I know I have seen this issue brought up, but I can not find it.

Can you use a GM crate motor as a mercruiser replacement motor? Most directly I am looking for a pair of 502's to replace a pair of low power 454's.

Thanks for letting me pick your brain and for helping the not-so-technically savvy...

check peak engine rpms (might need to change cam, not sure), also will need a marine carb, flame arrestor, etc, and probably a few other things. im no specialist at all, just telling some of what ive picked up over the years

get ready for all kinds opinions ... but generally most would say no ... at least not right out of the box ..err crate ... wrong cam ...brass freeze plugs.. and some clearances are not right for marine use ...However ..If I was to usea crate motor. I would take it to someone I can trust than can go thru the motor and Make the necessary changes ..m

There is a reason Mercruiser's engines are so expensive, they are worth it!

The cam in a 454 or 502HO is OK but not great for marine use. Also, I have heard that the tolerances are not held as tight in a "crate engine".
1-800-runsnew sells brand new 435HP/502 marine base engines for the same or less than a 502HO crate engine; like $5200...

Will need to change the oil pan, as the crate motor is smaller than the marine version. Cam is different, but some have run it without issue. Waterpump different as well. Internally, same components as marine version on lower end.

I'm sure others will chime in with other differences as well. Can be used, but will need a few changes.

search this fourm for a thread called "ZZ 502 DUD questions".....check that out.......it will help you make up your mind......doug

I had a pair of 502s from www.1800runsnew.com and they were great!

Food for thought!

What has GM ever put the 502 in? Nothing I can think of.

Where do all of these 502s go? Mostly the marine industry!(?)

Note: Some things a different for safety reasons but mainly in the ignition, alternator, and carb areas because of the inclosed engine compartments and flame/spark/fuel control.

Get a merc shop manual and a GM shop manual for the big blocks and compare specs. For the most part they are the same. And yes even some DO use the same cams. Some do not.

Merc.$$$$$ GM $$

Just have to be aware of what the real differences are.

Everything I 've read says GM Crate motor to drop in boat = no. The 1800runsnew stuff look like the way to go on that.