Greetings,

I searched around on this, but couldn't find anything. I have a boat with twin 1990 5.7 EFI engines from Mercruiser High-performance. They have printed on them "Custom built by the Mercruiser High-Performance Division". I don't know exactly what that means. The starboard engine got water in it, so I've pulled it and am taking it to the machine shop. This machine shop works on Mercruiser motors all the time, and often do rebuilds for local boat shops.

The question I have is about parts. When I say parts, I'm talking about internal engine parts - bearings, pistons, rings, seals, gaskets. I asked one guy at the shop if they replaced the parts with genuine Mercruiser, or at the very least "marine" engine parts. He said he didn't think so, he thinks they just use normal Chevy 350 parts. I've heard from some that you MUST use "marine" grade parts, but I've never gotten any detail on exactly what that means. I know it means not to use a regular alternator, but that's bout the extent of my knowledge. I know marine engines run at higher rpms for longer than a normal engine, so it makes sense that the internal parts might not be off-the-shelf Chevy parts.

So my question is - is it okay for the shop to use the same parts they use in every Chevy 350 rebuild, or should I insist on Mercruiser parts, or "marine grade" parts? Or, is it okay for the internal engine parts to just be regular 350 parts? When folks here in the forum have a shop rebuild their engine, do they specify what kinds/brands of parts the shop uses?

Thanks!
Stan

Most parts inside that engine are GM parts. Mercruiser isn't making pistons and crankshafts, etc. So, as for your internal parts, GM or aftermarket is fine.

If its a black Mercruiser engine, then all internal parts are GM.
Most aftermarket parts are as good or better than what was in it to start with.

May want to recommend that they use marine quality gaskets. Heads for sure.