Johnson 4hp seahorse

[TerribleCJ]

Picked up a 70's or 80's seahorse yesterday. It really looks like it has never seen the water, It looks brand new as does the original omc gas tank. The guy said it overheated and he never bothered to check it out. I'm not sure if it was impeller problem or if it was a bad gas mix. As good as it looks, I doubt the impeller failed. I could be wrong....I'm assuming theres nothing I can do with this motor? Is it a matter of replacing piston rings or is it deeper than that....Never went that far but my stepfather is a fabricator and builds many motors so the work isnt an issue. I recently brought a 63' evinrude lightwin back from the dead and I'm looking to start a new project. Also got a 1958 Scott-Atwater yesterday as well. The Johnson just looks too good not to run....

 

[lindy46]

Re: Johnson 4hp seahorse

Is it locked up?

 

[Rick.]

Re: Johnson 4hp seahorse

First thing I would do is check the compression of each cylinder. Your impeller could well be the problem as they fail due to age more than use. Let us know what your numbers (model and compression) are. Best of luck. Rick.

 

[kfa4303]

Re: Johnson 4hp seahorse

+1. Check the compression first. Spraying a bit of WD-40, or Deep Creep into the cylinders can help free things up a bit.

 

[TerribleCJ]

Re: Johnson 4hp seahorse

Model # is 4w75 I believe

 

[TerribleCJ]

Re: Johnson 4hp seahorse

Model # is 4w76 I believe

 

[Rick.]

Re: Johnson 4hp seahorse

So that is a 1976. Fantastic engines and so dependable. I've got a 71 Evinrude that has had some issues this summer but all is well now and I'm enjoying it again. Use mine for trolling and the fuel consumption averages about a liter per hour. Only drawback is it doesn't have a neutral position. Does the 76? I have seen several from the 80's that do. Hope you get good compression numbers. Rick.

 

[TerribleCJ]

Re: Johnson 4hp seahorse

No neutral as far as I see. I pulled the head cover off and it looks like there is sand clogging areas of the water channel. I'm guessing someone ran it into the ground and sucked a bunch of dirt through there. I pulled the lower unit (one of the bolts snapped but the others were no trouble) and it looked dirty. I turned the prop and the driveshaft turned fine and was puffing out dust from the outlet. The impeller housing screws werent going anywhere. I'll need to wait for a hand to get those off. I sprayed them with pb for good measure. Might need to heat it a bit.....How much of a pain is it to get to the con. rods? I'd like to pull the pistons and soak everything...

 

[Rick.]

Re: Johnson 4hp seahorse

You should get an OMC service manual if your going down that road. Personally I wouldn't until your sure you need to. With the head off you can jerry rig a garden hose to the water tube and flush the sand/dirt out of the passages. A liitle poking with wire or what have you might help. Use lots of water to clean up the lower unit as well. Rick.