Your asking a loaded question.

Here's your answer with regards to small light fast boats (as compared to a 50' Hatteras) and my personal feeling below that: You need more gas power than that and you need more cubic inches. You can't run a gas engine as close to peak as the diesel for as long. The 365 Merc's or something similar with fresh water cooling run slow to never exceed the same 50-55 mph would I think last as long as the Yanmars. Maintenance costs will be slighty higher but minimal.

My thoughts - I feel with today's advancements in gas engines that for smaller boats they are as good as any diesel engine. These small diesels don't have long life like the old 6-71's, the cost of diesel fuel is insane, and gas engine economy is sooo much better than years ago. The more electronics they put on a gas and diesel engine especially going forward make both engines susceptible to non-iron (iron would be piston, cam, valve, etc) related failure.

The longevity question is what people hang on when talking about switching to diesels, but you'll never wear them out in a go fast boat - period. People get bored of the go fast boats in under 3 years generally so they're sold /traded off or sit somewhere to be used when they want a thrill.

I can buy a gas boat new for much less than diesel and run the piss out of it. When I wear it out I'll come close to being able to put in 2 sets of replacement gas engines (stock power) with the money I saved on the purchase up front and the fact that diesel is almost $1 a gallon more in some areas.

Safety wise diesel can't be beat, diesel is hard to explode, gas is easy.

My Mercury outboards 225 Opti's are part of the class action suite, people call them junk etc, etc, etc. I put over 1,000 trouble free hours on them, no repairs nothing except a blown powerhead caused by a Merc Tech checking something on it for a Mercury recall and Merc ate it for me - pretty good for outboards!!!

After all that I still like the diesels better, the sound, the power, the fact I can run the boat harder longer for the same Hp. Cost wise though, they don't prove out.

Joe Gere

I will buy everything your saying Joe.

I am still not convinced that you are going to get a ton of troublesome hours out of these high RPM diesels.Whether it is a gas engine spinning at 3800 or a disel spinning at 3800 the rotating masses are essentially the same.

Everyone forgets what made a diesel so reliable and that is the fact that they where making huge torque and power at very low RPMs.

To get back at my original comparison lets pit a 315 yanmar against a 330hp 454.

I gotta believe that a 454 will live forever at 3600 and be making very comparative torqe and horsepower.

I know the Yanmar is going be burning 13-14 gallons an hour.What do you think the 454 would burn I bet it would be real close.

Back in the day we all ran 454s in the parasail boats and are average burn per an hour was 8 gallons.This is speeds all over the spectrum over a year of running.

Than out came the little Volvos that were going to be the new fuel saving miracle.Guess what the fuel burn difference from the gas was barely discernable.The Volvos had to run almost full throttle to to do the job that the 454 was doing at 3000rpms.

And the reliability what a nightmare with a turbo and a super and that stupid clutch on the super that lasted maybe 300 hours if the motor was ran all over the rpm range constantly.And the real kicker was if the motor didn't toast they just flat wore out and lost so much compression at a thousand hours that the motor lacked eenough power to do the job.

Not beating up on you just discussing.

What do you think should be the life span of a Turbo for failure and or rebuild ? Also the injection pump and injectors?

Your not beating me up, I agree with your points, I love to debate these things - that's how we all learn new things.

Many of these new small diesels are throwaway in nature and when put into an extreme environment of higher Hp, higher constant rpm, constant load and extreme temperatures they don't last up to customer expectations.

How long should a turbo last? As long as the engine bearings.

I would expect a well designed water cooled marine turbo to last into the 8,000 hr range if it had clean dry salt-free air, didn't get mositure up in the exhaust pipe etc. I don't think marine turbos fail from design problems of the turbo as much as installation and environmental factors which can't be controlled in a boat like on land?

The other thing is acceptable engine TBO's, what is it on a small boat? 2,000 hrs, 5,000 hrs or 10,000 hrs?????

If you have the same little Cummins B block that is 480Hp in marine trim on a genset set it truns 1,800 rpm's and puts out about 120hp that's it. You expect that to make close to 10,000 hrs before you touch it.

Injectors usally last till overhaul now a days on a truck. Again, don't think they should need to be touch on a boat until overhaul time? In a boat you have extreme fuel temperatures that you won't have in a truck or gen set, that might contribute to lower hours between failures???

Joe Gere

Thanks Joe for the reply.


I won't even comment on the Volvos because those were a complete disaster but I here they have a new model that is the one .


I am just trying to relay My experience with those small diesels.I got 4000 hours out of my Yanmar But I had 3 turbos at 2400 a pop one injection pump at 2800 2 exhaust manifolds at 1800 one oil cooler at 1200 and a tranny at 2000 because the cooler failed.I figure I had about $40.000 into it to get thoses 4000 hours.

My 454 I put 3 sets of risers and 1 set of manifolds a couple waterpumps a couple circulating pummps and a fuel pump and a Carb rebuild and a couple sets of plugs and distributor caps.I had maybe an addiotnal 2000 into parts over the initial cost of the engine which I think was 6000 for a grand total of $7000.

And the 454 never missed a day of work.I probally lost another $40000 in missed work with the diesel.

Just figures I am throwing out there.

Diesels have a place but, and I said this more than once they are not a miracle. The more Hp/cui the less time TBO.

I don't know your Volvo's but one thing to be careful of and that is saltwater cooled manifolds. When you look at some of the attempts out there to marinize the 6.5's and other small diesels people save weight and space by saltwater cooling the manifolds and or turbo's.

The high exhaust temps boil that salt right and the more salt the more thermal insulation - the quicker they fail.

Freshwater manifolds should never fail unless you don't have DCA in the cooling water and you get cavation which causes holes?

I run an outboard CC for all the logic you expel here, blow a power head, $6,000 and your running again, lower unit $3,500 both brand new with warranty, DFI/EFI lets them sip fuel. Two new engines installed in under $40,000 and they give what 5-7 year waranties now??? What more could you want?

Joe Gere

Why was Buzzi so interested in making the Diesel work in his boats ? What was the real advantage ? Was there any real reliability out of them?

You have to look at the time at which Buzzi and myself were pushing to do diesels in go fast boats. We both had different agendas but the same goal, make money from the sales of pleasure applications

In the 80's when we both started playing with diesels on different sides of the pond offshore racing was 150-175 miles of open ocean. Look at any races from back then and you'll see that 2/3 of the boats didn't finish the race. Read some of 7x posts and you'll see, Richie was there from the earliest of days. Gas engine boats had the old Hilborn/Crowler type fuel injection units, they delivered poor fuel distribution, could only be run at near wide open - many problems with gas engines in general related to control of spark and fuel delivery compared to today.

Don't forget there were no aftermarket manufacturers of BIG cui GM style blocks, heads, cranks etc and Class 1 was limited to 1000cui total! The engines ran very high compression to make the power they did - add that all up and you see why most boats didn't finish the race.

I was comissioned back in 1984 to build a replacement to a gas engine for a 40' Monza!!! Eloy was uilding this 40'er and I had a customer that wanted to run at 60 mph with that boat but with diesel power. They wanted a boat to run back and forth to the Bahamas with (not a drug runner, wealthy garment manufacturer with a house there). At that time it was near impossible to do.

Buzzi and myself figured if you could take the inherent reliablilty of a diesel and put it in an offshore race boat you would win a championship if could just finish every race - period!

Buzzi went the way of Fiat we went the Navistar route. Buzzi eventually went purpose built engine "Seatek" with a drive system designed around the engine. We wanted to corner a repower market and use existing Mercury drives. Well you know who wound up on top there - and it wasn't me. We started with the Cummins B's about 3 years later than we could of - kick myself for that!

7x talks about the old days having spare engines and drives all around the world, that was racing, you needed to change engines and drives every race or else you didn't finish and even after that the odds of finishing were against you.

The Buzzi philosophy was this, my engines & drives can without fail last an entire race for 2 reasons 1) I have diesels & 2) I have more engines than they do so I can loose one and still finish with ease.

The cavet to that was - his boat waS mostly likely not the fastest. Buzzi could start the race and put the engines on the pins, run full out and never back off. If you watch his early races that was his plan get out front and make the gas boats have to push harder then they wanted too just to keep pace and not fall back, remember it's 165 miles of ocean not a dozen laps on the river!!! You could fall behind by miles in a race if you didn't keep up with the front runner. By the time the gas boats lighten up enough to be faster they either broke from running so hard or just plain didn't have enough miles left to catch him.

So your question of reliable equipment? Yes, at point in time the diesels and Trimax drives without question better than any gas engine money could buy.

Once again a wealth of information.Thanks Joe.