Topic: 1968 3 hp evinrude hot? – Antique Outboard Motor Club,Inc

This topic has 13 replies, 10 voices, and was last updated 5 years, 9 months ago by billy-t.

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July 19, 2018 at 9:23 pm #10601
billy-t
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Okay so I have a 3 hp evinrude, actually a couple, but one seems to run hotter than the other. The flywheel gets warm/hot to the touch. you can hold your hand on no issue but the other one runs cool to the touch. I have checked the passages, changed the impeller and it seems to pump water fine, check the water line no blockages or holes in it.

Some folks here suggested I was running them to lean, so going back to 16:1

Going to to a test run in the barrel tonight, with the digital thermometer what temperature should i expect to get off the cylinder head away from the exhaust plate?

Any thoughts are always greatly appreciated.

Cheers

Billy T
July 19, 2018 at 9:44 pm #79741
jerry-ahrens
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US Member
You need to run those JW motors at 16/1 for sure, they need the oil. Just a guess, is your impeller housing worn out? How about the stainless wear plate under the impeller, is it grooved out? You can pick those up on Ebay sometimes for a reasonable price. Running in a barrel may not allow the motor to cool properly either, since your cooling system water is aerated with spent exaust gases.
July 19, 2018 at 9:56 pm #79743
billy-t
Participant
Thanks Jerry, I can check the housing again, didn’t really note issues but something is going on. It was running hot on the lake, not in the barrel so i think there must be something I am overlooking start with the impeller housing.

Thanks for the thoughts
July 19, 2018 at 10:10 pm #79744
frankr
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US Member
Are they both 1968?

A couple of places to check if it actually is getting hot are: There is a small horizontal hole at the top, accessed by removing the flat exhaust cover plate. It is only about 1/8" diameter (guessing) and easy to get plugged up by trash. Also, there are passages at the powerhead base that get plugged by corrosion (probably more of a salt water thing, but who knows?)

I’d check the cylinder temp instead of the head. The head gets pretty hot because it is only cooled around the edges.
July 19, 2018 at 10:39 pm #79746
Mumbles
Participant
Something else to watch out for on the smaller motors is the water tube. Being made of soft copper, it can get bent quite easily while reinstalling the gearcase and then rub on the spinning driveshaft causing a worn spot which will eventually wear right thru causing a massive water leak. Water meant for cooling purposes can’t do its job if it’s hemorrhaging out of the water tube.

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July 19, 2018 at 11:30 pm #79749
foot_doctor
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Whoops, he told us the answer. The flywheel gets hot. I suspect that the laminations for one or both coils are protruding too far and are rubbing on the inside of the flywheel. The heat sink path along the crankshaft to the flywheel is pretty long. I"m betting on the coil laminations. R.T.
July 20, 2018 at 1:46 am #79755
bob
Participant
I agree with foot doctor.Take the plug boots off the spark plugs and turn the flywheel by hand and listen for any scraping.If you hear a noise then it’s the coils/laminates hitting the flywheel.If no sound,then it is possible that the flywheel nut is too tight.I believe it should be torqued at 35-40 lbs.If too tight it can make your motor strain to move the drive shaft making everything on your motor run hotter.
July 20, 2018 at 5:09 am #79759
garry-in-michigan
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Lifetime Member
30 to 40 is right. . . 😎
July 20, 2018 at 10:21 am #79763
enrico-italy
Participant
I have a lot of OMC 3&4 with VTR upper cover from 1968 thru 1975 and ALL runs very hot.

I suppose the reason is the flat exhaust plate without cooling interspace on it .

On the older 3 the the metallic airbox fixed on it act as an "heatsink" , and the lower open cover allows a good recirculation of air…

The covers of 1968/3 and following 4 are completely sealed …
July 20, 2018 at 12:41 pm #79767
lindy46
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US Member
quote foot_doctor:

Whoops, he told us the answer. The flywheel gets hot. I suspect that the laminations for one or both coils are protruding too far and are rubbing on the inside of the flywheel. The heat sink path along the crankshaft to the flywheel is pretty long. I”m betting on the coil laminations. R.T.

If this is the case, the throttle lever should back-off on its own. So my question to Billy T: do you have to keep adjusting the throttle? Does it slow down on its own?
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