1966 Evinrude 9.5 low power

I was given this engine as part of a trade for the Sea Nymph 12R Blue Water I posted in the boats subforum.

It starts easily and runs well in forward at idle / mid speed. It can be a bit cantankerous to keep running in neutral without advancing the throttle and just seems to have very little power and will only run about 6 mph WOT on the 12 foot Sea Nymph.

I cleaned the carb and blew out a ton of gunk, I believe it was from the cork float deteriorating I resealed it with super glue (did not remove plugs, since a kit was not available locally), checked points / ignition, and compression (60psi on my cheap harbor freight tester but even on both cylinders). I've ordered a proper carb kit, J6c plugs, and am going to decarb it. The only other thing I can think of is a spun prop. The motor was slow at reaching wot which also make me believe I have a carb issue, is there anything else I should check?

A ton of gunk is probably the clue.... If you're sure the float is adjusted and functioning then your likely problem is some gunk in the high speed jet.... If you don't want to disassemble the carb until you get the kit, you can try just screwing the plug out and spraying carb cleaner into the orifice.

When you do the carb kit pay special attention to that area.....

Here's the diagram:

https://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1966&hp=9.5&model=9622A&manufacturer=Evinrude&section=Carburetor+Group

unscrew #77 and flush out that orifice...

Pour a heap of seafoam in the fuel. Helps clean out as it runs.


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I did a bit of research and found out how to check for a spun prop. Sure enough that is at least part of the problem. I can turn the prop with out the flywheel turning. It turned very easily. Didn't even have to put a socket on the flywheel to prevent it from turning.

The drive pin is sheared ? Look at this diagram:

https://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1966&hp=9.5&model=9622A&manufacturer=Evinrude&section=Gearcase+Group

#48 rides in a slot in the back of the prop.... pull the cotter pin and unscrew the hub.... the prop will come right off and you can check it.... a broken drive pin would allow the motor to rev really high, really fast... not slow...

Shear pin was fine. Propeller had worked loose from the rubber core. Got that fixed temporarily with a screw. Decided to go and do a quick run down a local Creek to see if it helped. The motor was a bit difficult to get started,( took about 10 pulls) but when it did it idled well and had even acceleration and a definite increase in speed / thrust. Went about 1 minute and surged then died. I could not get the motor to restart at that point. Checked spark when I got home still going strong, but the plugs fouled so I'm definitely thinking I have a carb issue. Is it okay to spray a decarbing agent directly into the cylinders and pull start a few times to let it soak overnight? I'm assuming it will not be a issue. Also, I realized my enrichment needle is missing a o ring to seal around the threads. I'm definitely assuming that's not helping things. Here's a video showing my prop issue https://youtu.be/Er1qYfWSIf4/

First time I ever saw that... I learned something new today...

Thanks for all the help, I let the engine soak overnight and cranked it over a bunch this morning to clean out the cylinders, a ton of black goo shot out of it and filled up the test bucket, lol. I've also ordered a new fuel pump after discovering that mine had a cracked leg, and ordered the missing high speed orifice plug for the carb. I did the compression test this morning without the fuel pump, and carb attached don't know if that will effect my numbers but only gained a few psi on each cylinder, With a bit of luck all of this will help it out. Motor was free with the boat so I don't mind to spend a little bit. If none of this helps I'll sell it for parts and find something else.

Redacted

Got all my parts cleaned and replaced including hoses, carb, and fuel pump. Fired up on the 2nd pull, and running like a champ. Just need to dial in the carb on the water and we'll be all set. https://youtu.be/iHjh1SSMDQU

Sounds good. Those motors have a good reputation for being tough.


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https://youtu.be/AYAw7XClL_U

On the water, tops out at 15. Still have to add balast up front. Runs fantastic.