BajaRunner

Ive heard there are differences, but what about rebuilding a boat engine. can you use car parts? pistons and rings specifically?

Crazyhorse

Sure, as long as you use high-quality parts. Take SpeedPro pistons as an example. An L2399F piston really doesn't care whether it's in a car or a boat engine. The piston-to-wall clearance might be just a touch larger on the marine engine but the parts are the same.

puder

the basic parts are the same but some of the specs are different.

whn biulding them clearances are different. Cam specs are different. Like eth 502/502 cam in the 502 crate engien tends to casue reversion in a wet exhaust. YOu have to use brass freeze plug in eth block, Marine distributors, starters and alternators are NOT interchangeable. DO NOT run car parts in a boat. The marien version aredesigned not to create sparks. ANd if you get soem gas fume settled in yoru bilge and you have automotive elctricals parts possible BAM!!!!!!

also marine carbs have "j" tubes so any excess fuel from eth fule bowls gets dumped into the carb down into et engein as opposed to all over the place (half in eth engien/half ON the engine) with the standard overflow tubes.

BajaRunner

im with you on the alternator/starter etc. im just checking on piston and ring clearance

rmbuilder

Depending on the ring package, marine engines may require an additional .002-.004 top ring end gap. Aftermarket piston to wall clearance and gauge points will vary per manufacturer and material.
Bob

JPD Motorsports

sorry if a stupid question but why the larger ring gap on marine motors? Young mind wanting to know.

BajaRunner

I think its because these motors run cooler than car motors

rmbuilder

The larger gap is required due to the prolonged (relatively) high rpm marine engines routinely encounter. The .002-.004 allows for additional thermal expansion needed from increased cylinder temps that build under these conditions. It decreases the possibility of ring ends butting.
Bob

JPD Motorsports

Thanks for the aknowledge! Just goes to show how good oso really is

Crazyhorse

Funny thing, I just talked with JE Pistons this afternoon about end gap on my 4.500-bore supercharged marine engines and they said .022 on the top ring, .025 on the second. I would have guessed a little bigger than that but JE ought to know.