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  #1  
Old 07-17-2004, 10:04 PM
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Diesel Engine for Marine Use

I'm researching my next project, replacement of a worn out 302 in a 28 foot wellcraft.

I want to go diesel as the stock 302 required premium fuel and at 2+ bucks per gallon, a weekend on the water skiing can cost a few hundred bucks!

I've considered VW engines bu tthe 4 cylinder is way off in power and the TDI 5 cylinders are expensive.

Some considerations I am pondering:

Ability to use SVO/WVO or biodiesel.
Longevity
Tunability (200 horsepower?)
Weight
Cost (to Some Extent)


I've looked into american iron, but the powerstroke or cummins 5.9 are too big and too heavy.

I've got a a 3.0 liter 5 cylinder iron head engine out of an 85 126. But am also looking at using a diesel from a 91 350, or even a 3.0 6cylinder, however I have heard the aluminium heads have had problems.

Anyone have anyt comments on the engine mentioned above?

I am considering a turbo swap and fuel mods to yield 200-250 horsepower out fo the engine I choose. Anybody know a good tuning shop for pump/injector mods?

Thanks,
Scott
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  #2  
Old 07-17-2004, 10:43 PM
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Converting automotive engines for marine use has never worked they are just to different. I sudjest a 6cy Yanmar in the 250hp-300hp range with a Volvo Ocean series outdrive, their plastic so no corrosion. This sounds like a $20k project to go diesel, you will at least need new tanks and fuel lines, if your boat is an inboard, a new shaft might be needed, a new prop is a must and with the larger shaft a new stuffing box and larger strut bushing, or a new strut. Also the exhaust may have to be made larger. It might be better to just buy a new ford long block. Although depending on the condition of your boat it could make sense($$$) to repower with a diesel. Diesel boats are hard to touch under $80K and they will have old 1,000+ hour diesel's. You could have a nice new diesel in your boat for $20k-$25k, if you like your current boat this could be a good way to go. Also if you use your boat a couple hundred hours a year, a diesel could pay for it's self in the long run. Not to mention the resale value. Talk to someone who has done this before to similer boats, that way you will get first hand knowledge and experiance.

btw stay away from the Mercruiser diesels they are having huge problems. Volvo's are a pita to get parts for.
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Old 07-18-2004, 12:28 AM
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Consider the Olds 350 diesel. It's roughly the same size and weight as a 302. And I know that some were marine use.
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  #4  
Old 07-18-2004, 11:32 AM
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Wasn't the GM 350 diesels reliability scetchy at best? I've spoken with a retired technician who worked on thsoe cars durign the day and he said they were crap. Crankshafts and headgaskets were always needing replacement.
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Old 07-18-2004, 11:46 AM
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"Converting automotive engines for marine use has never worked they are just to different."

What? You are kidding right? What do you think every marine V8 gasser boat engine is? Nothing but car engines with different cams, watercooled exhaust, etc. There are some specific changes to things like the freeze plugs to less corrosion-prone metals and thick layers of anticorrosion paint but they are the same blocks and internals. A Yanmar conversion makes sense but ain't cheap. The only light V8 diesel readily available is the GM. These guys http://www.peninsulardiesel.com/ do a marine version. What I am suggesting is find a GM diesel truck motor and buy the parts from them to convert it. Look under the marine kits link. Or just buy one from them. RT
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Old 07-18-2004, 12:06 PM
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Well you marked off the one I had in mind, the Cummins 5.9L 6BT. I do suppose it is fairly heavy but also can handle insane amounts of power (550hp, ~1300ft-lbs stock motor) to help offset its weight. The marine version weighs about 1100lbs.

If it were me I'd remember to forget the GM 350.
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Old 07-18-2004, 12:18 PM
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The reason didn't mention the Cummins is the weight. Great motor, no doubt. The GM diesel weighs the same as a big-block chevy which makes swaps simple. RT
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Old 07-18-2004, 12:47 PM
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Re: Diesel Engine for Marine Use

Quote:
Originally posted by scottycboy

I want to go diesel as the stock 302 required premium fuel and at 2+ bucks per gallon, a weekend on the water skiing can cost a few hundred bucks!

Skiiing behind a diesel? I don't thing you can get the acceleration, can you? My perception is that diesels are slower to get up to cruise RPM's. At least mine takes a while with Detroits.
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Old 07-18-2004, 02:25 PM
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Yeah, I would definitely find a SUCCESSFUL diesel-powered ski boat and do what he did......
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Old 07-18-2004, 03:07 PM
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Hatteras,

I think $20-25K for a conversion is way low if you have to change out shafts, tanks etc., and you go with a new engine. You could go with a fairly young take out and save some.

I priced re-powering mine a few years ago with Cummins or Yanmars and the cost was approaching $80K turnkey. That is a lot of money for about 5-6 extra knots per hour.

Assumming Scottcboy's project would cost $30K vs about $5K for a rebuilt gas engine, it would take him about 1250 hours of use to make up the cost. That is about 15-20 years of average use.
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Old 07-18-2004, 04:38 PM
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rwthomas1 yeah the blocks and maybe the cranks are the same. You can probably buy a long block 302 Ford marine engine from a place like Recon Marine for less $5k give or take.

$25k is probably a little low huh? $35k is probably more on the mark, I'm assuming he is doing all of the work himself.

Cummins makes a Marine version of the 5.9 I think.
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  #12  
Old 07-18-2004, 04:59 PM
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Nissan Diesel

try here. They list Nissan Engines available for both industrial and Marine use.

http://www.jescoweb.com/nissaneng.htm
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Last edited by coachgeo; 07-18-2004 at 05:05 PM.
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  #13  
Old 07-18-2004, 05:24 PM
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www.yachtsurvey.com

Read the sections on gas vs. diesel.
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  #14  
Old 07-18-2004, 05:27 PM
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Avant Salvage can set you up with a used 6.5 TD long block with low compression pistons for I think about $2800.00 It has a warranty. Peninsulars conversion kit I am guessing at $5000? Used Bravo outdrive $2000-$2500. Assuming all work done by owner, total cost @ $10K. Could be alot less if you source your own block, have the machine work done, low comp pistons, etc. You could also source a Cummins out of a wreck. Ebay all the non-marine bits, bolt on the marine stuff, then the used Bravo, etc. There are deals to be had. Buying new when it comes to repowering older boats is simply not cost effective. RT
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  #15  
Old 07-18-2004, 05:53 PM
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Quote:
Originally posted by fahrgewehr2
www.yachtsurvey.com

Read the sections on gas vs. diesel.
Great articles, although I question some of his data.
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