Mercruiser 120 bogging down and dying at wot

[powell0819]

This is my first post here. After reading alot of posts I have decided to give a shot at letting you all try to help me and my husband get this figured out!!

We have a 76 sea sprite with a 120 hp mercruiser that we just bought. The previous owner had it running and everything on muffs and we didn't notice a problem until we took it out onto the water.

When we give it throttle it does fine, but only at a small amount of throttle. When we give it throttle to the point where the nose starts to come up it boggs down and dies. We thought it might of just had a dirty carb so we sprayed carb cleaner in it while it started to bogg down. It immediately gained power at that point and leveled out and went to wot with no problem. So we let her go to idle and tried it again. This time it bogged down yet again and died when we gave it a good amount of throttle.

If we adjust the carb screws (rochester 2gc) when it is bogging down we can get it up to wot without using the spray but if we try to idle down at that point it of couse dies at idle at that point.

We have thought it might be fuel lines, fuel filter or maybe the carb needs rebuilt? We went ahead and ordered the rebuild kit so we can work on it when we get off the road in a week. Do you think that our speculations are correct in what might be wrong with it or do you think it could be something else? Im hoping its not the fuel pump those are expensive...

Please lend us your merc knowledge... We need help with this one Thanks!!!

 

[Infinite Monkeys]

Re: Mercruiser 120 bogging down and dying at wot

Hi,

Seems to be a carb. issue. My old VW use to do that as well. I rebuilt the carb but did not help. It turns out it was the cross shaft bushing that was worn out and needed to be replaced. Worn bushing was letting in too much air. It worked great after I did that.

 

[jherlyn]

Re: Mercruiser 120 bogging down and dying at wot

Could be fuel lines. I had to do something similar on a mercury outboard. It would get up and go, but when it got close to WOT, it would bog down and die. turns out one of the fuel line connections had worn out and it was sucking just enough air through the connection that at WOT it would starve out.

 

[Fordiesel69]

Re: Mercruiser 120 bogging down and dying at wot

Work from the tank to the carb, never the other way. Now that you have....., try this: Remove inlet line from fuel pump, connect a new line to it and run it into a full 5 gal gas can. Drive again, if solved, you have a fuel pickup problem. If not you have a fuel pump / carb issue. Although being unknown it sure can;t hurt to rebuild the carb.

 

[powell0819]

Re: Mercruiser 120 bogging down and dying at wot

Wow thanks everyone for the speedy responses! When we get home this week I will post and let you all know what ends up fixing it. Im hoping its easy and we will take it one step at a time so we know for sure what it ends up being.

 

[powell0819]

Re: Mercruiser 120 bogging down and dying at wot

Since I never had responded to tell you guys what the fix was, I figured I would just incase someone looks at this because there boat is doing the same thing. And *cough* sorry for replying to an old thread but I felt bad for never saying what happened to our boat! :facepalm:

We started with fuel lines. No fix even though fuel lines were corroded very badly. Then replaced fuel pump. That didnt help either. So we rebuilt the carb. The accelerator pump was sticking and we had to get a couple different kits for some reason because we couldnt get the accelerator pumps to work right. That helped somewhat but didnt complete the fix. The distributor cap had some stuff not right in it so after having an older boat guru help us out on it the boat ran perfect! We still have a hiccup with the shift interupt but other than that, she purrs like a kitten. If you are reading this and have a similar issue and want some advice from what we did to ours, feel free to let me know and we will help with what we can!