Full throttle surge

[Skeezix]

Well we got the old (1977) 70hp on the water today and it ran pretty well. Seems to run ok up to about 3/4 throttle, any more than that and it starts to surge. Ball isn't totally hard but isn't totally soft either. I was thinking either fuel pump, ball or maybe both. It's pushes a 1978 Starcraft 18' ss up to 36 mph and then starts to surge. Hard to believe it is hitting a rev limiter with that small a motor on that big of a boat. Anybody have any thoughts they would like to share? Thanks

 

[phillnjack2]

Re: Full throttle surge

sounds like bad fuel pump or more than likely dirty carbs.
could be a bit of crud in the carbs from inside the fuel pipes if they are getting a bit old !!!

does it also do it if you pump the ball at higher rpms ?

phill

 

[Skeezix]

Re: Full throttle surge

Yes, doesn't Seem to make a difference.

 

[Daviet]

Re: Full throttle surge

I would pull the high speed orifices and see if they are restricted or plugged, if so pull the carbs and clean them properly.

 

[Skeezix]

Re: Full throttle surge

I would pull the high speed orifices and see if they are restricted or plugged, if so pull the carbs and clean them properly.

Sounds good, thanks for the input. Will give it a shot and see where it takes me. Thanks to everyone!

 

[Daviet]

Re: Full throttle surge

Let us know it turns out.

 

[Skeezix]

Rebuild kits have been ordered and am reading manual to prepare for the task. I ran it with the air box off and could see gas pouring out of the # 2 carb throat. Iam guessing that the float is saturated as a few solid raps on float bowl didn't seem to help. Could this contribute to high speed surge or would this create an issue thru the entire rev range. Thoughts?