Auto engine marinization

[woodboat]

My position on auto engines in marine applications: marine engines are engineered as continuous duty, auto engines are not. Marine engines also have various changes to address heat from working in a tight compartment as well as resistence to explosion. Differences vary from engine to engine but as an example my inboard has a different oil pan, valve covers, dipstick, intake, exhaust, carburator, fuel pump, block, crank, rods, piston, cam, distributor and alternator just off the top of my head. There isn't an inexpensive way to convert a standard car engine to a marine application. Also in your example the higher horsepower motor in all likely hood will not last as long as the lower model. It will be cheaper to buy a proper marine power plant and in the end it will be far more reliable.

[Corpus Skipper]

but as an example my inboard has a different oil pan, valve covers, dipstick, intake, exhaust, carburator, fuel pump, block, crank, rods, piston, cam, distributor and alternator

The intake, block, rods, crank, and pistons are all production GM, Ford, Chrysler, or whoever's engine is used. They all use factory high performance pieces which were available in muscle cars or trucks. The Crusaders from my boat were all original as from Crusader, and included a GM 350 4 bolt main block, 992 casting high perf. heads, forged steel crank, and Chevy "pink" rods, all of which were factory production pieces, and all still available from the GM performance parts catalog. Nothing extremely high tech. Cams are cams, with the exception of reverse rotation engines which are a special grind for the backwards firing order, and these engines use a gear drive instead of a timing chain to keep the cam, and thereby the distributor, rotating in the same direction. The new Crusader engines are all GM, right off the assembly line. There simply isn't a large enough demand for full "marine" engines for everything to be porpose built, when factory engines do the job quite well. Crusader bolts on wet manifolds, marine carb (or EFI), starter, alternator, and distributor, extra capacity oil pan, remote oil filter, paints it blue and sends it out the door.

[woodboat]

To clarify: In my boat those parts are different versus what was standard in a standard car. One could buy the HP parts such as the block with four bolt mains and make a motor suitable for marine use. My engines are old. Currently the HP parts are available in some cars making the GM parts readily available. So a "standard" hp GM motor can be suitable as a base. I have NOT researched the engine but do not think I would try to play with a BMW 2.5 TDS V6.

[Danielsan]

I am not shure either, at this moment I am searching for the adequate engine. I do find car engines with the HP I would like and with good torque running at 3000-4000RPM, but also found traditional diesel engines DAF, Perkins,... with lots of HP and even more torque at lower RPM 1800-2200 also much heavier, almost twice as much?
Those engines can run up for hours and hours on and on, I don't know where to put them? they are to long.
Not that it matters I still have to build the boat, but I need the extra space as I want to get 4-5 people sleeping on board, with little WC-Shower comp. LOA24.5ft, Beam 8ft, displacement 6200lbs fully loaded with 4 people waterand fuel,...

greetz,

Daniel Peeters

[PAR]

3,000 to 4,000 RPM sounds like a hunk of American iron to me. Big blocks spin their reciprocating mass even slower and all the metal flying around in a 454 or 572 develops big chunks of torque, which is what we want. Slow turning engines live longer, but generally are heavier.

As kids we use to build "stump puller" engines, basically as long a stroke motor you could do within the block with minor machine work. They spun up slowly, but pulled like crazy. It was difficult to break these motors.

The latest thinking is to use smaller engines to save weight and fuel and spin them up with appropriate gear reduction making the torque. I dislike the idea of a prop spinning the water to a froth and being asked to push a heavy boat. Using light weight parts inside light weight engines is a good way to increase the profitability in a powertrain generating a targeted output range. After the warranty period is over what do they care.

Give me a big wheel and a big, fat, low tech, highly reliable, easy to repair, plentiful parts, American push rod V8 of substantial displacement and the beast will pull hard, long and can be rebuilt when it's time, with over the counter parts. When you rub the rings down on the newer thinking engines, you'll run into interesting difficulties like porousidity in the cylinder walls because there isn't enough meat left. This happens on American V8's as well, but the block usually has been bored a few times and after say 70 to 90 thousands has been cut this will also be the case.

As a general rule, automotive engines can have a much higher HP rating, because it's only required to produce this peak output for very short bursts and amounts to a small percentage of the total time the engine operates. This isn't true with marine applications, where the engine must develop the peak output most of it's life. This is why the 350 CID Crusader engine produces 230 HP, but requires the "pink" (developed for racing) GM rods installed. The same engine built with the same parts would have a warranty from GM in one of their cars with over 400 HP and one could be expected to get 200,000 reasonably trouble free miles from it.

Marine engines are continuous duty, as are aircraft engines, stationary engines for pumps, generators and the like. They run up to their operating RPM, temperature and pressures and stay there, usually under full or near so loading. This is like a car, full of fat guys, pulling a trailer full to it's roof with bricks, up a 45 degree incline, having a driver making a dent in the floor boards with his right foot, it's whole life. The average automotive engine isn't up to the task, at least not for long. It lacks the HD parts, hasn't the necessary cooling, balancing or application specific components to keep from burning itself up.

Yes, you could build one, but the parts would eat you alive, because you'd be getting them without the huge purchasing power of a marine engine builder buying hundreds of assemblies at a time. Parts sales are where the real money is made by car companies and engine manufactures. Retail for them is generally 500% (no kidding . . .)

[Suede]

Ok PAR...so you belive that the "huge purchasin power of the marine industry" is the reason for the very costeffective marine engines.....sorry I don´t. Ok an aftermarket camshaft is more expensive than stock....but not by 500%...
Maybe your 500% is if you buy everything from a retailer as parts....but normally you start with a second hand engine...a a few parts are already in your toolbox.
On the other hand....if I should build an engine from parts from marine-supplers....500% would be a bargain......

rgds
Olle

[gonzo]

Pink rods are not different from the stock ones. They are pink because the factory tests them with die for cracks.

[Corpus Skipper]

Right on Gonzo, that was my point.

[Danielsan]

I am back

After all I might have listened to you guys

I made my choice. It will be a 6Cyl in line PERKINS diesel engine 150HP comming from a crane. RPM 2000 on and on and on,... torque I don't know but I am sure it wil be enough. No electronics, no turbo, just diesel, 24VDC, and fresh water and it turns (not forget OIL). Weighs some 300-400lbs more but that won't make me feel bad.

(Next step would be putting in a diesel V10 6L TDI 536HP engine with CPU made only for operating diesel pump-injection and turbocharger)

So the big block, traditional thing wil get in it first.

Now the next step(s)

Greetz,

Daniel Peeters

[tom kane]

The future direction of marine engines should be interesting,with the big engine manafacturers committed to aluminium V8 and V6 auto motors.This must become the basis for boat engines in years to come.Alloy motors, Fluid closed cooling,Comprehensive Engine Management Systems even checking on fuel leaks and saftey.Turbo and Tuned intake and exhaust Systems with emission controls.Computer Diagnistic and fault finding.If you have trouble at sea all you would have to do is to contact the engine manufacturers website,and they will be able to sort out the problem while you carry on fishing.The biggest down side would be that you would not be allowed to do the repairs yourself.

[gonzo]

One of the greatest improvements has been in lubrication. Modern oils last longer and reduce friction to a much greater extent. An old design engine running on syntetic oil will last at least twice as it did with a 60's oil.

[Danielsan]

Maybe this isn't the place to ask this but I will start over here.

Does any of you kan tell me what Is the avg. output rpm of a prop during cruising?

Thx in advance,

Daniel Peeters

[gonzo]

There is not such thing. Every design and installation have different RPM ranges.

[Corpus Skipper]

Perhaps this will help lay some debate to rest. As seen at www.ebasicpower.com. I had the actual page link, but my @#%$!! computer wants to freeze up. Guess it's time to give it another lobotomy.

[woodboat]

What is the picture supposed to prove? Is the picture of a 2 bolt main Chevy small block mean we can all rush out and marinize our V6 ford out of a Taurus with good results? American V8s are some of the most durable gas engines available. So what. I have used an engine out of a nova in a boat. That doesn't mean I would recommend something just because I did it and lived. Heck, who's engine is that so I can never buy one?