15hp bog and die in forward gear only

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TOY BOAT

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Dover, NH
I have a 1994 Johnson 15 horse manual start, manual choke tiller. I sent the motor to a reputable shop and asked them to ix anything they found wrong. The motor would not low idle. They rebuilt the carb, and said that was the only issue they could find. I replaced the lower end oil and water pump. With muffs on, it started fine, idled great, went into forward, and reverse fine. Got it to the lake yesterday, and it started fine, went into reverse ok, but then when I put it into forward it died. This kept happening. Finally I pulled the cover, and opened the fuel pump to check the screen. It was clear. Pulled both plugs to see if it was flooding. Finally I found the upper ignition plug wire was broken. I fixed that, and figured that was the issue. Seemed better after that, but then continued to do it the rest of the day. I had to rev up the motor, and put it in gear. At idle it would just not go into forward without dying. Once going, it was fine. Got it up to 18 mph at one point. I have ordered new plug wires, but it is weird that in reverse the motor goes fine at idle, but not forward. Any ideas or does it sound like a ignition issue that new wires should fix?
 
Sounds to me like the slow speed idles screw is not set properly. I don't have time to write it out but check this site out I believe he has a good walk through on how to do it. Your slow speed idle screw is on top left of carb I think on a 94'.........Have to have boat in water to do this correctly. And just because it is a reputable shop does not mean they are good....seen this many times before unfortunately

https://www.leeroysramblings.com/Johnson_9.9_carb-fuel_pump.htm
 
Thank you Johny25. Any help would be great. I looked over the link you posted, and like you said it sounds like I need to make adjustments in the water. But I am not sure what I am doing. There seems to be a lot of adjustments to fine tune the motor. I feel like I need a marine tech with me. lol

I see the little screw you mentioned at the top that is at a 30 degree angle behind the air box. Am I supposed to remove the cover, remove the air box, and adjust while in the water? I guess I am a bit confused. You would think a adjustment that needs to be made in the water would be more accessible.
 
No marine tech needed....believe in yourself :)

Ok lets try and get you a better idea of how to do this. Your slow speed idle knob is #15 in parts diagram here https://www.boats.net/parts/search/BRP/JOHNSON/1994/J15EERE/CARBURETOR/parts.html

Ok we can get it close in the driveway on muffs or in a barrel before you get it on the lake. Remove cover or what ever to get to the slow speed idle screw. Then turn it all the way in until it bottoms out (lightly seating it, do not turn to hard). Then back it out 1 and a half turns. This is a good starting point. Now start engine and keep it in neutral during this phase. After it is warm turn throttle all the way down. Now turn screw a quarter turn out or left and wait 30 seconds until engine catches up. What we are trying to do is get the engine to idle higher. Keep doing quarter turns (waiting 30 secs each time for engine to catch up) until you find the highest idle, then turn it back a quarter turn. Now we are ready to do it on the lake in gear.

So now we are hoping that it will go into gear without dying. If it dies then we need to look elsewhere but I suspect this may be your issue. So if it goes into forward gear then we can do final slow speed set. Get motor warm, in forward gear and throttle all the way down at its slowest speed. Turn screw either direction (usually out or left) in quarter turns waiting 30 seconds just like before to find highest idle.( When you go to far engine will sputter and start to die but you will notice this in driveway also). So now that you found highest idle turn it back a quarter turn. All done :D

We can also set the engine RPM idle on the throttle grip too if it needs it but lets get this done first. If you have any questions regarding the procedure just ask. The only stupid question is the one not asked
 
Thank you Johny25. That clears up a lot. I was looking at the screw marked #1. It is the one I thought you meant. Your explanation seems very simple. I am going to try it.
Pertaining to the adjuster on the end of the tiller handle. Where should I set that before getting started? I understand it is the final adjustment if needed. The first link you posted mentioned turning it in til it is almost off the threads, then turning it out one full turn. Is that a good place to start before making the other adjustments?
 
Well I set mine while my tachometer on the engine so I can get it to spec. I believe you want the RPM to be around 675 rpm give or take 50 rpm. But if it sounds like it has a decent idle right now (not reving real high or real low) I wouldn't worry about it until you find of if the slow speed idle corrects the first problem.
 
It has been some time since I last posted. The weather has not been on our side, or we have been busy with other things. So anyways, I had taken Johny25's advice, and turned the mixture screw one quarter turn with it in a barrel. Once I did that, the motor would shift into gear without stall every time. Yesterday we had it out at the lake, and it was absolutely flawless.

Not sure what all the decking and gear ad to the factory base weight of 275 lbs, but with my wife and I the little 15 horse managed 20 mph all day at full throttle.

Thank you Johny25 for the useful information. It made life very easy out on the water so we could concentrate on a nice day.
 
Played with the carb a little more, and moved the pin up that adjusts the trim from the second hole from the transom to the third hole and we saw 23 mph last night. Motor is moving 700+lbs so I think that is great.
 
[url=https://www.tinboats.net/forum/viewtopic.php?p=321463#p321463 said:
TOY BOAT » Today, 11:55[/url]"]Played with the carb a little more, and moved the pin up that adjusts the trim from the second hole from the transom to the third hole and we saw 23 mph last night. Motor is moving 700+lbs so I think that is great.


how are you getting your mph readings? gps?
 
[url=https://www.tinboats.net/forum/viewtopic.php?p=321463#p321463 said:
TOY BOAT » Sun Jul 07, 2013 12:55 pm[/url]"]Played with the carb a little more, and moved the pin up that adjusts the trim from the second hole from the transom to the third hole and we saw 23 mph last night. Motor is moving 700+lbs so I think that is great.

If that 23 is GPS I wouldn't adjust any further.....that's flying for a 15hp on a 14ft with 2 people in it.
 
[url=https://www.tinboats.net/forum/viewtopic.php?p=321491#p321491 said:
MDCrappie » 07 Jul 2013, 17:52[/url]"]
[url=https://www.tinboats.net/forum/viewtopic.php?p=321463#p321463 said:
TOY BOAT » Sun Jul 07, 2013 12:55 pm[/url]"]Played with the carb a little more, and moved the pin up that adjusts the trim from the second hole from the transom to the third hole and we saw 23 mph last night. Motor is moving 700+lbs so I think that is great.

If that 23 is GPS I wouldn't adjust any further.....that's flying for a 15hp on a 14ft with 2 people in it.
GPS and the speedo on the fish finder. Both show the same.
 
[url=https://www.tinboats.net/forum/viewtopic.php?p=321463#p321463 said:
TOY BOAT » 07 Jul 2013, 11:55[/url]"]Played with the carb a little more, and moved the pin up that adjusts the trim from the second hole from the transom to the third hole and we saw 23 mph last night. Motor is moving 700+lbs so I think that is great.


I almost don't believe a 15 can push that weight at that speed but if u say so I believe ya! that's scootin for a 15hp!!!
 
That is fllying for a 15. =D> Mine will do 19mph in the 14' . I wouldn't touch a thing on that motor =D> What pitch prop ya running ?
 
[url=https://www.tinboats.net/forum/viewtopic.php?p=317274#p317274 said:
Johny25 » 04 Jun 2013, 00:10[/url]"]No marine tech needed....believe in yourself :)

Ok lets try and get you a better idea of how to do this. Your slow speed idle knob is #15 in parts diagram here https://www.boats.net/parts/search/BRP/JOHNSON/1994/J15EERE/CARBURETOR/parts.html

Ok we can get it close in the driveway on muffs or in a barrel before you get it on the lake. Remove cover or what ever to get to the slow speed idle screw. Then turn it all the way in until it bottoms out (lightly seating it, do not turn to hard). Then back it out 1 and a half turns. This is a good starting point. Now start engine and keep it in neutral during this phase. After it is warm turn throttle all the way down. Now turn screw a quarter turn out or left and wait 30 seconds until engine catches up. What we are trying to do is get the engine to idle higher. Keep doing quarter turns (waiting 30 secs each time for engine to catch up) until you find the highest idle, then turn it back a quarter turn. Now we are ready to do it on the lake in gear.

So now we are hoping that it will go into gear without dying. If it dies then we need to look elsewhere but I suspect this may be your issue. So if it goes into forward gear then we can do final slow speed set. Get motor warm, in forward gear and throttle all the way down at its slowest speed. Turn screw either direction (usually out or left) in quarter turns waiting 30 seconds just like before to find highest idle.( When you go to far engine will sputter and start to die but you will notice this in driveway also). So now that you found highest idle turn it back a quarter turn. All done :D

We can also set the engine RPM idle on the throttle grip too if it needs it but lets get this done first. If you have any questions regarding the procedure just ask. The only stupid question is the one not asked



This one, but one of many, of examples of the great worth of the TINBOATS site. Johny25 and others have great knowledge, and willingness to help another guy out, just because that's the type of people they are.

I feel lucky to have stumbled on TinBoats last year, and that feeling is renewed each time I see examples of good people doing good things for one another.

=D>
 
As the others have stated......23mph in a 14' tin with a 15hp is smokin fast. Not to say it can't be done but those are phenomenal numbers if you have more than one person in the boat.

2.41:1 gear case 11 pitch prop at 6000+rpm it is plausible to see 23mph......don't expect anymore out of her though and don't mess with anything lol
 
Video popped up when I was searching other motors......this is a 15hp flying.....

https://www.youtube.com/watch?v=z5k-CRH4_CM

little slow out of the hole, but once it's up......
 

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