57 evinrude 35hp surging.

[89Aluma]

Hi all just when I get this frankenrude running well it seems to give me more trouble, 57 evinrude 35 power head on a 56 30 hp leg and hood we were cruising on the river around half throttle maybe a little less and it runs great but every once in a while it acts like it's hitting something the motor stutters makes a klack noise once and goes back to running fine I thought it had a 30 hp carb on it so I put one off of another 35 of the same year on it. I've messed with the link and synch thinking it wasn't opening the carb up enough compared to the timing advance basically making a lean sneeze I cleaned the carb thoughouly! Retimed the points again with a multimeter replaced the coils and wires compression is still 120 both cylinders took it back out and really messed with the needles! Got it running god at idle still does the kick back sneeze thing around half throttle but now won't get up to full throttle like it should I played with the high speed while hauling down river leaned it out and it got better but after running for 40 seconds or so at higher rpm it would surge the rpm would suddenly drop and start picking back up it even died one time while this happened took a few cranks to get going again then I unplugged the fuel line and ran the fuel out at the dock and the way it runs when running out of fuel reminded me of how it kicks at half throttle could I be looking at a fuel pump issue? Sorry for the run on sentence lol

 

[oldboat1]

gear case issue? might be a clutch dog, but could be just a linkage adjustment. Maybe the upper and lower shift rods aren't connected properly.

 

[jimmbo]

An engine that sounds like it is routinely hitting things at high speed is often experiencing a worn clutch dog/gears, but since you are having other issues it might not be that.
Sneezing is usually a sign of a lean condition, usually occurs at or just above idle.
Do you still have good spark to both cylinders?

57 was the first year OMC introduced the fuel saving linkage on the big twin. It allowed full timing advance with almost a fully closed carb. Many of those engines and later 40hps had the linkage misadjusted by owners and mechanics who didn't understand how it worked and was adjusted




About 35 yrs ago we had an engine that would run fine one minute, then do the rpm drop, speed up, drop, speed up... We eventually pulled and looked at the plugs. One had a gap that was bridged with what looked like combustion chamber build up. We removed the deposit and the engine ran fine again. Maybe you engine is purging itself of soot and carbon and shorting out the plugs

 

[89Aluma]

The clutch dog is a great idea I hadn't thought of that I'll look at the plugs and see how fouled they are, I've got the link n synch adjustment set so the carb is open a 16th of an inch or so as the line on cam plate passes the needle the needle that comes off the casting. And then I have the full throttle adjustment set so that the carb is fully open with grip at full throttle. I rebuilt the lower unit this spring and never ran the engine before I rebuilt it due to it sitting in my garage all winter, after I bought it, it leaked all the gear oil on the floor for sure gear oil since there was none in the gear case after I had just changed it when I bought it the dogs seamed ok to me I might have a picture somewhere

 

[89Aluma]

No Title

 

[89Aluma]

gear case issue? might be a clutch dog, but could be just a linkage adjustment. Maybe the upper and lower shift rods aren't connected properly.

I changed this to a long shaft to compensate for the 20" transom the shift rod extension was strange to me really thick piece of brass with bigger bolts than the small connector which made it very deficit to get the bolts in I'm wondering if that is my issue I could fabracate one fairly easy I suppose I assume the center of the holes would just have to be 5" inches apart drill a hole for the rods to go into and and then weld a small nut on the back side of the linkage?

 

[oldboat1]

I've used a couple of the brass extensions, but been a while. I don't remember a special issue with them -- think the issues are the same as with the small brass connector. The upper and lower rods have to be fully inserted so the bolt goes through the machined slot in the rod(s). Maybe that's the trouble you had with the bolts (bolts clamping down on the rod, not passing through the slot.) If there is a slot at the bolt hole, you should be able to spread the connector open just a bit with a screwdriver so the shift rod goes fully in place easier. Guessing, of course.

 

[89Aluma]

I'll take a look tonight quick and see if there misaligned I'll report back in the a.m. I'm also going to adjust the the linkage according to the the book page above, I'm going to order a manual for this engine. Any recommendations on which manual to obtain?

 

[oldboat1]

OEM service manual or copy if you can find one (Ken Cook Co., maybe). Look for an original parts manual on Ebay (easier to find) -- often can figure it out from the parts manual.

 

[89Aluma]

Just did the later model shift handle linkage adjustment... it was way off I ordered a clutch dog just in case I need it but I think the adjustment was way off... holding it just barely in gear