1978 35hp fuel problems

[Doubles Shooter]

I have a 1978 35 horse. 35EL78R. I had to replace the fuel pump this spring. I put in a new OEM pump. Barrel tested it and it ran great. Took it to the lake and. It ran perfectly for a 6 mile run to our fishing spot. Fished for a few hours with the electric. When we left, the motor started up instantly. When I hit about 3500 rpm, it cut out. It would only run with the choke pushed in. Primer bulb pumps up and is firm when it acts up. Got it home and back in the barrel. I put new connectors on the fuel line. Line and bulb were new last season. Again ran great in the barrel. I had it in gear and ran it with a load till the water blew out of the barrel. Refilled it twice. Motor ran great. Back to the lake only to have it cut out in a quarter mile.
Don't know why it ran so good then terrible. Where to start? If it is a clogged high speed jet, why does it run great at times then nothing?

 

[racerone]

Clean the carburetor. -----Test run with another tank.

 

[Doubles Shooter]

Thanks, Yes. I was afraid of that. I just don't want to change any adjustments on the carb
It runs too good. I can troll 900-1000 rpm for hours without it loading up, then hit the throttle and off she goes.
Oh well, off for the tools.

 

[jimmbo]

The only adjustments will the Float, the Sync between the Timing and the Carb, and the Idle Mixture and Speed, all very easy on that engine.

When it dies, does it start up again easy, or does it take forever?

Motors quite often run fine in the barrel, simply because they are not under any load, it takes very little air and fuel to hit 6 grand in neutral, but on a boat at the lake it is a different story

 

[Doubles Shooter]

Thanks, Jimmbo. For being 44 years old, it purrs like a kitten.I might dig into it tomorrow. Spent the weekend at camp. There must be something loose floating around in there. I had the wife and two small grandkids last week. I have a Starcraft tinny. Motor ran like a champ for half an hour riding around. Fished a couple hours and headed back to the launch. It ran great for a couple hundred yards then got goofy.
I'm going to try to drain the float bowl into a white cloth to see if I catch anything.
Can't wait to find what's going on.

 

[440roadrunner]

Could be several things in no order
1...Defective pump
2...More likely dirt/ debri which was knocked loose when you replaced pump
3....Crack in hose/ loose fitting admitting air on suction side

I would forget "don't want to touch." The big two things affecting your adjustment is "if" the carb has some gum, which means the settings will change when cleaned, and of course float level and the idle mixture screw setting

So "gingerly" and carefully screw in the idle mixture, carefully counting the turns and write that down, then just re-set that when done

I would go through the fuel system stem to stern. Replace ANY suspect hose and certainly the hose in the engine itself. Blow out all fittings, I would also disassemble the pump, looking for dirt/ debri. Obviously replace or install a good filter. I would tear the tank hose apart, blow it out, inspect, and replace any suspect hose.

IT IS MY BELIEF that this alcoholized fuel deteriorates some hose pretty badly and sometimes quickly

 

[Doubles Shooter]

Got time to attack the carb. Clean as a whistle inside. The thing I found was a float valve needle I have never seen before. It appears to have a rubber tip. When I pulled it out, it had a point, but was black. I thought it was crud built up on it till I wiped it off and the end rubber off and the end came off it. I'm thinking it was hanging up in the seat. There was no clip to pull the needle down with the float. Just gravity to open it. I put in the replacement seat and needle. Motor runs great in the barrel, but I won't know for sure untill I lake test it.

 

[jimmbo]

A lot of the Inlet Valves have a Neoprene tipped Needle. Just be careful when setting the Float, as the Neoprene can flex a bit, resulting in an incorrect float setting, and the Neoprene can be damaged.
Did you remove #5, a lot of junk can accumulate there and you can soak the carb for days and it doesn't get rid of it.
Once you put the carb back on, you have to do a Link and Sync to verify the Synchronization between the Carb and Timing are still as spec, and that the Carb fully opens at full throttle

 

[Doubles Shooter]

I finally got a chance to hit the lake today. The boat ran great for me. Burned most of a tank of gas running at idle/trolling speed to wide open at 5400rpm, and everything in between.
I did pull the freeze plugs from the carb, soaked and blew out everything. I figured as long as I had to pull the starter to get at the carb, might as well do it all. Thanks to everyone for your time. We're back in business.

 

[440roadrunner]

Very good! "Endeavor to persevere"