1964 Evinrude Sportwin 9.5 HP slows then surges, then slows and surges, then dies?

[DarylL]

This little outboard has been very dependable for me for about 5 years. It is on a 14' john boat and I use it in the Neuse River in NC year round for fishing and duck hunting in the winter. One time the carburetor needed cleaning and the fuel lines needed replaced. A few days ago while heading back to my dock at WOT the engine slowed way down from max RPM to about half speed then slowly back up to max RPM then slowed again. It did this for about the 5 minutes it took me to get to my dock. I cleaned the carburetor and put it back together then it really acted fussy. So I cleaned it all again. I changed the inline filter and cleaned the fuel pump. I changed the primer bulb and fuel lines. I noticed little pieces of yellowish gel in the gas line components. I've cleaned and blew out everything in the fuel system. I changed the spark plugs and cleaned and checked the points. It still seems to do the same thing going up and down in RPM. If I run it with the choke on it seems to help for a while then it will start doing the same thing within about a minute. I also have been noticing small fuel bubbles coming to the surface of the water behind the engine. I checked the compression and both cylinders were 65psi with the engine cold. If anyone has any ideas I should would appreciate it.
Daryl

 

[racerone]

Try running with a different fuel tank as a test.-----Possible air leak at the fuel connecter.

 

[geoffwga1]

Check that it's not suffocating from an exhaust leak inside the cowl,these 9.5 motors are notorious for it.The usual culprit is the short convoluted hose that runs from the exhaust casing out through the lower pan.I too have 64 version and a 63 and they have both done it at odd times.The part # is 309830 but it's listed as unavailable so you may have to make something up if that turns out to be the problem.

 

[SolingSailor]

Float / valve in carburetor?

 

[DarylL]

racerone- I have not tried a different fuel tank yet. I guess I didn't say this before when I changed the primer bulb I changed the whole fuel line from tank to engine including the hose connectors. It was all one piece. I have a clear inline fuel filter under the cowling and it is full of fuel. There is definitely fuel in the bowl because I can unscrew the drain and it comes pouring out.

geoffwga1- That is what I was thinking after reading some other threads. I looked at that exhaust hose and it looks solid. I also tried running the engine without the cowling and it preformed exactly the same way.

Solingsailor- I cleaned the float valve well and I can move the float up and down and it seems to work properly. I put it all back together I obviously can't see in the carb to make sure it's working well when it's assembled but there is fuel in the bowl and it doesn't come out of the overflow so I'm assuming it's working properly.

I really appreciate the ideas please keep them coming.
This gas I'm using is fresh non-ethanol and I'm using the same 2cycle oil I've always used. I'm going to get some premium gas which has ethanol in it and see if that makes any strange difference.

 

[racerone]

Then check inside the fuel tank for a leak on the pick up tube.---Known to be a problem on plastic tanks.----Is it a gradual surging or an instant change in power ?-----Have you checked for bad ignition coils.----Most of these motors I own ( about 10 of the 9.5 ) either have 2 new coils or they need 2 new ones.

 

[Rick.]

Try pumping the bulb when the motor is running poorly. Best of luck. Rick.

 

[DarylL]

racerone- I will check the tank. It seems to be getting the fuel without a problem. The inline filter is glass and I can see it stays full. The bowl seems to be staying full as well. I had the flywheel off last night and everything under it looked like new. I cleaned the points and checked the gap. I polished the inside of the flywheel with a little 800 grit wet sandpaper and that's nice and shinny.
How do I check the ignition coils? I checked the spark plugs and I'm getting consistent spark?

Rick- I'll pump it and see if that help.

Thanks everyone!

 

[racerone]

Not sure why one would need to shine the inside of a fywheel ??-----Does spark jump an actual gap of 1/4" or more ?-Have you checked for cracked plug wires where the have a sharp bend coming out of the magplate ?

 

[Rick.]

Not sure why one would need to shine the inside of a fywheel ??-----Does spark jump an actual gap of 1/4" or more ?-Have you checked for cracked plug wires where the have a sharp bend coming out of the magplate ?

LOL. That's the type of thing I do when I'm stumped and thinking about what to try next. Rick.

 

[DarylL]

Rick- I pumped it a little while it was running, mainly when it was about to stall out. It seemed to help. You are right about polishing the inside of the fly wheel. Stumped and thinking about what to do next. Plus there was a ring of crud around the inside. I thought it might be some metal shavings ground onto those magnets in the flywheel and interfering with the timing. Either way I like to clean things good before putting them back together.

racerone- It was a gradual surge as you asked previously I think you were trying to determine if it's a fuel or ignition problem. If I'm smelling what your stepping in.
I assumed fuel after thinking about your question. I opened the fuel tank and there was a crack in the tube. I bought a new fuel tank and put new fuel in it. It started right up and ran no problems!

I was just running it in my drive way.

I'm going to put it in the water this afternoon and will let you know how she does. Thank you for your help!
Daryl

 

[Rick.]

Well it sounds like your onto something. I clean while I contemplate. That's why many of my motors are so clean. Please let us know how if the new tank made the difference. Sounds like it will. Rick.

 

[racerone]

Newbie owners are often reluctant to take advice from someone with over 40 years of repair experience.---Not stepping in anything here just offering top notch advice for no $ at all.-Hardly any thanks too.

 

[DarylL]

Thank you very much Racerone and Rick I used my boat the last two days without any problems! I'm thinking it was that crack in the tank tube that was causing the problem. It's running perfectly I'd still be scratching my head without you're help.
Thanks again
Daryl

 

[Rick.]

Well that's good news. Racerone nailed it in his first and second post. This forum is such a great place for us all to learn. Rick.