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Guys it has come to that time the old 504's gotta go. I have a shot at a couple of 6B370's is that too much for a '31? Thanks

330 is starting to push the limit, 370 is way over the top...

what price is a "shot" and most important what year are they . if they are cpl 1975 like mid 1995 then there is a way . only differance between 330 hp and 370 is calibration of the p 7100 fuel injection pump.

I agree.."what's a shot?" Are they a really good deal?

Bob, as you stated I think it is only the fuel metering plate in the pump...$100, and can be changed without taking the pump off, or apart. Plates come in sizes listed by #8, #10, etc. and are swapped in-and-out of the 94-98 6BTA truck motors all the time (which are also 12V 6B engines & run the P-7100 Bosch pump) Know in the truck circles as "the big pump".

Not sure about the injectors, the 370HP marine injectors are a very popular addition to the truck motors, that'll wake up your old Dodge lol.

I will add that those engines are easy and cheap to de-tune, or add power.

I'm talking from diesel ignorance, just having a gas engine background.

My thinking is...all things being equal, you would normally pay more for a higher HP motor. So no need to spend extra bucks for something you can't utilize. But if a motor of the same type can be gotten at a real attractive price...less then a lower HP version...couldn't it be used without a problem??? Dial it in with an under-propped wheel and just let the motor have an EZ ride...maybe a governor set so you cant' over rev.


Or is it that if a diesel isn't working hard enough and you'd get build up...

Or due to the higher HP, the injectors are setup to flow more juice, so you would lose economy?

Inquiring minds want to know...okay maybe just me.

I know when I rebuilt my cars motor, going from 180hp to over 400hp...if I didn't punch it, I got much better economy...15-16mpg to 22mpg

There's a B31 here in Puerto Rico that has Yanmar 480. They had to make tunnels for the props to fit but it runs the same as with the Yanmar 315.

the injectors are exactly the same on the storm block cummins between 330 and 370 hp . ok lets talk about rated power output curve. the 330hp cpl # is rated at 2800 rpm and the 370hp is rated at 3000 rpm so let put the 370 at 2800rpm ------yep look what we have now 352 hp .you know and i know you would very rarely run at wot. so lets take it to maximum torque ratings where our best economy would be. well wel look at that 260hp at 2000rpm ---hmm reality setting in!!! so he bumps it to 2200 at around 285 hp ---perfect that is what he will be running at 95% of the time.he takes advantage of the torque at 2000 to 2400 rpm by cupping the hell out of the props and still sit at 3000 wot. and the engines will last until his kids retire at 2200. but if he ever has the need for speed water permitting he has it at 2800 still at least 7% under the pin--------buy it if storm blocks (2005 or newer)---run

micky wrote:There's a B31 here in Puerto Rico that has Yanmar 480. They had to make tunnels for the props to fit but it runs the same as with the Yanmar 315.

EXACTLY..........

Spend an EXTRA 35 to 50 grand to accomplish with over-powering what can be done with the correct power in the first place.

KISS principle presides.

Dial it in with an under-propped wheel and just let the motor have an EZ ride

Which equals and easy, long life.

Yes. IMHO that is the correct mind-set for setting up the boat with engines that have more power than the hull needs. The power is not required, but as Bob stated about a 6B diesel, that can perform well at 2200...

the engines will last until his kids retire

"IF" there were any engine weight difference (penalty for the power), or required major hull mods, like pockets..it would be a different conversation, with other factors coming into play.

scot; same weight , same identical motor except fi pump. use same shafts as 330 , same gears same props just a 1/2" more pitch.again this is you getting the engine discounted .
capt. patrick the installers just don`t have the total picture in PR. you want to run big block yanmar at 440hp and be the baddest no problem but you going to spent big time over a conventional 315hp yanmar set up . prop pockets are absolutely useless unless you run custom 6 blade full cup props or you are that idiot in the fast car stuck in the mud with bald tires just slipping away. those pockets "steer" the water (all agitated) into a small area were the props are thus the conventional prop lose all there" thrust " you must get all the metal you can in density like 6 blade props . i could be wrong in theory but that would make luhrs,buddy davis, viking, merrit,cabo wrong also!!!those props cost a fortune, i will photo prop pocket setup when i get a chance.

No reason to photo cause its all a waste of time and expense.

Any other reason is a load of crap, sorry.

If the original OP can get the set of engines cheaper than a set of 240 to 330hp engines, then that would be a far fetched semi valid reason to get them realizing the full potential would never be realized and any fantasy thinking of making them last for 1000 years cause they're under utilized is just plain silly.

bruce don`t blame me i told you a while age i could get one 440 hp for free and one dirt cheap and still would not do it because i don`t like cutting the bottom of a perfect boat. however to use a 370hp cummins in lieu of a 330 hp by cutting back a little bit to improve enconomy and best cruise speed for water condition. i am 100% in favor and if the price is real good sent me the p7100 and i will have them converted for two thousand with warrantee to 330hp. if the price is right jump on it . lets leave the conversation of 440/480 hp out . this is really going out of your way in plain common sense just resell and by something more suitable.

Gentlmen thank you for your input.
Last night at the old watering hole the deal was killed. Here is what we had in the works. The engines had roughly 800hrs on them since a major overhaul in 37 Bert. They've come up from FL and fished off shore at 16kts too slow for the owerner so he wanted to go bigger. The price was $10K-$12K for both with gears. Well he decided to wait maybe another year leaving me with no option other than to start feverishly looking for power. I called Cummins and they are over my head $20K ea with gears.
If anyone can point me in right direction on a pair of horses it would be appreciated

tony that exactly why i posted the article.twelve thousand compare to forty thousand leaves you room to sent fuel injection pumps directly to bosch. they mount it on a fancy 300,000 machine and give it back perfect and if you want to drop lower to 270hp simply remove raw water output on top of sherwood pump leading to aftercooler then buy block coolant output unit and use to cool aftercooler.you also are removing raw water fuel cooler this way. another words if you get another deal on 370hp cummins with gears don`t past up.

scot incidently cummins says regarding 6bta-m-3 one hour in nine at wot eight hours out of nine should be ran at up tp 10% off pin. cummins 6bta m-3 330/370 hp are rated for longivity before rebuild by the amount of fuel that flow in to engine for combustion.rated at 30,000 to 33,000 gallons of diesel fuel before rebuilt (thats if you have half a brain and put safeguards to prevent overheat) you would according to cummins increase the life of the engine dramaticly by backing off at least 7% . so if you have a situation going offshore loaded to the snot with 6 big beer belly guys and a cases of beer in the hole in addition to full tank you can take the rpm up a notch to maintain the enconomy speed. what the hell you have hp. in reserve!

Bob,

I did know that they rated rebuilds by fuel burned and it creates some interesting comparisions.

A boat would look something like this; 30,000 gals \ 8 gph = 3,750 hrs before rebuild.

The 6B in my truck would look something like this; 30,000 gals x 18 mpg (avg) = 540,000 miles before rebuild.

That works out to be fairly accurate, in both the boat and the truck. Both can do more hours if well cared for. I have seen 6B's in boats for sale with 8,000+ hrs and 6B's in Dodge trucks with 800,000+ miles.

So 3,750 hrs on a boat's engine works out to something like 540,000 miles on the road....based on the manufacture's std of "gallons burned"

I think that math is correct, with eye-popping conclusions as well.

Scott, an upside to your 3750hrs is...not many people start up a boat and hit cruising speed for x amount of hours then shut down.

Engines eat hours with warm ups,, cool downs, put-ting (sp?) in and out of harbors in No Wake conditions...then there is the Howdy cruises and trolling...I eat lots of hours trolling, much less burn in those conditions while still eating up the hours.

Scot,It was my impression that the Cummins 6bta was not rebuild able. After the allotted hours the cylinders would go egg shaped and since they could not be sleeved new engines would be needed. Is this miss information, Or can the Cummins 6bta be re built?...Russ

yes it is providing you did not cook it. incidently it is the pistons that wear first. you purchase 6 piston assy. consisting of piston,pin,connecting rod and all new bearings. some overbore .020 and put in .020 oversize pistons.there are other methods . wholesale rebuilt kit is 1600.00.

Speaking of engine hours........I worked at a Mack Truck dealership in the early 70's.

The question about Engine hours vs Clock hours came up in one of our discussions. In those days the tachs recorded hours were mechanical driven by a cable.

The anwer was a Tach hour matched a Clock hour at 2100 RPM.

I can understand the Fuel Burn method but 3750 hours sounds very very low....like Scot said.

I understand that the engines I rebuilt for DeNada had 5600 hours on them when I purchased them from Dan.

If the exhaust elbow had not failed I feel certain that those engines would have ran for several thousand more hours. The pistons still had the machine marks in the skirts.......the piston and cylinder bores measured within servicable limits......but the rod bearings were showing pretty good wear....the Babbit was worn thru into the copper.

The only "Real" failure was the Crankshaft Thrust bearing on the port engine.....but it was a cheesey design to start with.

With a little TLC I believe these engines will go 10,000 hours

hb

6bta diesel wear usually consist of the pistom rings first but the ring lands also wear so the best method for a rebuilt engine is 6 new assemblys in kit the engine may get by with just breaking glaze and rehatch cylinder walls but slight overbore really is the cats ass. very easy engine to rebuill and so cheap in comparison to other diesels because there are two million out there.so complete assembly kits are readily available with updated plama piston rings and updated piston crown.

harry they go 20,000 hours in a generator on a regular basis . the marine world is the most abusive by far like a tractor trailer going uphill under full load with the pedal to the metal . then again how many of us can put those kind of hours on a recreation fishing boat motor. would be 20 years or more for most of us.