Mercruiser - marine parts vs auto parts

[Dave2]

Hi again all,
I've had a hiccup with my "new" GM 5.7l reconditioned marine long block (which replaced my 1998 Mercruiser 5.7l EFI). I will need to replace the following items:
Pistons and rings (standard size)
Exhaust and intake valves
Can anyone advise me whether the automotive equivalent of these components may be used? I know that marine engines are exactly that i.e. marine engines but I dont know what makes an engine a marine version rather than an automotive one. Are the abovementioned components any different in marine engines versus automotive engines?
Cheers
Dave

 

[[2068]]

The differences between marine and automotive are normally outside the block, so electrics, manifolds, alternators, injection, exhaust etc. are different. I would guess (but I'm not sure) that on the 5.7 the pistons and valves would be exactly the same as on the automotive version.

dv.

 

[David2452]

May they be used? Yes. Are they the same? No. you pays your money & takes your choice.

David

 

[chuckaduck]

try ferrari pistons of cricklewood london
they sell engine stuff ie istons valves rings

 

[spannerman]

When I rebuilt my V8 I worked for the local Mercruiser dealer and even with staff discounts the prices were exhorbitant, so I went to my local american car specialist and bought everything from him for half the price. The only thing to be aware of is if its is sea water cooled you have to have a Merc head gasket with stainless inserts or the salt will eat the ordinary ones away, also a Merc water pump so as to have a seal which will not corrode. No probs if its freshwater cooled the standard car parts work fine, mine is still running sweetly 4 yrs later with its new owner.
I used flat top pistons to raise the compression and a sport cam, the time spent with a Dremel tool removing excess material around all of the valve guide boss's in the head and gasket matching really paid off ( place the inlet and manifold gaskets on the head and valley manifold and see how much metal overlaps the size of the hole in the gasket, scribe around it and you can safely grind it back so that the air flow is even as it goes from the manifold into the head), same applies to the exhaust manifold. It ran incredibly smoothly at idle and ran much better than when it came out of the factory.

 

[mriley]

You might like to have a look at a US forum run by the excellent boat parts company Boatfix. It's called 'Boatered.com' (select the engines etc forum) - there is usually a debate over marine vs auto. The last one I saw was discussing GM 350 (5.7l) auto vs marine components, it is dated 3 Dec 05 and you can still access it (select 1 year's worth of posts and go to around page 25). That question received 59 posts in reply - I don't know if there's much more to add to the debate.

 

[Dave2]

Thanks everyone for your advice. I live in the Middle East and the Mercruiser parts prices are extremely high. I will have all the original mercruiser accessories and I will only replace those items I listed above with the auto parts. Everything else including replacement gaskets etc will be mercruiser.
Thanks again.
Dave