at 2600 and 33 at 2900-WOT. As to speed, she is now probably a bit underpropped, but speed is now almost the same as RPM--23 at 2200RPM, 25 at 2450 RPM, 27 at 2600 RPM and 31.5 at 3000 RPM-WOT. For the first time my transom is clean after 5 hours of hard running. The temperature dropped 7 degrees in the port engine and 5 in the other from operating with the old props.
I checked the exhaust and found no cracks in either manifold, as I replaced both heads 160 hours ago, replacing the original injectors. Perhaps, I caught the situation just in time. Basically with the 18 X 24 4 blades with a #1 cup, the 31 ran stronger than ever throughout the power curve, without any vibration and the total elimination of soot and smoke. The exhaust water was clear within an hour of the run, whereas with the 20 X 27 props the exhaust water was always black.
I don't know whether it is wise to settle with these props, but given the abuse the system went through with the 20X27 props for the past 17 years, I feel it best to keep these 4 blades, as a sort of an "assisted living" arrangement for my 1700 hour Cummins engines.
With a full load, 220 gallons 3 people and fishing gear for 5, the performance was not as fast as before but very strong, particularly at take off--up and over without any smoke whatsoever. Before with the 20X27 3 blade props, she would cruise at 26kts at 2200RPM, 28 at 2600 and 33 at 2900-WOT. As to speed, she is now probably a bit underpropped, but speed is now almost the same as RPM--23 at 2200RPM, 25 at 2450 RPM, 27 at 2600 RPM and 31.5 at 3000 RPM-WOT. For the first time my transom is clean after 5 hours of hard running. The temperature dropped 7 degrees in the port engine and 5 in the other from operating with the old props.
I checked the exhaust and found no cracks in either manifold, as I replaced both heads 160 hours ago, replacing the original injectors. Perhaps, I caught the situation just in time. Basically with the 18 X 24 4 blades with a #1 cup, the 31 ran stronger than ever throughout the power curve, without any vibration and the total elimination of soot and smoke. The exhaust water was clear within an hour of the run, whereas with the 20 X 27 props the exhaust water was always black.
I don't know whether it is wise to settle with these props, but given the abuse the system went through with the 20X27 props for the past 17 years, I feel it best to keep these 4 blades, as a sort of an "assisted living" arrangement for my 1700 hour Cummins engines.
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In Memory Walter K
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Given the years of service with the original props, I would never have thought the solution to your problems would be overpropping. Proves the addage "you're never to old to learn something new". The site saves the day again! The mystery to me is why it manifested itself in smoke, dirty water and vibrations only recently. I'll bet the boat will troll and dock a lot better with the new props. Congratulations and I hope you like the new air filters. Walter
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jeffery pagano
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- Location: East Hampton, NY
Everyone, there is nothing better than a solution that actually works beyond expectations and a happy dog.
The thanks runs to all of you who entered into the discussion, especially Bob who pissed me off in a way that made me think twice about the S&S solution and those of you who calmly indicated I was nuts to even consider the original set up by Cummins, as appropriate or even a logical reference point. Of course Bob had to scare me again by forcing me to closely examine the new heads. Indeed the 20X27 props were probably why I needed to replace the heads 140 hours ago. Duh.......
But importantly, Walter and Capt Pat at the Montauk R. started the process of focusing on the problem, instead of accepting it, through the air filter solution, which did not work, but nevertheless improved the situation. Now with the new props this solution enhances performance.
And most importantly, Tom and Larry Ward who unfortunately followed Wits End to Nantucket from BI for a time (until we allowed the 38 to overtake us in the fog) and when we arrived showed me pictures they took underway in a following sea. Yes, the pictures told the story in a little white but much black. From behind we looked as if we were on fire--smoke-smoke-smoke. And on a rainy day the three of us focused on the problem, went through the solutions already effectuated, went through them, and then put me in contact with S&S Propeller, at Tom's insistence-he even dialed the number and put the phone to my ear. Like Walter, I would have never imagined props would have solved so many issues. In retrospect, it now seems obvious, what more fundamental element to assure overall performance.
All day long today, I kept saying to my youngest son: " I can't believe the smoke and vibrations are gone". Everyone is pleased, especially our dog, Blue.
Thanks...... I am no longer at my "Wits End". Perhaps I should rename the 31, bad solution. On to the next issue.....
The thanks runs to all of you who entered into the discussion, especially Bob who pissed me off in a way that made me think twice about the S&S solution and those of you who calmly indicated I was nuts to even consider the original set up by Cummins, as appropriate or even a logical reference point. Of course Bob had to scare me again by forcing me to closely examine the new heads. Indeed the 20X27 props were probably why I needed to replace the heads 140 hours ago. Duh.......
But importantly, Walter and Capt Pat at the Montauk R. started the process of focusing on the problem, instead of accepting it, through the air filter solution, which did not work, but nevertheless improved the situation. Now with the new props this solution enhances performance.
And most importantly, Tom and Larry Ward who unfortunately followed Wits End to Nantucket from BI for a time (until we allowed the 38 to overtake us in the fog) and when we arrived showed me pictures they took underway in a following sea. Yes, the pictures told the story in a little white but much black. From behind we looked as if we were on fire--smoke-smoke-smoke. And on a rainy day the three of us focused on the problem, went through the solutions already effectuated, went through them, and then put me in contact with S&S Propeller, at Tom's insistence-he even dialed the number and put the phone to my ear. Like Walter, I would have never imagined props would have solved so many issues. In retrospect, it now seems obvious, what more fundamental element to assure overall performance.
All day long today, I kept saying to my youngest son: " I can't believe the smoke and vibrations are gone". Everyone is pleased, especially our dog, Blue.
Thanks...... I am no longer at my "Wits End". Perhaps I should rename the 31, bad solution. On to the next issue.....
jeff sorry if i offended you.i just wanted to stop you in your tracks instead off beating around the bush.the reason the new heads held off the onslaugh of excess heat was the exhaust valve rotators.pretty much bulletproof also cummins went to the a smaller injector which allow more
"meat" in the combustion chamber to dessipate heat.the reduction of operating temperture is due to a dramatic drop in egt.those engines will live a long time with your setup.if you ever need help i am just a pm. away. and a 1 hour ride----------------bob
"meat" in the combustion chamber to dessipate heat.the reduction of operating temperture is due to a dramatic drop in egt.those engines will live a long time with your setup.if you ever need help i am just a pm. away. and a 1 hour ride----------------bob
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jeffery pagano
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jeff over at oakdale yacth we have a giant forklift that can lift a 40' boat.the lift can use the forks as a "clamshell" just back the boat into the workslip the forks open up and scoop the 31bert out of the water.it takes me about 12minutes to change props on my 31 and back in the water.around febuary when all is quiet we have a prop room with 500 props.i tryed 5blade,4blade and 3blade and i even eye up a pair of 6blade.
the only possitive conclusion i can say is you can drive a bertram 31 all day at 40 all you need is a12 to 15 degree positive rake on the props and the bert will maintain a perfect bow proud profile.off course i have no idea how you back into a slip at 12knots but i am giving it some through.i have vulcan torsional drive system on my engines which consist of a 2 step flywheel,removal of the housing and replaced with a steel one and of course the bulletproof damper.no springs or slip,like a raceboat with crash boxes man it`s in or out 0 hesitation.the good news is you can slap from foward to reverse like docking or backing down on a fish the bad news is if anybody is on the gunnels trying to secure a line ---they are in the drink!!! good for 550 hp sold by zf .
the only possitive conclusion i can say is you can drive a bertram 31 all day at 40 all you need is a12 to 15 degree positive rake on the props and the bert will maintain a perfect bow proud profile.off course i have no idea how you back into a slip at 12knots but i am giving it some through.i have vulcan torsional drive system on my engines which consist of a 2 step flywheel,removal of the housing and replaced with a steel one and of course the bulletproof damper.no springs or slip,like a raceboat with crash boxes man it`s in or out 0 hesitation.the good news is you can slap from foward to reverse like docking or backing down on a fish the bad news is if anybody is on the gunnels trying to secure a line ---they are in the drink!!! good for 550 hp sold by zf .
Be carefull about making absolutes.you can drive a bertram 31 all day at 40 all you need is a12 to 15 degree positive rake on the props and the bert will maintain a perfect bow proud profile
Forward weight problems will nose over a 31 to the point where the forward V acts like a rudder keeping the boat from responding to its helm.
Following seas make the problem happen at lower speeds.
Add to this propeller pitching that actually lifts the back of the boat adding to the problem.
The flatter the blade(higher pitch) makes the prop want to climb right out of the water.
Real world problems I have seen on two 31's.
Nothing is an absolute in the world of boating.
bruce this is what i posted a while back on the bertram climbing out of the water.when i had those radical props on the boat (21x27 radical cup and rake) the chase boat riding along side said at 38 i was starting to ride on the bottom two strakes and wanted to know if i was losing any steering,i made those huge rudders and don`t really know if this kept me going straight but i did not feel any chinewalking whatsoever,don`t forget this bert was weight on the travel lift about 9700lbs.the boat boat maintain a perfect plane beyond that can`t really say if it was pot luck or perfect balance ,all the weight is midship the cabin was damm near empty.what it comes down to is a 31 bert can be used after modification for a day boat or picnic boat capable of 40 if balance is observed.
Jeff,
Glad to see you got your problem worked out. It was great seeing you and the boys at Oak Bluffs. Do me a favor and shoot me an email with the picuture you took of the boat off of State Beach:
doug.leblanc@verizon.net
Glad to see you got your problem worked out. It was great seeing you and the boys at Oak Bluffs. Do me a favor and shoot me an email with the picuture you took of the boat off of State Beach:
doug.leblanc@verizon.net
Regards,
Doug L.
Doug L.
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Capt Dick Dean
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JohnCranston
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Capt. Mike Holmes
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To John
John, I hauled at Tempest today to install that transducer, asked Jim about putting enignes in for you - he said bring it on. Ran up the creek to look at my new lots, 2700 rpm on both engines, 25 knots.
"There is nothing quite so satisfying, as simply messing around in boats."
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JohnCranston
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Capt. Mike Holmes
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Call
If I don't answer at the house, try my cell (281/814-1464), got to splash the boat this morning.
"There is nothing quite so satisfying, as simply messing around in boats."
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