79 9.9hp Johnson Seahorse Problems

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Pleaselunkers

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May 7, 2008
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Hi everyone, I'm new to the forum. I just started lurking here today because I just got a 79 Johnson 9.9hp Seahorse that has a problem staying running. It hadn't been run in a few years but the inside looks pretty clean and rust free.

Last week my grandpa and I hooked it up to the hose with the earmuffs and it wouldn't run. I went out and replaced the fuel line from the gas tank to the motor with a new bulb and new connections on both sides. We hooked it up and it ran like a top for about 10 minutes.

My girlfriend and I took it out on the river a few days ago and it ran beautifully for about 20 minutes. The next day it fired up after about 10 pulls. I let it sit on the trailer for a minute before putting it in reverse. I got about to the middle of the river and it died. I couldnt get it to start back up on the water after about a hundred pulls. It didn't smell flooded (not sure if that means anything).

After getting it trailered I hooked it back up to the hose and earmuffs. First pull and it started right up ran for two minutes then died. Pulled two more times and it started back up ran for two minutes then died. The bulb was still hard after it died.

I'm really unfamiliar with engines but want to learn to do some fixes on my own. I'm guessing I have some kind of fuel line problem, but I have no idea where to start. Can you guys give me some suggestions?
 
Theoutdoorsman

Theoutdoorsman

Senior Chief Petty Officer
Joined
Mar 6, 2003
Messages
669
Re: 79 9.9hp Johnson Seahorse Problems

The key words here is "hadn't been run in a few years ". Most likely you need to rebuild the carb. My guess would be that it's dirty and the float valve isn't able to do it's job. The fact that the bulb stays firm suggests that the fuel pump is working well. Can you, using a spray bottle, keep the outboard running via spraying a premix of gas/oil into the throat of the carb while it's running? If so, I'd recommend removing and cleaning the carb. Here's a couple links you should take the time to read over also. There's some very helpful information for you here. Welcome to iboats!!!!

http://forums.iboats.com/showthread.php?t=158076
http://forums.iboats.com/showthread.php?t=158086

Must have been typing when T.D was posting............... :)
 
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Pleaselunkers

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May 7, 2008
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Re: 79 9.9hp Johnson Seahorse Problems

Thanks for the replies. I replaced the spark plugs tonight and although it ran a little smoother at low idle it didnt effect the amount of time before the engine quit.

In the driveway it ran for two minutes and died. I choked the motor once and then on the second pull it ran for a little over a minute. It would run for one to two minutes after choking it and then pulling a second time.

When my neighbor squeezed the bulb every five seconds, we were able to keep the engine going for almost ten minutes. We started it back up immediately and were able to keep it going for another five minutes.

We also found that the gas can (an old metal kind) was being vacuumed shut where we had the lid unscrewed for the vent. Unfortunately this did not seem to be the main problem because holding it open didnt help.

Should I start by testing out a newer style of gas can? My neighbor said he would mix the fuel with some fuel line cleaner and try that before rebuilding the carburator. Is that good advice? If I do end up rebuilding the carburator what kit do I need for this motor? Is there a possibility that something is wrong with my fuel pump or filter? If there is does anyone know what kits I would need for that? Thanks again for the replies.
 
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Pleaselunkers

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Re: 79 9.9hp Johnson Seahorse Problems

I forgot to add that the coils barely even feel warm to the touch. My neighbor has experience with motors, though not two stroke engines. He doubted that the coils are the problem.

His guess is that something is wrong with the carburator, specifically the needle getting stuck. Again his advice was to run some fuel cleaner through it because of all the parts I would have to dissasemble to even get to the carburator.
 
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UncleBuck81

Seaman Apprentice
Joined
Apr 22, 2008
Messages
40
Re: 79 9.9hp Johnson Seahorse Problems

The same thing happened to me with a 78' 15HP(pretty much the same thing), took apart the carb, couple cans of carb cleaner later runs like a champ. Good Luck
 
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Xcusme

Commander
Joined
Apr 21, 2003
Messages
2,888
Re: 79 9.9hp Johnson Seahorse Problems

jrhenry24 said:
Thanks for the replies. I replaced the spark plugs tonight and although it ran a little smoother at low idle it didnt effect the amount of time before the engine quit.

In the driveway it ran for two minutes and died. I choked the motor once and then on the second pull it ran for a little over a minute. It would run for one to two minutes after choking it and then pulling a second time.

When my neighbor squeezed the bulb every five seconds, we were able to keep the engine going for almost ten minutes. We started it back up immediately and were able to keep it going for another five minutes.

We also found that the gas can (an old metal kind) was being vacuumed shut where we had the lid unscrewed for the vent. Unfortunately this did not seem to be the main problem because holding it open didnt help.

Should I start by testing out a newer style of gas can? My neighbor said he would mix the fuel with some fuel line cleaner and try that before rebuilding the carburator. Is that good advice? If I do end up rebuilding the carburator what kit do I need for this motor? Is there a possibility that something is wrong with my fuel pump or filter? If there is does anyone know what kits I would need for that? Thanks again for the replies.[/quote ]

If the motor runs when you pump the primer bulb, it points to a faulty fuel pump. Manually squeezing the bulb bypasses the fuel pump and sends fuel to the carb. You can test the pump. Remove the fuel line from the carb and place the end in a can. Rope the motor over and you should see fuel being pumped into the can. Adding a fuel cleaner to the fuel usually won't get it done. Removal of the carb and cleaning the carb cleaner, followed with compressed air is the only sure way. Install a carb rebuild kit, which includes gaskets, and float valve etc. If your fuel tank is in question, new plastic tanks are cheap, replace the fuel line hose and primer bulb too. If this is a new to you motor, be sure to replace the water pump impeller and thermostat too.
Click to expand...
 
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Pleaselunkers

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May 7, 2008
Messages
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Re: 79 9.9hp Johnson Seahorse Problems

Thanks for the help! I got a fuel pump, carb rebuild kit, thermostat, and impeller from iboats today. I put in the new fuel pump with a new clear fuel line to the carb and my boat is up and running. And its not stopping anymore! Once the service manual I ordered arrives I'm going to tackle the impeller and the thermostat like was suggested. I probably will wait until winter to rebuild the carb. How important is it that I replace the thermostat and impeller if they possibly have never been replaced before?
 
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