140HP mercruiser inboard surging at high revs

[dalcan]

Hey guys ,

This is my first post so hopefully i'm in the right place. I have a 1975 StarCraft Holiday with a 140HP inboard engine that as the title states is surging at max revs but otherwise runs great. I've replaced the fuel lines, installed a new fuel filter ,had the carb cleaned, replaced the fuel pump, drained the tanks and ran new gas. Would there be a restriction in the 3 way fuel valve as its the only thing I haven't changed yet. Thanks for any help.

 

[dozerII]

Re: 140HP mercruiser inboard surging at high revs

If you have a portable gas tank, try running off that straight to the fuel pump. That will tell you is it is in the tanks or lines.

 

[Grub54891]

Re: 140HP mercruiser inboard surging at high revs

Carb cleaned to some means spraying carb cleaner in it and around it. Was it dissasembled/new kit installed? It'll never be right if it was not done right. At least it would eliminate the carb if done with a kit.
Grub

 

[dalcan]

Re: 140HP mercruiser inboard surging at high revs

Carb cleaned to some means spraying carb cleaner in it and around it. Was it dissasembled/new kit installed? It'll never be right if it was not done right. At least it would eliminate the carb if done with a kit.
Grub

The carb was taken apart and cleaned by a mechanic.

 

[dalcan]

Re: 140HP mercruiser inboard surging at high revs

If you have a portable gas tank, try running off that straight to the fuel pump. That will tell you is it is in the tanks or lines.

Thanks i'll give that a try. I was also told that some of the fittings into the 3 way valve have small ball bearing check valves in them and should be replaced with straight thru connections to reduce restriction or at least cleaned , I will check that too.

 

[TheHunter990]

Re: 140HP mercruiser inboard surging at high revs

Another thing to check, if you have access to a timing light, is that you have a steady timing at max rpms. You could have a worn out distributor that could cause surging if the timing is fluctuating. You might need to check it on the lake rather than at home with the muffs on it.