1989 Johnson 15HP

Hey guys, I bought my first small jon boat and motor last week. The Motor (1989 15 HP Jonson) runs excellent and was pushing the boat along very well but could not get the boat (Alumacraft 1436) to plane. I got back to the ramp to load up and realized that the motor was locked into the position offering the most tilt away from the transom. Would this have kept the boat from planing? It was very close to being on plane with My brother and I, but, when using it by myself the nose of the boat was extremely high in the water.

Yes very much so, The best way to play in a boat out is that have the motor took close to the transom as you can get it. If you do not have trim and tilt you have a pen bar on the bottom of the transom bracket it usually has 5 to 7 holes in it pull the pin out and move it all the way to the father setting in toward the transom. But for actual good runit would probably need to be in the two are third hole out from the transom


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exactly what I needed to read.

Play around with it. It will often need to be in a different hole for different loads. PS Don't drop the pin!

I have a similar combination of boat and motor (1985 15hp Johnson and a 1436 Lowe Jon) it will plane two big guys and gear easily. The total weight not including the boat is about 600#. Add a third guy and it struggles and it's over recommended weight limit.

If I'm by myself I have to move all the loose weight up front and add some ballast. If the front is to high, it's not going anywhere. I run the motor in the trim hole closest to the transom. Which in my case puts the angle of cav plate just slightly off the bottom of the hull as to bring the bow down. I tried moving it out one hole, this leveled the motor with the hull, but it ran a little better with a slight angle.




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So, I decided to take my rig out on Friday an could not get my motor to run above idle more than 100'. It would start first pull and idle fine for as long as needed but as soon as you'd advance the throttle it would bog down and stall out. After doing this process a few times the motor would not start unless you sprayed fuel into the breather. I also realized that the primer bulb had gone soft and would not fill up with fuel. Since this happened I went ahead and ordered a carb kit, new fuel pump, spark plugs, and replaced my old and tank to motor lines with brand new ones today. Any idea what could have caused this? The only odd thing I noticed was fuel had seeped out from the choke during transit.

My guess would be a bad fuel pump. Not sure what to think of the fuel from the choke


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The primer bulb goes soft once you start the motor, not a problem far as I know.

I have found the website Leroy's Ramblings a treasure trove of information on these OEM motors, especially the 9.9 / 15 Hp.

Keep us posted as you get it sorted out.


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Thanks as always guys! Pertaining to the original bulb, after it stalled the final time it never would fill up again. I tried a replacement as well and it would not fill up. If changing the parts doesn't help I'll address the fuel lines and check compression. The motor worked great the first time I used it (which was for hours).

Pappy said:

The primer bulb should pull fuel easily when hand pumped and get firm feeling when the carb bowl is full and the needle has closed against the seat inside the carb. There are check valves inside the primer bulb itself. To aid with these valves closing it helps to point the arrow on the bulb straight up when pumping. This should help.
Before going through with everything you ordered try running your engine and hand pumping the bulb to see if the engine will run past idle. You will be by-passing the fuel pump when you do this and is a good way to check fuel pump operation vs a carb issue. If the engine runs to WOT the fuel pump has failed. If not you have a carb issue.

Click to expand...

Tried all of this with the same result (could not get it running without spraying fuel into the breather on the carb)

I pulled the fuel line that goes from pump to carb and saw that fuel would pump from the line when squeezing the bulb, but, the bulb would not firm up.

The fuel pump is making noise when the motor's running. I'm assuming its good.

The fuel pump is original to the motor and was going to be replaced for peace of mind, and I'm 99% sure the carb has not had any work done.

I'm hoping replacing some minor parts will fix it up.

Fuel pump was the issue. New one arrived today and was swapped out in 2 minutes. Runs like a top once again.

Good it's fixed. Sometimes a closed vent on the tank will make them act janky.

[emoji106]


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Great!!! Also unless running in deep water never lock your motorvlatch down!! If you hit stump etc. It will break the cavitations plate and cost you$$$$$$==!!!! Done it myself very expensive repairs!!

I come from a kayak fishing background and have used various trolling motors on my SOT's for years. I'm very familiar with the tip about locking down a motor. I also found out the hard way lol.

Well, I was incorrect. Motor is still not running up to snuff. I had been testing it on the water hose and it ran great for hours. I decided to take it out Sunday and it started up and ran in neutral 100%. Went to put it into gear and it stalled out. Figured out that I could get it to go by playing with the choke & it ran perfect when above 1/2 way on the throttle. Got home and popped off the silencer once again and remembered that it was packed with blue mattress pad when I cleaned the carb. Got researching why and found out that it was very common to have a cracked carb cover on this model. I took a bright light to it and sure enough it has a hairline crack from the needle valve all the way to the rear screw. I'm assuming this is my issue. New cover has been ordered. Time will tale.