Just got a 1957 18hp johnson seahorse

[iowa84]

I just bought a 16 ft john has a 1957 18hp johnson seahorse. They guy says it runs but it is hard to start. I am going to put new J6C spark plugs on it and clean the carb. If that doesn't help I will need some more suggestions which I think one problem could be the ingnition coils going bad.

 

[1946Zephyr]

Re: Just got a 1957 18hp johnson seahorse

Well, you just got one of the most reliable motors ever built. I've had a few in the past. One thing you could do, is pull the stasrter assembly and the inspection plate off of the top of the flywheel. There, you'll be able to get a good visual of the coils and see if there is any cracking on the coils. If there is, they'll need to be replaced. Come on back and let us know what you find.

Welcome to iboats.

 

[iowa84]

Re: Just got a 1957 18hp johnson seahorse

Tomorrow I am going to get new champion J6C spark plugs for it and hopefully be able to check and see of those are cracked or not. This is my first boat and I have heard that this motor is very reliable a classic and starting to become a collectors item especially the cherry red colored ones like what I have.
I do appreciate any help given to me, I know very little about boat motors except how to drive them. Far as the motor goes I am sure it's pretty much common sense but I am gonna make sure of what I am doing before I do it because I do not want to mess this motor up.
This motor will be pushing a 16 ft flat bottom john and from what I hear this particular motor will scoot. The more I hear of it the happier I am with the buy, was skeptical about how old the motor was.
What do I gage the spark plug at? I read .040 somewhere and want to make sure.

 

[1946Zephyr]

Re: Just got a 1957 18hp johnson seahorse

Yea, the old 18's from the late 50's were actually the best motors built. There isn't any of the plastic parts to speak of and none of the fancy high dollar electronics to break your wallet either. These motors are approaching 55 years old and ones in good condition are still offering top notch reliability. That should scoot that john pretty good. Set the plugs at .030. Some would say to set them at .040 for trolling to prevent fouling. I never tried that, but others here will speak from experience.

 

[lindy46]

Re: Just got a 1957 18hp johnson seahorse

If you do a lot of trolling, set the plugs to .035". My 18hp would consistently foul at .030" - .035" solved the problem.

 

[kbait]

Re: Just got a 1957 18hp johnson seahorse

Check out 'Top secret files' sticky at the beginning of this forum. Loaded w/great info!

I've had a bunch of 18's over the years. Properly tuned, they'll idle like a sewing machine and run out like a scalded dog. I ended up switching to a '75 15hp Johnson for my deep 14' alumacraft, as it just sips the fuel, and still pushes 2 people to 18mph... but when it's calm, or 3 in the boat, I miss the top end and raw power of those 18's. And I can't knock my kids out of the tube anymore

.. Change out the fuel/air lines under the cowl with 5/32" hose if yours are original or hardened. You can also change out the o-rings in the fuel line coupler if yours are leaky. Start a new post if you want help doing that. Good luck and have fun!

 

[iowa84]

Re: Just got a 1957 18hp johnson seahorse

Thanks for this tips everyone. I am not sure if everything is orginal since I don't know the full history. But I will post some pictures as my work begins.

 

[iowa84]

Re: Just got a 1957 18hp johnson seahorse

Have spark but no start. It is getting fuel but the plug that runs from the gas pump that connects to the male plug is leaking, I most likely have to replace that. Since it is leaking, how does that effect anything? Does it lose pressure? Next step is replace that and see where I can go.

What it is doing when I try and start: It just turns over and it kicks like it wants to start BUT only after i stop pulling for a couple minutes..if i keep pulling it just makes a normal sound of turning over, when i let it sit for that couple minutes it sounds as if it wants to start popping off, any suggestions? I also found out that the shear pin is broken at the prop. Sunday I will get to the carburator, i wanted to today but it didnt happen..< comments to naggy ol lady lol

 

[lindy46]

Re: Just got a 1957 18hp johnson seahorse

Bad o-ring in the fuel line connector - they will need to be replaced. If it were my motor, I'd change out the cracked coils and rebuild/clean the carb. Then she'll run like a champ.

 

[iowa84]

Re: Just got a 1957 18hp johnson seahorse

I didn't look at the coils yet but it has spark so I just assumed they are good, Should I still check them? I am gonna clean out the carb real good ill go to the marine today to get that fuel connector

 

[Steve A W]

Re: Just got a 1957 18hp johnson seahorse

Iowa84
Check the coils,if they havent been changed they are probably bad even if they have spark.
Here's a few links that will be helpfull, I learned a lot from them.

http://www.precisionservoutboard.com/Information/ArtsFivePointPlan/tabid/65/Default.aspx

http://forums.iboats.com/showthread.php?t=158086

http://www.duckworksmagazine.com/07/columns/max/articles.htm

I recently got the same motor and am working on it now.
I'm also putting it on a 16 foot jon. I can't wait to try it!
Good Luck
Steve A W

 

[Sea18Horse]

Re: Just got a 1957 18hp johnson seahorse

I didn't look at the coils yet but it has spark so I just assumed they are good, Should I still check them? I am gonna clean out the carb real good ill go to the marine today to get that fuel connector

Just out of curiosity how did you check for spark? If you just stick a spare spark plug in the wire end and hold it against the block that's not a valid test. You need to make sure that it will jump a 3/8" gap. Only then can you be sure that the ignition will supply enough power to start the engine. Even nasty old coils will have enough to jump a .030" gap in the open air. But they won't do it under compression. Good luck!

Cheers...................Todd

 

[samo_ott]

Re: Just got a 1957 18hp johnson seahorse

Yes, you must check the spark properly. You can get a good tester for under $10 at autozone or harbor freight I hear. You have a great engine. I love the 18's and have many. You really need to pull the pull starter and check the coil condition though. Usually they're cracked and no good anymore.

 

[iowa84]

Re: Just got a 1957 18hp johnson seahorse

The one spark plug I could see the jump on but the other i couldn't but I just held it and took the shock. I think I am going to replace the coils just to know that they are new instead of wondering when they will go out. I can't wait to get this motor running and out on the water, with everybodys help on here I am sure I will have it going in no time. When I get that done all I gotta do is try to find the right color paint for it and make it look good as new after all it is a very classy looking motor.

 

[iowa84]

Re: Just got a 1957 18hp johnson seahorse

one more thing, are the coils on this motor considered ignition coils or are they just called coils? I need to order them and I don't want to have the wrong thing shipped if anybody knows a link for this 1957 18hp johnson seahorse please let me know.

 

[BassBlaster29]

Re: Just got a 1957 18hp johnson seahorse

I'm not an engine restorer but I have been doing alot of research since I just picked up a 56 10 horse. I found a site called nymarine.com. They have all your paint and decals for your motor and your gas tank. I found complete tank rebuild kits on ebay for 35 bucks and most of your motor parts are right here on iboats.

Heres a link to your coils. You need 2 of em. i just ordered a set myself!!

http://www.iboats.com/mall/partfind...gd_poid=109172&gd_row=72&**********=331011270

Might as well get the tune up kit and do that while you have her opened up too.

 

[iowa84]

Re: Just got a 1957 18hp johnson seahorse

Thanks a lot, I found these coils once and some reason couldn't find them again. much appreciated I will have to check out the nymarine.com and see what they got

 

[1946Zephyr]

Re: Just got a 1957 18hp johnson seahorse

I'm not an engine restorer but I have been doing alot of research since I just picked up a 56 10 horse. I found a site called nymarine.com. They have all your paint and decals for your motor and your gas tank. I found complete tank rebuild kits on ebay for 35 bucks and most of your motor parts are right here on iboats.

Heres a link to your coils. You need 2 of em. i just ordered a set myself!!


http://www.iboats.com/mall/partfind...gd_poid=109172&gd_row=72&**********=331011270

Might as well get the tune up kit and do that while you have her opened up too.

Yea, I love their decals and paint selection.

As for the coils, their easy to find. Napa has them and so do any of your marine suppliers. They were widely used in OMC twins and singles, from 1951, to 1976.

 

[iowa84]

Re: Just got a 1957 18hp johnson seahorse

The coils are in working condition from what I found out. Now my problem is the female fuel line connector that comes from the tank, I can find it and I need it ASAP if you know where I can get this please give me a direct link to it, the part number on it is 376341 the o-ring in it has gone bad and I dont know what else to do besides get the fuel connector. if you now how to replace it please help.

 

[Steve A W]

Re: Just got a 1957 18hp johnson seahorse

You'll find a parts break down here;
http://www.marineengine.com/parts/parts.php

Here's a link to a fuel fitting on ebay;
http://cgi.ebay.com/ebaymotors/ws/e...viewitem=&_trkparms=clkid=7688105421329132145

Good Luck
Steve A W