1990 merc EFI 200 sporadic power

[sacandagaric]

This outboard was fine till this year. Now, starts OK, idles fair, no power for hole shot. WAter in fuel filter, Replaced it. Plugs were fouling, cleaned em, ran fine for hour, then not (fouled). Replaced em. Compression touches 120 on all 6. EFI, and I use the oil injector (not disconnected). Suspected gas quality but have run two refills. Always 93 Octane. Temp runs fine. After one hour on the new plugs, same problem. It struggles with the hole shot but if it does get on plane, opens up hits 5200RPM and 62MPH+ which is close to max performance.

Seebold 21 ft, 28p three blade.

Why does this happen?

 

[sacandagaric]

Re: 1990 merc EFI 200 sporadic power - too much oil?

Re: 1990 merc EFI 200 sporadic power - too much oil?

It may be bad etiquette to reply to my own post, but i am really hoping some of the experts here can help! My own thoughts further ....

Since performance varies I think it is NOT the EFI unit. Safe conclusion?

I know people often disconnet the oil injector and go back to custom mixing, probably fear of under-oiling. I dislike this approach, because the injector uses different mixes at different RPM, mixing in the tank can't mimic that.

I wonder though, is it possible my oil injector is over-oiling? Maybe an oil injector is stuck open somehow? The oil tank is pretty big (2-3gal?) so I can't judge oil consumption. She does smoke a bit, even for a merc. I'm thinking of disconnecting the oil injection and mixing in the tank (uggh) to see if performance doesn't hold up better.

Can I get a refresher on proper way to disable the oil injector?