Johnson Seahorse 18 Questions!!

[LucasalumacraftFD]

Hi Everyone,
I just got a Alumacraft "flying D" 14 foot boat with a 1958 Johnson Seahorse 18 motor. I had a few questions about the levers on the front of the engine. I can't seem to make out what they do and where they should be set for both starting and normal operation. I've included a pic so you could see the levers. The round one is the choke but the other two I'm unsure of.

Second questions is what is the proper oil and oil mixture for this engine?

Lastly I ran this engine in a trash can and after a short period of running I noticed this gray sludge on top of the water. Is this normal for these old motors? It hasn't been run for a while and i'm not sure the history on it but the guy did say he had $400 dollars worth of work done on the lower unit......I took a pic so you could see...

Any help would be greatly appreciated and this is really an awesome site!!!! Thanks

 

[Joe Reeves]

Re: Johnson Seahorse 18 Questions!!

(Carburetor Adjustments - Two Adjustable N/Vs)
(J. Reeves)

Initial settings are: Bottom high speed = seat gently, then open 1 turn out. Top slow speed = seat gently, then open 1-1/2 turns.

Setting the high and low needle valves properly:

NOTE: For engines that DO NOT have a shift selection, obviously there is no NEUTRAL position. Simply lower the rpms to the lowest setting to obtain the low speed needle valve adjustment.

(High Speed) Start engine (it will run pretty rough), shift into forward gear, take up to full throttle. In segments of 1/8 turn, waiting for the engine to respond between turns, start turning in the bottom high speed needle valve. You'll reach a point whereas the engine will either start to die out or spit back (sounds like a mild backfire). At that point, back out the needle valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest setting.

(Low Speed) Slow the engine down to where it just stays running. Shift into neutral. Again in segments of 1/8 turns, start to turn the top needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running. Eventually you'll hit the point where the engine wants to die out or it will spit back. Again, at that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustments, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

 

[jbjennings]

Re: Johnson Seahorse 18 Questions!!

Hi Everyone,
I just got a Alumacraft "flying D" 14 foot boat with a 1958 Johnson Seahorse 18 motor. I had a few questions about the levers on the front of the engine. I can't seem to make out what they do and where they should be set for both starting and normal operation. I've included a pic so you could see the levers. The round one is the choke but the other two I'm unsure of.

Second questions is what is the proper oil and oil mixture for this engine?

Lastly I ran this engine in a trash can and after a short period of running I noticed this gray sludge on top of the water. Is this normal for these old motors? It hasn't been run for a while and i'm not sure the history on it but the guy did say he had $400 dollars worth of work done on the lower unit......I took a pic so you could see...

Any help would be greatly appreciated and this is really an awesome site!!!! Thanks

The other two knobs are for the high and low speed carburetor adjustments and Joe's method is great for setting them right. Ignore the numbers on the knobs and faceplate--they're almost worthless. You can push in on the Faceplate and get it to go around further in order to get it all the way seated----don't forget to seat (close) the needle valve GENTLY.

Your fuel/oil mixture should be 24:1 and will make less sludge if you use the synthetic. I use the pennzoil stuff when I can find it.
It's perfectly normal to get a lot of crud floating on top of your barrel. It's just unburnt fuel and oil. It shouldn't be quite as bad when you get your carb. adjusted right but will still make you frown a little.

BTW, welcome to iboats and remember to post a full picture of your new rig next time! I love to see 'em. Especially with a '58 FD12 on the back of it!
Happy boating,
JBJ

 

[Sea18Horse]

Re: Johnson Seahorse 18 Questions!!

nymarine.ca has the decals and other items for that motor if you get a wild hair and decide to restore it.

TCW3 certified outboard oil is the stuff you want. Any brand works fine. Many people here use walmarts house brand with good results and it's cheap. Full synthetic will smoke less and is said to be more biodegradable. I'm not sure if I buy that myself. Yes these old engines are very dirty. Lots of unburned fuel and oil goes out with the exhaust. So that goo is perfectly normal. I like to corral the stuff in a corner when it's idling and scoop it out as I go :shrug:. 24/1 is the prescribed fuel/oil mixture. However that engine is fully jeweled meaning it has needle or roller bearings throughout. Rather than plain bushings. So it's said you can safely use 50/1. You'll just have to decide for yourself if the smoke and whatnot is too much to handle on 24/1.

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

 

[cougar1985]

Re: Johnson Seahorse 18 Questions!!

have a couple of those babies myself though on my 58 i changed the cowling to the 57 as i like the color scheme better.my own personal opion is that the 57 /58 johnnys are one of the best motors ever made ,period.