1970 Evinrude 1.5hp wont run slow, only fast

[OttawaPhil]

Good day gentlemen,
Thank you in advance for sharing your knowledge.
I just bought a used 1970 Evinrude 1.5hp that seems in great shape.
It starts and runs great near full throttle. But if I try to slow down it stalls soon after.
Tonight I am going to take it apart. In your experience, are there any specific things I should check? Was going to take apart carb and see if something is clogged or damaged in low speed jet. Anything else I should check? Probably just needs cleaning as it was not used much in last 5 years apparently.

Thanks!

 

[cajuncook1]

OttawaPhil, congrats on your new purchase.

1st thing I would check would be the compression. You can buy one for 10 to 15 dollars at Harbor freight or auto parts store. Some auto parts stores will even lend out a compression gauge with a refund deposit.

The late 1960's and early to mid 1970's Evinrude/Johnson 1.5hp to 2hp should have compression of >100 psi to run well and idle smooth. Now that being said, yes those little motors will run on PSI of mid to upper 80's to 90's, but will have less power and have difficulty running with idle or slow speeds.

Please don't start buying a bunch kits and parts until you have evaluated the compression. If your compression is low, then the other diagnostic aspects of ignition or carburetor/Fuel delivery won't matter.

You tube video to show how to basically test compression.

https://www.youtube.com/watch?v=PyCw4SiuT2I

 

[Vic.S]

Check the compression if have or can beg, borrow or steal a compression gauge.

Check the spark

If you have the appropriate puller remove the flywheel and inspect the coil, clean and reset the points if there is any doubt about the spark

Give it a new plug, J6C gapped at 0.030"

Clean the carb See Joe Reeve's instructions for adjusting the needles on the Engine FAQs board ( follow the link from the "Top secret file" on this board)

Clean the tank and the filter on the fuel shut off valve.

use new 50:1 fuel

When all running nicely fit a new water pump impeller before you use it.

You should find its covered by one of the manuals at http://boatinfo.no/lib/library.html

 

[OttawaPhil]

Thanks guys, will check compression too asap.

 

[OttawaPhil]

Also what kind of oil can I use in the bottom? I am in canada so would like to get something from canadian tire if possible.

 

[F_R]

80-90 weight outboard motor gear oil. Canada has bazzilions of outboards, so it should be available most anywhere. As for your idle problem, make sure the carburetor throttle shaft isn't stuck in the open position. Easy to happen because it is sort of exposed to the elements on that motor.

 

[OttawaPhil]

Thanks, will get that on way home too.

 

[Tim Frank]

Motomaster Formula 1, SAE 90 Marine Gear oil. Cat # 28-17004.

Their website allows inventory checks by store, so you can figure out whether the nearest one has what you need.

 

[OttawaPhil]

Compression is just over 100 psi. I have taken the carburetor apart and it's all clean inside already and even as what appeared to be new gaskets in it as if it was serviced recently. Put the carb back on and started it same behavior. checked spark and it is blue and visible in daylight. Not sure how to tell how bright it should be.
Any other ideas?

 

[OttawaPhil]

Oh and needles look good with no wear. One other thing of interest is that the rotating tab that moves to activate the throttle works from the start position to the fast position. Anything below start and the lobed sheet metal does not touch the plastic rocker thing that goes to the carb. Is that normal? Maybe it is, not sure. What should I check next?

 

[nwcove]

jmo, but i would clean the carb. the idle circuit on that little motor has some very small holes that could be gummed up a bit. as far as spark goes, a $10 adjustable tester from princess auto set to 1/4 inch gap is the true test .

 

[OttawaPhil]

I just remove the lower drain plug the one that's near the center of the propeller shaft right at the bottom. Only about a couple ounces of milkly brown fluid came out.

 

[F_R]

So now fill it up again. Have the filler plug hole "up" while filling. Yes the cam follower should leave the cam at idle speed position. There is a certain position that it is supposed to make initial contact. A line on the cam--if there is one. Otherwise, I'd have to get the book out. When the follower is off the cam, the throttle shaft should be completely closed (not stuck open as I asked earlier).

 

[OttawaPhil]

So I refilled the lower with the marine gear oil and reassembled it. Forgot to say before the throttle shaft moves freely. Carb is clean inside. I cleaned it too. Sprayed carb cleaner through the lower passages and I sprayed through easily.
I will get a spark checker next. Thanks for sticking with me and helping guys I appreciate it.
I have rebuilt multiple two stroke dirt bikes and never had this problem...

 

[F_R]

Never say never, I guess, but if it starts great as you said, and runs fast, you have spark and there is nothing really serious wrong up there. You have some kind of fuel / air / adjustment / problem. You say you cleaned the carburetor. So, we are at the guessing stage now. How far open do you have the idle needle? It would be reasonable to suspect there is a problem in the idle circuit of the carburetor. Maybe you need to take another look.

 

[Tim Frank]

Is the throttle butterfly closing fully?

 

[OttawaPhil]

Yes butterfly does close. It's hard to make sure idle circuit is good since the seat doesn't come out. I will take it off again and try again.

 

[OttawaPhil]

What i mean is the welch plugs keep me from seeing In low speed circuit well and I can't take them out since i don't have replacements. But I pulled needle out and shot the carb cleaner with straw through and fluid came out the other side.
Going to buy spark tester and do that tonight then take carb off again and clean it some more.

 

[Tim Frank]

Let me rephrase....does the butterfly STAY closed without you increasing the throttle?

 

[OttawaPhil]

Or do I need to take them out? And if so are the welch plugs just standard size? In stock at marinas or small engine places? Don't want to have to wait weeks for parts from USA if I don't have to?
Also if spark is weak then what puller can I use to remove flywheel? Harmonic balancer puller?