Topic: 65 Sportwin surging at high speed – Antique Outboard Motor Club,Inc

This topic has 57 replies, 13 voices, and was last updated 9 years, 5 months ago by willg.

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May 17, 2015 at 5:33 pm #1517
willg
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Well I have an issue with my new to me 65 9.5 Sportwin I picked up recently. It’s surging at high speed. It seems like it wants to go but just can’t. It will plane my 14 foot Lowe no problem but loses rpms and then gains them back and repeats it over and over. It does not seem to be fuel related as I had the carb apart and it’s spotless inside. Running it with the cover off does not change how it runs whatsoever. Squeezing the primer ball has no effect as well. I took the flywheel off and noticed that BOTH sets of points are set less than 0.020", could this be causing my issue? The oiler wick is completely disintegrated so I am planning on rebuilding the mag plate with new coils, points, condensers, and wires. Compression is 70 psi on both cylinders.
May 17, 2015 at 7:17 pm #16235
frankr
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US Member
I suppose you need to decide whether it is fuel or ignition. Easy for me to say, huh? I know that you know what you are doing, and should be able to tell the difference. Of course, points could be the problem if off far enough. How about the spark plugs–high speed miss??
May 17, 2015 at 7:22 pm #16236
willg
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US Member
Plugs are new Champion J6C’s, not dropping a cylinder, just loosing RPM’s then gaining it back. I guess I could always clean and reset the points and go for another ride and see what happens. When I got this motor, I did nothing to it at all, except for impeller and t-stat. Found the issue after running it on the boat for the first time yesterday at the Thompson CT wet meet. I don’t think it’s fuel as playing with the choke has no effect as well.
May 17, 2015 at 7:30 pm #16238
jpatti75
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I’m know you said that you primed the bulb to no effect, but I’d still give the fuel pump a once over. From your description, that is the first thing that came to my mind.

JP
May 17, 2015 at 7:56 pm #16240
willg
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I cleaned and reset the points to 0.020", and reinstalled the flywheel. Going to try and take a ride tomorrow night after work.
May 18, 2015 at 1:44 am #16275
brook-n
Participant
Could you have a gasket that is going bad causing you to loose crankcase compression?
Or a bad seal on the carb base gasket?

Just a thought.

Respectfully
Brook N.
May 18, 2015 at 1:46 am #16276
willg
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US Member
Brook, on this motor, the crankcase is sealed with an anaerobic sealer and the carb base gasket is new. When I had the flywheel off the area around the crank seal was dry.
May 18, 2015 at 2:04 am #16282
brook-n
Participant
Just figured I would put it out there, I had a similar situation and it ended up being a gasket
Seal.

Respectfully
Brook N.
May 18, 2015 at 11:28 pm #16386
willg
Participant
US Member
Ran it again after work today after resetting and cleaning the points. Still a no go with running at high speed 🙁 . Talked with the guys at work and one of them suggested it could be the pump not supplying enough fuel at WOT. Swapped the pump off of my dad’s 91 Evinrude 15 (the small square pump) and will try running it again.
May 18, 2015 at 11:42 pm #16389
Mumbles
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It could be one of the capacitors going away. Just because they’re new doesn’t mean they are good. Since I’ve had several Champion plugs fail right out of the box to, I stick with NGK’s now.
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65 Sportwin surging at high speed

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