502 MPI Issues
 

Hello everyone here. I want to share my story and see if somebody could get me in the right direction in order to solve it, any comment or suggestion would be appreciated.

This is a Mercruiser 502 MPI, gen VI,its got a cam, ported ,and headers, gives around 450 to 500 hp, the hull is a 24 foot Donzi Spirit, its a 60 -65 mph boat. I did not winterized my engine, I was new to boating and even newer to winterizing an engine. So, went to my storage unit one day, and saw two freeze plugs in the bilge, and thought to myself "great!, they did their job!", went to the autoparts store, got two expansion plugs and put the boat in the water, started the engine, took off, and noticed it did not rev above 2700 - 2800 rpm at wot. Stopped, shut in down, check the oil and boom! ..oreo milkshake. Thought to myself that water in the engine prevented it from accelerating. Got a new block, had the heads checked ok, and "transfered" everything to the new block, and still, engine does not rev past 2800. Sent ECM to have it checked, no issues with it. Replaced injectors, checked wires, checked power to injectors, compression, fuel pressure, filters, and the issue persist. Im not a pro teck, just mecanically inclined, and dont know what else to check, any suggestions?? Thank you all.

Does this mean you got just the block and installed your old cam, or new block came with fully assembled less heads (long block)?

Who built the motor, you or someone else?

The ice broke somethings.

freeze plugs is bad terminology. They are actually casting plugs. But yeh, they can be pushed out from ice, thus prob why they got nicknamed freeze plugs. Sorry for your loss.

Might want to check your wallet, things might get expensive. :party-smiley-004:

I just got a new bare block, same pistons, crankshaft, rods, heads (tested ok) and cam. Machine shop build the short block and I did the rest. Engine starts, sounds healthy but the issue persist. Thanks

Thats right, casting plugs. Thank you SB

haha ...I hear you man :cool:

A machine shop build the short block, crank, pistons, rods and I installed the heads, cam and the rest. Same issue as the day I found out about the block been cracked. Thanks

When you but it back together did you put the ecu in base timing mode to adjust the timing ?

Did they use your old cam or a new one?

Your old one good then this is one less thing to think about

If it was new cam or one from another motor need to know if it was same profile

Are you sure it's a 502 block and not a 454, (checked numbers)?

Just spit balling

Base timing mode?? ...I did not, but I took the boat to this guy`s shop, he said he set it in time, replaced the IAC, but did not fix the issue, he thought he did

Hi there, yes I made sure it is a 502 block, guys at the machine shop also made sure it is a 502. I installed the same cam. The issue came on before I took the engine apart, ice related or not, I dont know. Thanks

haha tell me about it!

That engine ( mefi 3 ecm ) needs to be set in base timing mode with ether a hand held scanner or lap top with software in order to set the timing, you need to follow up with your guy, if he's not a marine guy he might not know this.

All MEFI s can be placed in base timing more with a paper clip placed on the DLC connector

Check the intake. If it was a saltwater engine.