Compression Test on 1962-3hp Johnson Outboard Part 1/2

How to test the compression on your outboard motor.

[@chrilla1980]

Thanks and sorry for the late answer but i managed to fix it myself as i also mentioned in one of your newer videos.The impeller was fine but previous owners had put together a rubber seal the wrong way so it blocked the cooling channel. People like you are really really great that actually answers his/hers subscribers because sad too say not many seems too bother answering these days. You are awesome and i love your videos. Cheers and take care

[@donyboy73]

yes thanks, i did manage to get it going again

[@donyboy73]

@snaponjohn100 it's pretty hard, usually a leak down test will tell u where it's leaking. i rarely do those leak down tests. i usually go by feel by pulling the pull starter slowly

[@donyboy73]

yes got it running and it is sold

[@Genners111]

To answer your question: yes, parts are still available for these. There are lots of exploded diagrams of, say, the powerhead, online and it tells you the OMC part number (or equivalent). I sourced all mine from eBay as these were popular motors back in the day, and another plus is that from 1953-1967, they were pretty much the same, and parts are very much interchangeable! Good luck!

[@donyboy73]

@VintageOutboardMan thank you

[@fleetwin1]

Those old 3hps do not have that much compression to begin with...Keep in mind that the long hose to the gage has a downward effect on the compression readings, especially those small combustion chambers. I would soak the pistons, true up the head/block surfaces, replace the head gaset....And, I'm betting the engine will start and run, compression will probably improve after you have run it for awhile...

[@donyboy73]

I replaced the rings and it runs well

[@plm947]

Thoes motors will run fine with compression between 70-80 pounds. Why don't you replace the head gasket put the motor on it's face so the pistons are pointing upwards. Then level the pistons out so the ports are covered. Then pour some Sea Foam in the cylinders and let it soak down past the rings. It may take a few days to a few weeks to soak down past the rings. But I've brought back many a motor this way

[@donyboy73]

@Chaps1boy yes thank you, i forgot to do that

[@snaponjohn100]

Great video. How can u tell if an engine has compression relief valve for easy starting? I was told that if it has that, compression test will always appear to fail.

[@donyboy73]

yes it takes gear oil, you probably need a new seal somewhere

[@MattsRageFitGarage]

Cool video ! thumbs up !

[@snaponjohn100]

Hey Don. How do u perform compression test on a newer mower with a pressure relief cam?

[@dkruitz]

Sure you can get rings - you may not even have to replace them - they could be stuck from carbon. Also those bolts and washers are not original and they seemed to come off very easy - it's possible the head gasket is bad and wasn't torqued down enough. Be sure to ground those plugs or you'll fry the coils.

[@donyboy73]

@fleetwin1 look at part 2

[@ducklandwikeno]

Yes you can get rings for it by the way . Im rebuilding my evinrude 7.5 fleetwin 1957 . Im replacing the rings and head gasket too . Did you ever get it running .

[@fleetwin1]

Believe it or not, those old 3hps didn't have alot of compression..60PSI is a little low, but would probably run...Maybe the rings are just stuck, a good soaking with engine tuner or some other decarbonizing fluid will probably help free it up...

[@vinnitca1990]

Good video Thanks !!!

[@donyboy73]

@1890scooter843 just touch it to the motor

[@donyboy73]

the new ones are plastic, check at your local marina or boats dot net

[@j-somebody6384]

Thanks, your right that's it.

[@ralphlefebvre9478]

I'M pretty sure it was the head gasket . taking it off to change the rings and then putting one on new was enough to do the job . 3HP does not have a ton of compression and the fact that it was only 10# different says gasket to me .

[@chrilla1980]

Dony...do you know where to find an impeller to my johnson 5.5 from 1962?(Seems abit hard to find here) And it would ofcourse be great if the shipping is available to Sweden as it´s where i live

[@donyboy73]

@CoRRisioN2142 i have the follow up video i am uploading tomorrow

[@Genners111]

(the motors from 1953-1967 were very similar, rather, with minor variations).

[@VintageOutboardMan]

The compression should be around 85 psi. By the way, your outboard is a 1965, not a 1962...

[@Genners111]

Yeah this is a '65, not a '62: the numbers after the JW usually ascended by 1 with every year (though sometimes they re-used the same number for two years) -- for example, mine is a JW-21E and is a 1966. If it were a '62, it would be a JW-17... and have 2 needles (high and low). Check out the vid on my channel where I did a restoration of above-mentioned Johnson JW-21E :-)

[@1890scooter843]

How do you ground the spark plug? I need to check the compression on my 68 20 hp johnson

[@donyboy73]

thanks for watching!

[@j-somebody6384]

Dony, whats the point gap for for 1950 johnson seahorse tn26 ???

[@j-somebody6384]

I can't get my GEAR OIL, to go into the gear casing, it comes right back OUT, of my 1950 Johnson seahorse tn -26 IT DOES TAKE GEAR OIL, DOESN'T IT, NOT SURE???????

[@DatBlueHusky]

looks like that motor might have been at the bottom of the lake at some point lol but save it dont part it out try rehoming the bore and free the rings

[@sideshow45]

my kohler makes 57, im surprised it runs at all. it runs really good, actually haha.

[@j-somebody6384]

I am looking for a cork float, that's what it takes, it's a 1950 Johnson seahorse 5hp TN26, if anyone knows, where I can get one let me know.

[@CoRRisioN2142]

soak the cylinders with sea foam and pull it try and get those rings unstuck

[@donyboy73]

guessing .020

[@mumbles552]

Please, please don't crank them over without grounding the spark plug leads. The high voltage needs somewhere to go and if they aren't grounded the high voltage will short out in the coils making them useless.

[@WillsGarage91]

Model JW-20B is a 1965 model

[@donyboy73]

ask youtuber "classicoutboards"