Johnson Sea Horse 3hp twin

[doug3386]

I have the unit ready for a test on the back of the boat in the pond.<br /><br />Can anyone tell me what the nominal settings are for the low and high speed jet screws. That is the number of turns out from the seated position?<br /><br />I used Tom Travis' article to set the timing and found it very helpful.<br /><br />The carb butterfly linkage arm was fatigued and broken, probably from overtightening the set screw. With a piece of flattened copper pipe I was able to cut and shape a reasonable facsimile that fit up fine.<br /><br />Are new motor parts available for this model from a source other than OMC? Just asking in case...<br /><br />Thanks for your help guys. I got it fired up and ran it for maybe 10 minutes or so on the pond but it seemed to be reluctant to idle. Well I pulled it out and noticed that it wasn't cooling properly. Pulled the lower end to check out the impeller. Decided a new one was in order and did a compression check as a matter of interest. It seems balanced - roughly +70 psi on both cylinders. Seems low. So has anyone any ideas on rings? Standard stock number is 486277. Know where they can be found?

 

[OBJ]

Re: Johnson Sea Horse 3hp twin

Hey Doug....got a year or model number? Kinda hard to say what's available with out a year.

 

[Paul Moir]

Re: Johnson Sea Horse 3hp twin

I would say 70 psi would be normal for an old 3hp. Decarb might bring them up but I've seen them happy as a clam at 55 (by my guage). Just a little hard to start.<br />I think as long as you've got your link&sync correct, your fabbed parts can't be a problem.

 

[doug3386]

Re: Johnson Sea Horse 3hp twin

Yes, OBJ, the model is a JW13.

 

[Paul Moir]

Re: Johnson Sea Horse 3hp twin

Many parts are available aftermarket for your '57. Ignition coils, points, condensors, head gaskets, carb kits (not as good as OEM, but I think the coils are better), impeller, lower unit seal kits, that sort of thing. Iboats, NAPA autoparts, various other online stores carry these.<br /><br />Dealer has entire water pumps, carb kits with floats to replace the cork ones, impeller keys, flywheel keys, propellers, various clips and bushings, all the gaskets, fuel connectors. Piston rings can be gotten (for a price!) either from specialty suppliers like nymarine.ca or from NOS (New Old Stock) dealers (check ebay frequently, outboard-parts.com, laingsoutboards.com, vintageoutboard.com). Generally speaking, NOS is a lot less expensive than fabbed, but the trick is to find parts. But I don't think you really need new rings anyway.<br /><br />With a bad idle I would first go over the carb, rebuilding it with a factory kit. Another very common problem is a missing screen over the mouth of the carburetor. (between the carb and the air-silencer) Seems some people thought this slowed their outboards down and did away with it. Third, a crankcase air leak might cause a bad idle. There's no crank seals so really all you're looking for is something caught in the reeds or someone improperly assembled the crankcase with the wrong sealant.<br /><br />To set the high and low speed mixture controls, follow Joe Reeves advice:<br /> Click here.

 

[doug3386]

Re: Johnson Sea Horse 3hp twin

Thanks for the tips, Paul. I have kitted the carb, new points and coils and water pump impeller. I was even able to find a main jet same diameter which I cut off to the original length, drilled and tapped to accept the handle as the original main was eccentric at the tip?? Don't ask me how some people are able to do these things! I am going to check the timing again before it goes to water just in case I missed something. I really appreciate all the info but at this point I am thinking that any real improvement will come from replacement rings to get the compression up. So if anyone has a line on some NOS stuff out there please let me know. BTW, how does this two stroke work if there are no crankcase seals? I assume that there is piston/crankcase port induction as on snowmobile and motorcycle engines. Last time I checked there are no valves.

 

[brendantownsend]

Re: Johnson Sea Horse 3hp twin

You may be interested in this restore oil selling on eBay.<br /><br />I have a 1985 Johnson 4hp outboard that had a slight rough idle though I thought was running AOK until I tried the stuff from this seller. It definitely worked for my old engine and the engine now runs as sweet and smooth as a nut.<br /><br />For 2-strokes you DON'T mix it with your petrol but just pour a good teaspoon-or-two into each plug hole of a cold engine, then work the flywheel slowly to distribute around the bore and down past your rings. Then clear out the excess and replace your plugs - though be warned about the THICK black smoke when you restart!<br /><br />Maybe worth a shot before you go to the time and expense of replacing your rings...<br /><br /> http://stores.ebay.co.uk/AMETECH-ENGINE-RESTORE-OIL_W0QQssPageNameZl2QQtZkm <br /><br />Good luck.<br /><br />Brendan Townsend

 

[Paul Moir]

Re: Johnson Sea Horse 3hp twin

I don't know how some people do it or get away with it. <br /><br />The 3hp engine uses plain bearings and oil slingers to seal the crankcase. Basically what that means is it uses the TC-W3 oil itself to seal. Needless to say, this is a big reason it needs to be run at 24:1. On the later 4hp engines (supposedly 50:1) they put a proper oil seal on the crank at the top, but not at the bottom.<br />This is a common reed inducted two-stroke engine w/ crankcase compression. It uses crossflow scavaging. It doesn't work like a (reedless) chainsaw engine, but your right it's like most snowmobile / motorcycle engines. Except I think most of those are loop-charged?<br /><br />Run a decarb if you haven't already, as these little engines are sometimes run with the wrong or far too much oil. The exhaust passages are kind of small and the rings will stick with too much of that.<br /><br />EDIT: One last idea - is the armature plate wobbling so bad that it's throwing off timing? If so there's a pretty simple fix.<br /><br />EDIT 2: One more idea Are you running Champion J6C plugs gapped at .030"?

 

[doug3386]

Re: Johnson Sea Horse 3hp twin

Thanks Paul, now I'm beginning to see clearly how this thing works and the logic for the low ratio oil mix. Something that no one else has volunteered. I will definitely be doing another chemical decarb and I will check the timing and component fastenment. Interesting when you can learn something new!!