1980 25hp Evin planes out then dies

[brim_buster]

So for the last 2 weeks after rebuilding the carb thinking that was the problem and buying a new gas tank, this motor will plane out and then die flat on its face. It wont fire right back up and if it does all I can do is putt around. If I go to give it gas it will die. Then its a bear to get started. I dont think its a fuel or carb issue I think something is getting hot and shutting it down. Any one have any ideas. Thanks in advance

 

[jimmbo]

When it acts up, does it still have spark? It still sounds like a fuel issue. Does the primer bulb collapse? Is the fuel filter clean? What condition are the fuel lines, internally. Fuel pump and pulse hose(if the pump isn't mounted on the transfer cover) Have you tried spraying some gas-oil into the carb when it refuses to start?

 

[brim_buster]

I havent checked spark but it acts like no spark. Filter is clean, primer ball is good. New fuel pump.You see plenty of fuel in the filter.fuel lines are good. But it will spin over till the starter gets hot and nothing. Sometimes it will fire up and putt along all day with me shutting it down and firing it back up. But when I hit it full throttle and it gets to plane it just dies. The carb is pristine will everything new in it.Almost acts like an old chevy with the control mod in the distributor going bad.You let it sit awhile and it will run. If it sits over night and you go out it runs great and planes out and dies then it wont do squat the rest of the day. Dumped out a half a tank of gas thinking water in fuel.

 

[jimmbo]

"I havent checked spark but it acts like no spark." Well check for a good healthly spark. I think the test spec is for a 5/16" or 3/8" gap. You might have a heat issue. It only does the 'Die and won't restart' after a burst of full throttle, but it will idle all day and restart without issue?
If there was water in the tank, and you dumped 1/2 the tank out, there is still water in the tank as it would have been at the bottom and would not have come out.

 

[brim_buster]

no I had a half tank of fuel and dumped it, but then we went to wally world and got new tank and fresh gas. If I take it to the river and run it and it does the same thing and no spark what should I look at replacing? Or what should I be testing to eliminate the issue

 

[brim_buster]

The wife wont get in the boat till I fix the problem.....LOL

 

[jasper60103]

Your symptoms sound very similar to what I experienced on my 1981 Johnson 25hp.
It would only act up at the lake (not in a tank), so troubleshooting was frustrating and inconvenient.
I tried a different gas tank, fuel line, new carb kit and power pack with no success.
I've since moved on to another motor, and that one has been sitting in the garage for several years now.
I'm looking forward to hear what you discover. Please keep us posted.

 

[Tim Frank]

Four steps to effective troubleshooting and minimising wasted effort:
1) Beg, borrow, or buy an OEM repair manual for that motor.
2) Check compression
3) Check spark with purpose-built tester.
4) Check fuel pump suction and output pressure. Model specific values and procedure will be in manual from 1.

By this point you will have a very good idea where the trouble lies (or equally useful, where it does NOT lie) and have spent no money or time chasing a "gut feeling".

 

[211libwtfo]

This is about the only thing I ever say. ANTI SIPHON VALVE. I think it’s overlooked sooo many times.

 

[racerone]

Put a timing light on it and see if you are loosing spark to one cylinder.----Does spark jump a gap of 7/16" , yes or no ?

 

[brim_buster]

Four steps to effective troubleshooting and minimising wasted effort:
1) Beg, borrow, or buy an OEM repair manual for that motor.
2) Check compression
3) Check spark with purpose-built tester.
4) Check fuel pump suction and output pressure. Model specific values and procedure will be in manual from 1.

By this point you will have a very good idea where the trouble lies (or equally useful, where it does NOT lie) and have spent no money or time chasing a "gut feeling".

I have a manual, 120 psi on both cylinders and pretty blue spark when running good. Dont know what an anti siphon valve is. havent checked fuel pump because its brand new and OEM replacement like all the parts I buy. It was running great till 2 weeks ago. I guess I will have to run it in the river and when it dies I will go to a sand bar and start checking spark etc. The plugs are champion gapped at 40 and new and clean.

 

[racerone]

Crankcase compression drives the fuel pump.----There may be issues with that.----Maybe pull the flywheel and have a look at the bits there.----Perhaps an issue with wires that are broken inside the insulation.

 

[Saintnowhere]

could be one of the following, a flooding issue , tank not venting properly , fuel pump leaking or coils are cracked. possibly plug wire issue at wot either causing missfire due to rub through or stretching also the kill switch wires could be bad. also check all fuel lines for cracks.

 

[brim_buster]

Crankcase compression drives the fuel pump.----There may be issues with that.----Maybe pull the flywheel and have a look at the bits there.----Perhaps an issue with wires that are broken inside the insulation.

But it has 120lbs compression with new pump. And inline filter stays full. I will continue the daunting task of narrowing it down by checking everything mentioned and will get back with results. Thanx for all the help.

 

[racerone]

But compression in the cylinders has nothing to do with compression in the crankcase !----Up to you to trouble shoot.

 

[Tim Frank]

Is there a spec/procedure that one can use to check crankcase compression?

 

[Tim Frank]

"I have a manual, 120 psi on both cylinders and pretty blue spark when running good. "

How did you check spark?

 

[brim_buster]

But compression in the cylinders has nothing to do with compression in the crankcase !----Up to you to trouble shoot.

should I put a guage on the fuel pump to check pressure from the pump? Ive never had to check crank case pressure before.

 

[Silvertip]

It isn't just crankcase compression. The crankcase undergoes pressure/vacuum cycles. Vacuum draws fuel into the crankcase and when the ports close, pressure forces the fuel to the combustion chamber and scavenges the exhaust. Is the primer bulb being sucked flat when the engine dies? If so, there is a restriction in the fuel system between the bulb and the pickup in the tank. Have you tried squeezing the primer bulb when the engine begins to bog? If that momentarily helps the engine pick up a bit, you probably have a bad fuel pump. What do the plugs look like? Wet, dry, tan, white, oily?

 

[brim_buster]

It isn't just crankcase compression. The crankcase undergoes pressure/vacuum cycles. Vacuum draws fuel into the crankcase and when the ports close, pressure forces the fuel to the combustion chamber and scavenges the exhaust. Is the primer bulb being sucked flat when the engine dies? If so, there is a restriction in the fuel system between the bulb and the pickup in the tank. Have you tried squeezing the primer bulb when the engine begins to bog? If that momentarily helps the engine pick up a bit, you probably have a bad fuel pump. What do the plugs look like? Wet, dry, tan, white, oily?

primer ball is good. Plugs are clean, and the wife pumped the primer when it went to die and it didnt do anything.I used real fuel line and it has a Sierra primer ball that doesnt go flat and works like it should.
I just need to check for spark when it dies which I havent done yet