I’ve got a topic where I really need the help of Bertram31.com members. My partner and I are in contract on a 1987 Bertram 50 with DD 8v92TA (735 hp). We did the Sea Trial yesterday and she topped out (in two directions) at 2000rpm and 22.5 knots. My understanding was that these engines should spin up to 2300 or a bit over and top speed would be about 26-27 knots, with cruise being at 1850rpms and speed being 21-22 knots. We ran her up in neutral and she still topped out at 2000.
Here’s the background. Boat has not been run much at all in past year as previous owner passed away. Fuel is prob a year, or more, older. Boat has a dinghy on the forward deck and a hardtop on the flybridge, but not much else would be different from a standard Bertram 50. Offsetting the added weight, forward fuel tank holds approx 525 gallons and was on empty and aft tank is similar size and was between ¼ and ½ full. Water tanks were about ¾ full and we had about 7 people on board. Seas were pretty mild, maybe 1-2 feet. Boat hull had been cleaned 2 days earlier.
Engines fired up right away. When we took her up to speed, there was a bunch of dark smoke, but that died away pretty quickly. Mechanic was onboard and confirmed that the actual rpms being put out were within 25 of what was shown on the helm and said that at 2000 rpms (most we got)the throttles were all the way back and the engines were running well (not appearing to struggle).
At 2000 top, if we take off 20% for a cruising speed, I think we’d have been in the 16-17 knot range. So seems like about 5 knots off top and cruising speeds.
First thought was that if boat hull is clean and engines are running correctly, might be a prop issue. However, even if we have a larger prop, I would not think a smaller prop turning quicker would make that much difference in speed. Other idea was maybe it had to do with the quality of the fuel.
My partner and I really like the boat. Overall, she is in good shape, but this really raised a flag for us. Would love any insights or perspective on the following:
- Experiences on a similar boat – correct rpm ranges, speeds expected, etc.
- Ideas on what might be going on or an approach to figuring out the issue.
- Thoughts on whether this is to be expected on an older Bertram
- Any other ideas or commentary very welcome
I’m not a mechanic, and I’m really hoping members might be willing to give me some good guidance – any feedback at all is extremely appreciated.
Thanks so much,
John
Sea Trial and potential problems with a Bertram 50
Moderators: CaptPatrick, mike ohlstein, Bruce
If engines won't turn over 2000 without a load, they are not going to turn over 2000 when underway.
I'm not a menchanic by any stretch, but I'd check fuel filters, air filter then get into looking for anything that may be preventing the throttle from opening further and check to see if governer is set correctly.
I'm not a menchanic by any stretch, but I'd check fuel filters, air filter then get into looking for anything that may be preventing the throttle from opening further and check to see if governer is set correctly.
-
CaptPatrick
- Founder/Admin
- Posts: 4161
- Joined: Jun 7th, '06, 14:25
- Location: 834 Scott Dr., LLANO, TX 78643 - 325.248.0809 bertram31@bertram31.com
There is something holding you back within the engine or throttle cable setup. The two most obvious culprits are throttles not being pushed wide open, (as Carl stated), or the governer has been set for a lower RPM.We ran her up in neutral and she still topped out at 2000
In case it's the throttle/cable that's an issue, try running the engine up to full throttle on the controls & see if you can manually increase the RPMs directly on the engine. If you only get a small increase, disconnect the cable from the engine & bring the engine to WOT.
If that doesn't locate the problem, have a mechanic, (unless you feel comfortable doing it yourself), adjust the governer.
If the boat was in charter, it's common for either the owner or captain to set the governer at a lower RPM to purposely keep anyone from running at max RPM...
Those are the two easy to checks. If neither solve the problem, get back to us...
Br,
Patrick
-
scot
- Senior Member
- Posts: 1470
- Joined: Oct 3rd, '06, 09:47
- Location: Hurricane Alley, Texas
- Contact:
Everything stated is true. The engines should reach 2300-2350 WOT...load or no load.
I'm a Detroit fan and the 8V92TA is a bunch of engine. With that stated, you did not say how many hours are on the engines? Hours will have a bigger impact on those engines than lower hp Detroits. They are set up at 1hp per 1 cu in. That is making a lot of horsepower for any diesel to live a super long life. Based on my research those engines "may" only go somewhere between 2000-2500 hour between MOH's. They are wet liner engines and can often be re-built in the boat, assuming no major damage.
My point is NOT to slame those engines! I like 8V92's, just don't think they would go 8000-10,000 hours between rebuilds when set up at those hp ratings. When they are "souped up" they don't go forever. The cooling system needs to be in top notch shape.
Don't fret the black smoke at fire up, pretty normal...but it should clear up once the engines are warm, as you stated it did.
Good luck
I'm a Detroit fan and the 8V92TA is a bunch of engine. With that stated, you did not say how many hours are on the engines? Hours will have a bigger impact on those engines than lower hp Detroits. They are set up at 1hp per 1 cu in. That is making a lot of horsepower for any diesel to live a super long life. Based on my research those engines "may" only go somewhere between 2000-2500 hour between MOH's. They are wet liner engines and can often be re-built in the boat, assuming no major damage.
My point is NOT to slame those engines! I like 8V92's, just don't think they would go 8000-10,000 hours between rebuilds when set up at those hp ratings. When they are "souped up" they don't go forever. The cooling system needs to be in top notch shape.
Don't fret the black smoke at fire up, pretty normal...but it should clear up once the engines are warm, as you stated it did.
Good luck
Scot
1969 Bertram 25 "Roly Poly"
she'll float one of these days.. no really it will :-0
1969 Bertram 25 "Roly Poly"
she'll float one of these days.. no really it will :-0
Ditto on what Sim says.. change the fuel filters and either change or at least clean the air filters. Old fuel in a warm climate can grow lots of filter clogging algae, especially in partially filled tanks and a year or so with no circulation.. Surprised your engine tech did not say anything about them. If one engine was not able to keep up with the other I would worry about it having a problem, but when both engines run pretty much the same I would look for fuel issues, air issues, and governor issues first.
If they both can only reach 2,000 RPM under no-load condition it sounds as if is a governor setting issue.
If they both can only reach 2,000 RPM under no-load condition it sounds as if is a governor setting issue.
Frank B
1983 Bertram 33 FBC "Phoenix"
--------------
Trump lied! Washington DC isn't a swamp.. it is a cesspool!
1983 Bertram 33 FBC "Phoenix"
--------------
Trump lied! Washington DC isn't a swamp.. it is a cesspool!
Pat may be correct that the throttle stop was reset.
That is way too much HP for that block and the high cylinder temps will quickly wipe the oil film leading to piston and liner scuffing. Resetting the throttle stop was a common place for the owner after the first 1200/per hole rebuild.
The other thing if its fuel would be to have the mechanic install a vacuum guage right at the engine fuel inlets and watch while throttling up.
If its fuel then its a easy fix. If the stops have been reset to save the motors then if you can live with that, fine. If you can't and want to up to rated, then can you live with the expense of repairs?
That is way too much HP for that block and the high cylinder temps will quickly wipe the oil film leading to piston and liner scuffing. Resetting the throttle stop was a common place for the owner after the first 1200/per hole rebuild.
The other thing if its fuel would be to have the mechanic install a vacuum guage right at the engine fuel inlets and watch while throttling up.
No offense but it didn't. Don't fool yourself into thinking that. When your underturning rated rpm on a diesel, especially Detroit by 350 rpm, thats a major problem.The boat ran well overall
If its fuel then its a easy fix. If the stops have been reset to save the motors then if you can live with that, fine. If you can't and want to up to rated, then can you live with the expense of repairs?
That does make a difference.
Cause if its props, those motors have been over stressed.
Now has anyone pulled the block inspection covers and checked the liners?
Other than the black smoke, any white? Not water vapor but white?
Make sure nothing other than 30 micron are used in the primary filters.
The installation of the vacuum guage will confirm a blockage pretty quick.
Fuel smell can determine if its varnish'd.
But in the end, those motors are at the end of their major time and will be looking for another very soon. Keep that in mind.
And for damn sure get a real good Detroit guy to do a complete survey.
Cause if its props, those motors have been over stressed.
Now has anyone pulled the block inspection covers and checked the liners?
Other than the black smoke, any white? Not water vapor but white?
Make sure nothing other than 30 micron are used in the primary filters.
The installation of the vacuum guage will confirm a blockage pretty quick.
Fuel smell can determine if its varnish'd.
But in the end, those motors are at the end of their major time and will be looking for another very soon. Keep that in mind.
And for damn sure get a real good Detroit guy to do a complete survey.
OK I'll play
I'd plan on bidding the boat based on the fact that the engines are at best a major overhaul. Most of the components on the late 80's engines have been through some type of a redesign and not available.
The engines are not efficient by todays standards and because they are 2 cycle don't make horsepower and torque until very late in the rpm band. So lets say you had 8V92's at 735hp, the number is based on 2350 rpm. You cruise all day at 1900 rpm your using only 550hp of the 735.
Yank em they have value on the used market. Take advantage of that before they become boat anchors. Get a set of QSM11 Cummins remans and drop them in 700hp in recreational form. 4 cycle which means they build peak torque early in the band. Cruise them at 80% and your at 560hp the same as your 92's except for the fact that you'll be using roughly 25% less fuel.
I'd plan on bidding the boat based on the fact that the engines are at best a major overhaul. Most of the components on the late 80's engines have been through some type of a redesign and not available.
The engines are not efficient by todays standards and because they are 2 cycle don't make horsepower and torque until very late in the rpm band. So lets say you had 8V92's at 735hp, the number is based on 2350 rpm. You cruise all day at 1900 rpm your using only 550hp of the 735.
Yank em they have value on the used market. Take advantage of that before they become boat anchors. Get a set of QSM11 Cummins remans and drop them in 700hp in recreational form. 4 cycle which means they build peak torque early in the band. Cruise them at 80% and your at 560hp the same as your 92's except for the fact that you'll be using roughly 25% less fuel.
KR
JP
1977 RLDT "CHIMERA"
JP
1977 RLDT "CHIMERA"
-
scot
- Senior Member
- Posts: 1470
- Joined: Oct 3rd, '06, 09:47
- Location: Hurricane Alley, Texas
- Contact:
Actually JP it's just the opposite. The Detroit 2 stroke makes MORE torque at lower rpm's than a 4 cycle diesel, due to the stroke and firing cycles.
See Pascoe article: http://www.yachtsurvey.com/comparing_diesel_types.htm
Short version:
"Two cycle and four cycle engines each have their pros and cons. The operating system of the two cycle is radically different than the four cycle, which operates more like an ordinary gas engine without spark plugs. The Detroit Diesel engine is unique and is not offered by any other manufacturer. This engine utilizes a moderately heavy cylinder block that is quite complex in its casting. Compared to a MTU or Volvo, it is light; compared with Yanmar or Cummins, it is heavy. It is a long stroke, smaller bore engine than most four cycles. The Cat 3208, for example, has a fairly short stroke, as do the Cummins V-8’s. This gives the Detroit engine considerably higher torque at lower speed ranges, but limits its top RPM range: the longer the stroke, the slower the engine has to run. Thus, higher power at lower speeds.
Credit: Detroit Diesel Allison
The Detroit injector system is just one of the major differences over four cycle engines. The two stroke cycle.
The push rods of these engines are also about 33% longer than most 4 stroke engines, creating more rotational mass and therefore more rotational torque. Altogether, the engine delivers more power from less displacement, lower speed, but higher casting weights, while fuel consumptions remain approximately the same."
See Pascoe article: http://www.yachtsurvey.com/comparing_diesel_types.htm
Short version:
"Two cycle and four cycle engines each have their pros and cons. The operating system of the two cycle is radically different than the four cycle, which operates more like an ordinary gas engine without spark plugs. The Detroit Diesel engine is unique and is not offered by any other manufacturer. This engine utilizes a moderately heavy cylinder block that is quite complex in its casting. Compared to a MTU or Volvo, it is light; compared with Yanmar or Cummins, it is heavy. It is a long stroke, smaller bore engine than most four cycles. The Cat 3208, for example, has a fairly short stroke, as do the Cummins V-8’s. This gives the Detroit engine considerably higher torque at lower speed ranges, but limits its top RPM range: the longer the stroke, the slower the engine has to run. Thus, higher power at lower speeds.
Credit: Detroit Diesel Allison
The Detroit injector system is just one of the major differences over four cycle engines. The two stroke cycle.
The push rods of these engines are also about 33% longer than most 4 stroke engines, creating more rotational mass and therefore more rotational torque. Altogether, the engine delivers more power from less displacement, lower speed, but higher casting weights, while fuel consumptions remain approximately the same."
Scot
1969 Bertram 25 "Roly Poly"
she'll float one of these days.. no really it will :-0
1969 Bertram 25 "Roly Poly"
she'll float one of these days.. no really it will :-0
-
In Memory of Vicroy
- Senior Member
- Posts: 2340
- Joined: Jun 29th, '06, 09:19
- Location: Baton Rouge, LA
DD 92 TAs are only for the real rich. Someone asked me once what I thought about 8V92s vs. 6V92s.....I thought a minute,,,,"they are only 25% worse"... Terrible engines, everyone that has had them has woke up a lot poorer. Don't walk, run fast away from the boat....DD92s are just hand grenades waiting for the pin to be pulled. Everyone here has been sort of gentle about this, but I'm gonna give you the shot beween the eyes...They are awful engines, period.
Yo' Fren'
UV
Yo' Fren'
UV
-
scot
- Senior Member
- Posts: 1470
- Joined: Oct 3rd, '06, 09:47
- Location: Hurricane Alley, Texas
- Contact:
JP, yes the newer 4 strokes are more-better, in every aspect.
The effiencies are based on 2 factors, IMHO. 1) the newer engines are electronically controlled and fuel injection technology has come a long way. 2) All DD's lug around alot more weight (heavy castings)...takes more energy to move more weight. The new 4 cyl stuff is real light by Detroit standards.
It was a very long time before any other diesel manufactures came close to producing 1 hp per 1 cu, as the Detroit's did. The 3208's are 600+ cubes and many fly apart above 400hp, yet the 3208 is considered an all time great? why?, because most of them were set up at 375hp and below. At 325-375hp they "were" great weight-to-hp ratio engines. Below 325hp they last forever. The lower the hp per cube ratio, the longer the engine will last. 10,000-20,000 hours is do-able with either a 260hp 3208 or a 280hp 671, they both live short lives at 450+hp.
UV, your 6B's are set up at .69 hp per cu in, otta last forever.
The basic problem with the 92 series was/is they can produce a lot of power for their size, displacement and cost. This caused engine assemblers to "go for it" and many pleasure duty marine 92 series engines are set up too high. "If" an 8V92 series is set up at 450hp it will go a long, long time....but at 450hp it's a fat, heavy slob when compared to a Cummins 6C or equal.
It's typically a function of "when" most 92 series were installed in boats. Back-in-the-day if boat builders wanted 700+hp they didn't have many realistic options that people would pay for.
The effiencies are based on 2 factors, IMHO. 1) the newer engines are electronically controlled and fuel injection technology has come a long way. 2) All DD's lug around alot more weight (heavy castings)...takes more energy to move more weight. The new 4 cyl stuff is real light by Detroit standards.
It was a very long time before any other diesel manufactures came close to producing 1 hp per 1 cu, as the Detroit's did. The 3208's are 600+ cubes and many fly apart above 400hp, yet the 3208 is considered an all time great? why?, because most of them were set up at 375hp and below. At 325-375hp they "were" great weight-to-hp ratio engines. Below 325hp they last forever. The lower the hp per cube ratio, the longer the engine will last. 10,000-20,000 hours is do-able with either a 260hp 3208 or a 280hp 671, they both live short lives at 450+hp.
UV, your 6B's are set up at .69 hp per cu in, otta last forever.
The basic problem with the 92 series was/is they can produce a lot of power for their size, displacement and cost. This caused engine assemblers to "go for it" and many pleasure duty marine 92 series engines are set up too high. "If" an 8V92 series is set up at 450hp it will go a long, long time....but at 450hp it's a fat, heavy slob when compared to a Cummins 6C or equal.
It's typically a function of "when" most 92 series were installed in boats. Back-in-the-day if boat builders wanted 700+hp they didn't have many realistic options that people would pay for.
Scot
1969 Bertram 25 "Roly Poly"
she'll float one of these days.. no really it will :-0
1969 Bertram 25 "Roly Poly"
she'll float one of these days.. no really it will :-0
John,
Stop jerking around and get a real DD mechanic in for a real engine survey. A good complete engine survey should take at least 5 hours depending on how long it takes to get to open water for the WOT loads tests. Sounds like the guy that did the hull also made some engine observations. I would get a full blown engine survey.
Stop jerking around and get a real DD mechanic in for a real engine survey. A good complete engine survey should take at least 5 hours depending on how long it takes to get to open water for the WOT loads tests. Sounds like the guy that did the hull also made some engine observations. I would get a full blown engine survey.
Got the full engine survey done today. Mechanic said the engines looked great, ran well, fuel filters looked "like new" and he would rate them an "A". He thinks it is an issue external to the engines, e.g. props, but the fact that running them up in neutral goes to 2400+, but not 2600+ tells me there is something going on in the engines as well. Am looking for the DD genius, but in interim we are going to haul her on Thursday and look at the props and the bottom. Also, talked to a different mechanic that used to work on her 3-4 years ago and he said she was a 30-31 knot boat at the time. Frustrating.
Re: Sea Trial and potential problems with a Bertram 50
You have to see for yourself, slightly dirty props is all it takes....good luck with it.jgentry wrote:Boat hull had been cleaned 2 days earlier.
Nic
Hull No. 330 1963 SF "Tennessee"
Trust but verify.
I guess by buddy was right. Get the best hull and engine surveyour take them at their word and be there to go over everything with them anyway.
What a shame, your at the end of the process and need to start at step one again cause there is doubt that the hull and props are in good order. What a pain I really feel for you. Hope it works out.
Now I would wonder how the boat ran 30-31 knots...
I guess by buddy was right. Get the best hull and engine surveyour take them at their word and be there to go over everything with them anyway.
What a shame, your at the end of the process and need to start at step one again cause there is doubt that the hull and props are in good order. What a pain I really feel for you. Hope it works out.
Now I would wonder how the boat ran 30-31 knots...
-
In Memory Walter K
- Senior Member
- Posts: 2912
- Joined: Jun 30th, '06, 21:25
- Location: East Hampton LI, NY
- Contact:
Walt is right. Bertram book says 735HP 50B 24kts cruise 27kts WOT.
I don't know what the NO Load number is; but if it can't make No Load at the dock then it will turn up right under load. Is No Load is 2600 and the mechanic was ok with 2400 then I would not pay him. An engine surveyor should know what the correct number should be. If the boat only comes up to 2000 under load something is really wrong. Next question is how long have the motors been in an overload condition? Maybe it is time to look at another 50B. Next month I will be helping to run a 50B back to NJ. It has Mans. You can buy a nice 50B right and maybe this one is not the one.
I don't know what the NO Load number is; but if it can't make No Load at the dock then it will turn up right under load. Is No Load is 2600 and the mechanic was ok with 2400 then I would not pay him. An engine surveyor should know what the correct number should be. If the boat only comes up to 2000 under load something is really wrong. Next question is how long have the motors been in an overload condition? Maybe it is time to look at another 50B. Next month I will be helping to run a 50B back to NJ. It has Mans. You can buy a nice 50B right and maybe this one is not the one.
So here's the most recent update. Did the survey today and swapped the existing props with had some coral type growth on them(not a ton), for clean, balanced props the owner kept on board. Both sets were 28x31 3 blades. Bottom was clean and we scraped shafts clean as well. Had been told by mechnic that primary filters were clean but did not know status of secondary's so we swapped them for new. Lastly, we put 100 gallons of new fuel in forward tank.
Took her out and ran her. Same speed at 1850 - approx 20-21knts, but instead of topping out at 2000 rpm's she broke 2200 on port and high 2100's on starboard. Top speed was 25.7knts but she was averaging around 25 at WOT. She ran this way on both fuel tanks (we switched mid way - old fuel in aft tank, new in forward tank). Throttle was not pegged at the 2200 reading, still a few inches to go and no more increase when pushing throttles forward those last few inches.
Found out she did 2290 at WOT when current owner purchased her 4 years ago and owner before that had her running up to 30knts ( i tracked him down and he verified - but he was a shipyard owner and had her in perfect condition).
Feeeling better that with some care, attention, and use (boat has been used very little last year or so) we might be able to get her up to where she should be, but we are still worried about pulling the trigger.
Any thoughts would be appreciated and thanks so much for all the feedback to date.
John
Took her out and ran her. Same speed at 1850 - approx 20-21knts, but instead of topping out at 2000 rpm's she broke 2200 on port and high 2100's on starboard. Top speed was 25.7knts but she was averaging around 25 at WOT. She ran this way on both fuel tanks (we switched mid way - old fuel in aft tank, new in forward tank). Throttle was not pegged at the 2200 reading, still a few inches to go and no more increase when pushing throttles forward those last few inches.
Found out she did 2290 at WOT when current owner purchased her 4 years ago and owner before that had her running up to 30knts ( i tracked him down and he verified - but he was a shipyard owner and had her in perfect condition).
Feeeling better that with some care, attention, and use (boat has been used very little last year or so) we might be able to get her up to where she should be, but we are still worried about pulling the trigger.
Any thoughts would be appreciated and thanks so much for all the feedback to date.
John
So hull was not "clean" as you were told....all other information from that source is worthless....check everything.jgentry wrote:had some coral type growth on them (not a ton)
Original factory issue were 28 x 30 I think you will find...check with Bertram, if so boat is/always was overpropped.jgentry wrote:Both sets were 28x31 3 blades
You are talking about the cables...what about on the engine? That is the only place it means anything. You need to get a proper DD mechanic on the job, check everything incl. injectors, exhaust gas temp. (overloaded?) and exhaust back-pressure with a mamometer (overloaded from day one?)jgentry wrote:Throttle was not pegged at the 2200 reading, still a few inches to go and no more increase when pushing throttles forward those last few inches
You can take it that was maximum in ideal conditions, ideal is 2350+ in loaded condition...She always was overloaded.jgentry wrote:she did 2290 at WOT
Means absolutely nothing.jgentry wrote:had her running up to 30knts tracked him down and he verified - he was a shipyard owner
Obviously the boat is real cheap otherwise you would have walked. Over twenty year old 892s, overpropped forever, overloaded....you are looking down the barrel of pulling them out and re-building or replacing them...and while you are at it, no doubt, spending real money on the rest of the boat...if you feel like pulling the trigger on this one just do it, go with your gut...just take your wallet too.
Nic
Hull No. 330 1963 SF "Tennessee"
I don't know if I'd runaway, but before buying the boat I'd take into account you'll need to do a major overhaul or change out the motors in the not too near future.
I say this because your providing the boat is either overpropped and the longevity of the engines is comprimised or the boat is under propped and still can't spin up to the correct WOT so the engines are already tired. That is unless the surveyour or mechanic missed something in which case you need to find better ones. I'd also wonder if the props you put an are correctly marked and in good condition, I'd also wonder about the condition of the ones you took off. Thinking about it the "mechanic" checked primary filter but didn't check the secondary...find a good DD marine mechanic.
I'd opt to spend the money now and get some real good advice or be prepared to spend it later.
I say this because your providing the boat is either overpropped and the longevity of the engines is comprimised or the boat is under propped and still can't spin up to the correct WOT so the engines are already tired. That is unless the surveyour or mechanic missed something in which case you need to find better ones. I'd also wonder if the props you put an are correctly marked and in good condition, I'd also wonder about the condition of the ones you took off. Thinking about it the "mechanic" checked primary filter but didn't check the secondary...find a good DD marine mechanic.
I'd opt to spend the money now and get some real good advice or be prepared to spend it later.
-
Brewster Minton
- Senior Member
- Posts: 1795
- Joined: Jun 30th, '06, 07:44
- Location: Hampton Bays NY
- Contact:
Who is online
Users browsing this forum: Google [Bot] and 17 guests