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JMN412 01-09-2013 06:13 PM

Outboard Issue
I have a 1978 Johnson "Seahorse" 8hp outboard, and she starts, but won't idle for long. I think it is just a dirty carb, but I was wondering if anyone knew where I could find a copy of the service manual.


dabnis 01-09-2013 06:36 PM

Re: Outboard Issue
You might try a Google search, IIRC, there are lots of sites showing parts and diagrams.

Paul T

Sea Dawg 01-09-2013 07:23 PM

Re: Outboard Issue
I go with Seloc. Common sense words in there. I built a Johnson 135 HP with no prior experience with outboards and found all the advice in there worthy. About $27 on Amazon.

denverd0n 01-10-2013 12:00 PM

Re: Outboard Issue
I found this to be a good source of information and parts for my Johnson Seahorse, including service manuals...
Outboard Motors, Boat Parts, Marine Engines, Inboard Boat Motor

tschmidty 01-10-2013 12:46 PM

Re: Outboard Issue
I have never found a real service manual online, but there is a lot of good info at this site.

FWIW, it could quite possibly be a dirty carb, but replacing spark plugs is a good, cheap thing to do. You can always just test the resistance and clean the contacts also. Run through that site for some other ideas.

JMN412 01-10-2013 10:40 PM

Outboard Issue
Yeah I have been using the leeroyshamblings website, it has been helpful but I wish the exploded view pictures were labeled.

Quick update: I made a fresh tank of fuel, replaced the spark plugs, cleaned the carb, and checked the fuel lines and fuel filter. It turns out that the piece that controlled the idle broke off, so I am going to try to find a replacement for that. But even when I manually control the idle it still stalls. Could it be a fuel mixture issue? Any thoughts?

Minnewaska 01-11-2013 05:24 AM

Re: Outboard Issue
Are the spark plugs gapped properly?

chucklesR 01-11-2013 09:58 AM

Re: Outboard Issue
You say it won't idle for long - does it run at higher RPM's?
If so adjust the idle to where it will run.

Forgive me for asking the obvious - but you didn't mention them:

Is the choke released (not just in, but really, you might have a bad linkage).
Check the air filter (remove it and try).

dabnis 01-11-2013 01:56 PM

Re: Outboard Issue
Assuming everything else is OK it sounds like it may be a mixture problem. If it idles smoothly and then just dies, it may be too lean. If it idles roughly with a fair amount of smoke, it may be too rich. On the many outboards and motorcycles I have had the sort of "one size fits all" setting was 1-1/2 turns out from being closed. At idle, richen it up until it starts to stumble a little then lean it out just enough to get rid of the stumble. I like them just a little on the rich side.

Paul T

Brewgyver 01-11-2013 03:10 PM

Re: Outboard Issue
Plus one on the dirty carb. It would also help to know how LONG it will run before it dies. Could be junk in the bowl, blocking the idle jet after starting. If it runs for a few minutes, could be the float sticking.

I would start with the carb bowl drain (if it has one). With tank disconnected, and a small white cup placed beneath, remove the drain screw. It can be a tight squeeze to get a cup under the drain, but get something there, to see if you get any grit or gunk out. If it runs clean, remove the carb, disassemble and clean.

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