Hey all:
1985 GT150
Model: J150STLCOH
Serial:J6131805
Main symptoms: Excessive white smoke. slight sneeze at idle, bogs (with surging) starting at 5,200rpm.
Compression is on the lower end of the scale - but was even until this year. The symptoms have not changed from last year, so I don't think compression is the cause.
Starts like a champ. Idle is ~800rpm in the water, in gear, at idle throttle.
Smokes like a heck when started and when idling first off. If you come off a run at 5,000rpm, it smoke at all while idling into the marina.
Sometimes, after idling, it won't get rpms up to get on plane - (it will rev in neutral, and haven't tried choking it yet). It will eventually "clear" and run great up to ~5,200rpm.
It bogs after 5200rpm - MOST of the time. Occasionally, it will "catch" and fly to 5500rpm. It sounds like fuel starvation and it surges some in that range - so I don't really try to run up there - but it also makes me wary of timing.
In general, low end and Mid-range response is phenomenal.. torque for days.
The bulb: replaced last year - did not clear symptoms up. I can pump it up hard, but it always, always lets me pump just a tiny bit 1 more time... each time I hear the tiny bit of fuel going somewhere, but I don't see it at any fuel line connections. [all fuel line from the tank to the engine has been replaced] I replaced the fuel pump last year with the recommended pump from MasterTech Marine. - fuel is mixed 50:1 in the tank (was that way before I bought it 4 years ago)
Carbs: Carbs were rebuilt last year at a shop. Full kit was given to the mech. I hope he used it all. After he finished, it had the same symptom as before - in that it smoked and started to bog at 5200rpm (it surges a bit).
I de-carbed again yesterday, and changed the fuel filter.
I have an original repair manual that should be here this weekend. I have leak-down gauge, fuel pressure gauge, and carb sync gauges available.
I have (2) check valves on the way (all 6 could be bad for all I know) - but looking at it, it looks like I need to order carb gaskets and pull the throttle bodies to get to all of the check valves.
thankful for any help or guidance. - all ears