1959 Johnson Seahorse.......

[WNGCHASIN]

Hello All, I am new to this forum but was refered over this way for some great knowledge.

A little background: I recently got a 1959 Johnson Seahorse 18. It would start, run in both forward and reverse but would not idle. Took it to a shop which I thoght was reputible and here I am now.

Work the shop has done:
Comp test, 103 and 102
No spark in one cylinder, points and coils cracked and corodid, both points and coils replaced
Carb cleaned and new carb kit used to rebuild
New plugs installed

Motor starts runs and idles good. The problem is I cant get more than 12.5 mph (on my gps) out of it on a 12 foot flat jon. The motor dosent seem like it is reving up all that high.

For a comparison on the same boat I am running my friends late 50's early 60's Evinrude 15. with the same load in the boat I am getting 20 mph.
I also bought a in-line spark tester and am getting the same amount of spark out of each cylinder.

Any thoughs as to what I should have them (the shop) do or look at when I take it back. I will be taking it back as they told me if I have any problems to bring it back (had to do once because the set the float wrong) and they will make it right.

Thanks in advance, and great site too.
Brent

 

[oldrudedude]

Re: 1959 Johnson Seahorse.......

If the engine is in good mechanical condition and in good tune, perhaps the pitch of the prop is too steep for the load. This may be preventing it from reaching peak rpm. (like trying to drive up a steep hill with your car in high gear.)

 

[samo_ott]

Re: 1959 Johnson Seahorse.......

That sure sounds like a firing on one cylinder classic story. You say you're sure that the spark is good? I would still pull off each plug wire while it's idling to verify that the engine rpm's dropped evenly and that each cylinder is contributing equally. If so then you have another issue.

Have you tried adjusting the high speed knob on the carb while running it? Even though the carb was redone, that is the other area to look at. You have compression. If you have good spark, then it's pretty much gotta be carb.

Also verify that the carb is in sync with the ignition timing. i.e. a link n sync. Search on this forum on how to do it.

I have the same engine (in the shed - not running though) and many other 18's and they will all get me (240 lbs) in my 14' aluminum boat over 20 mph.

 

[coolguy147]

Re: 1959 Johnson Seahorse.......

check spark i really wouldnt pull the plug out whilte its running its very dangerous. you wont let go of the plug in time for you not to get shocked. trust me very painful i probably couldnt let go for about 2 seconds. get a spark tester which i believe is the safest way and i should get one myself

 

[samo_ott]

Re: 1959 Johnson Seahorse.......

Use a spark plug puller. They work great. No zaps!

 

[Chinewalker]

Re: 1959 Johnson Seahorse.......

Just because you have spark does not mean it is running on that cylinder. It's possible that since the compression test was done that the head gasket has blown - check the plugs for beads of water...

 

[WNGCHASIN]

Re: 1959 Johnson Seahorse.......

Thanks for the info guys. I will take it all into consideration. Didnt think about the head gasketeither, I will check the plugs.

 

[cougar1985]

Re: 1959 Johnson Seahorse.......

nowheres in your post do i see any reference to adjusting jets on the water.though you can get very close on land you need to do your final adjustments on the water.for an example i redid a 1970 33 hp evinrude tiller drive and ran greatttt in the barrel but when on the water it was very slow so opened the front of cowling and after a slight adjustment on the high speed needle it ran like a scalded cat.just remember not to over do it in any direction and with either the low or high speed adjustments.every motor is differnt and every motor will respond to adjustments differntly,some with as little as 1/16 a turn some a little more.ive got many outboards with high /low adjustments and no two react the same with the same adjustments.you will know when youve gone to far the motor will tell you with either a rich cough or lean sneeze.

 

[samo_ott]

Re: 1959 Johnson Seahorse.......

They still had adjustable high speed jets in 1970? I thought they were long gone by then!

 

[cougar1985]

Re: 1959 Johnson Seahorse.......

They still had adjustable high speed jets in 1970? I thought they were long gone by then!

not on my 33 rude ,still has both high and low speed adjustments.

 

[jdsgrog]

Re: 1959 Johnson Seahorse.......

Yeah, sounds like the jets. Adjust the high speed jet. Bet you're running too rich.