Bogs down under load.

[Scoot1987]

Have a 1977 Mercury 9.8 that runs great in a drum of water. Get it out in open water and rpms will not increase and bogs down. I have gone through the carb, fuel pump and all new few lines. I am scratching my head. Any info will help.

 

[racerone]

Post the actual compression test values.----And does spark jump a gap of 3/8" on both leads.----Sounds like it might be running on 1 cylinder.----Could be a bad reed valve as well.

 

[Scoot1987]

Post the actual compression test values.----And does spark jump a gap of 3/8" on both leads.----Sounds like it might be running on 1 cylinder.----Could be a bad reed valve as well.

Thanks, will check and get results.

 

[Scoot1987]

Have 105 psi on both cylinders, and good spark going to both plugs.

 

[Scoot1987]

Took the boat out today. It seems to be a fuel/fuel delivery issue. At full throttle I achieved a whopping 4mph. When I would mist starter fluid in front of carb I achieved 13-14 mph. Now I have to determine if it is a fuel pump carb or vacuum issue..

 

[Scoot1987]

Does anyone have a good diagram or can explain the gasket order for the carb and fuel pump for my 1977 9.8 hp outboard

 

[racerone]

Is there a rubber diaphragm and an identical plastic one ?

 

[Scoot1987]

Is there a rubber diaphragm and an identical plastic one ?

Just a rubber diaphragm

 

[racerone]

Perhaps there is an issue with crankcase compression.----Crankcase compression drives the fuel pump.----Upper and lower crankshaft seals bad?--Labarynth seal bad ?--- -Reed valve bad?----Or combination of both of these.