502mpi tuning
 

I have a 1994 Stryker with a 502mpi that is not quite right. It currently has about 53 hours since being redone by its previous owner. It doesn't like to idle in gear much....stalls at the worst possible times. It runs smooth enough when I'm up on plane or just running around but it isn't very fast considering what it should be capable of. I figured a 28ft performance boat with a 502 and a 23p mirage plus should run around 58-62mph. The motor has a decent cam and exhaust and sounds great...just not very fast, 52-53mph at 4600??? Are all these issues related? I think somehow there is a relationship somewhere. I am going to change the cap, rotor and plugs this weekend and maybe do some timing and fuel pressure checks. I have a prop going to Darin at Houston prop and I would like to make good use of it....Thanks in advance for any help.

Jason

Re: 502mpi tuning
 

Get your hands on a scan tool. Get it into service mode and check base timing.

Re: 502mpi tuning
 

I concur, of course you don't need a scan tool to kick it into base tiiming. But the tool will give you a guide to associated problems via fault codes if there is anything else funny going on.

Re: 502mpi tuning
 

sounds like a good idea. I will see who has mercruiser service in my area....thanks for the advice. I read another thread that has some idling problems and I might switch to rapid fire #1 plugs. The motor is loading up at idle and stalling out so I pulled the plugs and they do need to be changed to these plugs. Hopefully I'll be able to figure out whats going on in there.