Mercury 70 engine bog/ loss of power

[Nautique93]

starts and idles fine, will run wot for a few minutes then lose power all the way down to idle, and will stall unless you take it out of gear. when it stalls it will start straight back up, will rev in neutral, idle in gear but give it some revs and it bogs down. seems like it happens once the engine warms up. the engine has good compression- 135 psi on each cyl. I have tried squeezing the primer bulb while the engine is bogging and it makes no differnece- although after squeezing it once it stays squeezed until you come off the throttle- so i assume the pump is sucking enough? The engine is a blueband early 80's 70 HP

 

[Laddies]

Re: Mercury 70 engine bog/ loss of power

Your problem could be a couple different things, heat from the imp or a sticking popit valve if so equipped thats bad, I can't tell from here with out a serial number or a lean mix from a partially plugged high speed jet.

 

[Nautique93]

Re: Mercury 70 engine bog/ loss of power

S/N is 9353189. i am in the UK and havent managed to find this serial on any of the lists. The engine doesnt seem to get hot- it has a good stream of water that is slightly warm to the touch and the temp guage shows about 100 degrees. i have taken the carbs apart and cleaned them- i found little hard black deposits that crumbled to powder between the fingers- not sure what that was- if its any help. ran the engine again and no change.

 

[Nautique93]

Re: Mercury 70 engine bog/ loss of power

im assuming 'imp' means impeller? Also what is a popit valve?