Prob with 18h seahorse

[kakanur]

Ok my motor is a 1958 Johnson 18h seahorse, the serial number is 1691861. and the model number is FD-12 The first time I had it out this year, it started up on the second pull and ran perfectly the entire day, the next time I had it out, it was sputtering the entire time, kinda sounded like it would if it were runnin out of gas, so I checked the hoses and the tank, and everything looked all right, next time I had it out, it started up fine and sounded good, it wasn’t sputtering anymore, so I opened her up to head across the lake, but for some reason it's top speed was only about 4.5 mph, and I couldn’t get it to go any faster, usually my top speed is right around 20 mph. and it's been doing it ever since, what could be the problem?<br /><br />Thanks <br /><br />~Ryan

 

[alcan]

Re: Prob with 18h seahorse

Hi Kakanur<br />It sounds like your motor may be running on only one cylender. When was the last time you tuned her up. I would pull the flywheel and inspect the magnito coils, see if they are cracked or leaking. Then replace the points and condencers. Then clean carb and filter, check o-rings in the fuel line connector, replace o-rings if neccesary. Might as well replace water pump empeller and change gear lube. If you don't allready have a manual, better get that first.

 

[JB]

Re: Prob with 18h seahorse

Howdy, Kakanur.<br /><br />I believe that the FD-12 has a high speed mixture adjustment. You may be running too rich and "four cycling". Try turning the high speed jet in (CCW) about 1/4 turn at a time and see if that causes her to pick up.<br /><br />As Alcan points out, you may also be running on one. The quick way to find that out is to pull the plug wires one at a time and see if it makes any difference. No change = dead cylinder.<br /><br />Let us know what you find.

 

[kakanur]

Re: Prob with 18h seahorse

Thanks for the replies guys...<br />JB adjusting the high-speed lever did help some but I still maxed out at about 6.5 mph, so I guess it must be the cylinder?<br />Now, I have never worked on this motor before, or any other outboard for that mater, so I am going to need a manual, witch one should I get? And where can I find parts for this motor?<br /><br />Thanks

 

[alcan]

Re: Prob with 18h seahorse

Hi Kakanur<br />There are several good manuals available. An after market Clymer #B734 is one. Of course the oem is better. You can order one from Iboats,buy one at a dealer or marine store,or many public librarys have manuals (free).

 

[fireman 757]

Re: Prob with 18h seahorse

remove the cover and see if you hear a popping sound. My 1956 evin 18hp had a bad ignition coil.. It would arc at high rpm and you will not get the proper spark to the plugs. If you need to replace it they are about 40 bucks.

 

[oldboat1]

Re: Prob with 18h seahorse

first guess would be fuel problem -- maybe water in the fuel. Start with a fresh tank with fresh gas and oil in the right mix (about 24:1), and see if the problem clears up.

 

[Yepblaze]

Re: Prob with 18h seahorse

Put some fresh spark plugs in it.