1978 90 HP Merc stalls out at full throttle

[Bchappy]

I ran 8 tanks of gas through it this spring-fuel bulb occasionally collapsed and had to pump it it to keep from completely stalling out.<br />Since then newplugs,pulled carb bowl fittings and drained/got new fuel/ and now here I am____<br />-at half speed it runs but I have to keep jockeying the throttle to maintain a constant speed<br />-at full throttle it runs for a minute or so then stops dead . It restarts easily runs for a minute at full throttle then stalls again -motor has a strong pee but it takes 15 seconds at a higher rev to get it to begin to come out.<br />-

 

[Elmer Fudge]

Re: 1978 90 HP Merc stalls out at full throttle

Bchappy <br />Cadet <br />Member # 59289 <br /><br /> posted June 13, 2005 03:02 PM <br />--------------------------------------------------------------------------------<br />I ran 8 tanks of gas through it this spring-fuel bulb occasionally collapsed and had to pump it it to keep from completely stalling out.<br /> <br /><br />---------------------------------------------------------<br /><br />Check that your fueltank is properly venting.

 

[cistn]

Re: 1978 90 HP Merc stalls out at full throttle

my 30 hp 4 stroke did the same it was the STATOR, ASsoon as it was replaced the problem went away,<br />they cost about 250.00 but still chaeper and you can do it youself in about 1 hr. good luck

 

[laker925]

Re: 1978 90 HP Merc stalls out at full throttle

what do you check exactly to see that it is venting properly?

 

[MortenH]

Re: 1978 90 HP Merc stalls out at full throttle

Check fuelpump, fueltank venting, fuel-lines, new fuel bulb, etc. Sounds like fule problem to me.<br /><br />-M-

 

[macshak]

Re: 1978 90 HP Merc stalls out at full throttle

I have a 78 Merc 900 90hp and have simular problems. Seems to be fine until I switch to the second tank. Then I have problems with it cutting out, usually about the time the skier is half way out of the water. Have played around with the vent cap, but doesn't seem to help any. In process of replacing entire fuel line. That is, after I replace the floor and stringers. What fun!

 

[Bchappy]

Re: 1978 90 HP Merc stalls out at full throttle

Thanks for the feedback I just pulled the battery and found low water and "0" charge left.<br />Would this be an additional indicator?

 

[laker925]

Re: 1978 90 HP Merc stalls out at full throttle

How do you check the venting,and the fuel pick up,spoken abot earlier?

 

[macshak]

Re: 1978 90 HP Merc stalls out at full throttle

My fuel tanks have a vent on the cap that you can tighten and loosen. I am also installing a clear fuel filter inline so that I can watch the fuel flow.

 

[laker925]

Re: 1978 90 HP Merc stalls out at full throttle

Ouch!those glass ones?! threw mine in the trash! Can cause trouble (so the boat rebuilders tell me)with fuel starvation .And especially if between the bulb and the motor.I had a repair man try and move it from before the bulb to after(starving the motor) -for better business for the repair guys!<br />I've installed a cannister filter/water seperator in mine-much safer and it wil seperate any "humid" water that may build up in a tank,and I put it before the bulb!<br />Good luck!

 

[macshak]

Re: 1978 90 HP Merc stalls out at full throttle

laker, thanks for the warning. I am still rebuilding the floor/stringer. So when I get around to it, I will check on a cannister filter.