15hp wont run unless I keep fooling with choke

[northshoremb]

I just had my 1980 15hp Evy tunned up buy dealership 2 weeks ago and it ran perfect except it would load up when trolling then wanna stall. I went fishing and all I did is throw into neutral and rev it then back to trolling for a minute. Then few days ago I went out and it would totally die if I even tried to go less then 1/2 throttle. You would need to pull it over a few times and rev the **** out of it. I went home and mixed up some gas with a 75:1 ratio with fully synthetic to see if for some reason the 50:1 was the issue. I went out and the motor ran the same way and sometimes ran on 1 plug at 1/4 throttle and needed to crack it to clear it up and run on 2. Took it out of water and put on the muffs and changed to NGK BR7HS with .030 gap like some people said. Still it runs like **** and need to fool with choke in and out even at full throttle and won't even wanna run at 1/2 or less even with choke closed or open.

Anyone have any idea what the BLEEP is going on???? Can it be a coil or something? I am losing my mind cause it for sure run good with 75:1 and properly gapped plugs. Would for some reason have something gotten into the carb and jammed it? Is it hard to take apart carb to check?

 

[wilde1j]

Re: 15hp wont run unless I keep fooling with choke

75:1 is a bad idea as are NGK plugs and revving the **** out of it, unless you're hoping to have a 15HP paperweight.

Having to use the choke for normal operation suggests running too lean, carbs crapped up, etc., but it's hard to believe all this happened in two weeks since you got the motor back from a dealer. Change back to Champion plugs and proper gas mixture. I would let the dealer have a look at it before doing anything rash.

 

[northshoremb]

Re: 15hp wont run unless I keep fooling with choke

I did put champion plugs back in and run the 50:1 from my other tank with no F'n difference. I take the plugs out and they sure arn't running lean. **** full of gas and still looking new with no signs of brown/tan. It absolutely isn't running lean by no means.

 

[ondarvr]

Re: 15hp wont run unless I keep fooling with choke

I did put champion plugs back in and run the 50:1 from my other tank with no F'n difference. I take the plugs out and they sure arn't running lean. **** full of gas and still looking new with no signs of brown/tan. It absolutely isn't running lean by no means.

Fact is its running lean, only reason for it running better with the choke on.

A clean carb yesterday means nothing today. If it ran OK at any time after you got back, then they most likely did a good job, but there may have been something (gunk) in the carb they missed and broke loose and got stuck in the low speed jet.

Does yours have a low speed adjustment knob on the front of the motor?

 

[northshoremb]

Re: 15hp wont run unless I keep fooling with choke

Yes there is a low speed knob but doesnt make a difference. Im not say that it runs perfect with choke on. It won't idle what so ever or even run at 1/4 throttle with choke in or out. If I start it then open it up to 3/4 or full throttle I need to open choke then close shoke then open choke to keep it running. If its all the way closed it wont work if its half open it wont work or if its fully open wont work it must be adjusted once the rpms start to drop. If you are saying its running lean then how could I run wide open for 4 kms yesterday and not seize up???? But when I cut the throttle down to 1/4 or less it stalls???

 

[wilde1j]

Re: 15hp wont run unless I keep fooling with choke

Are you saying you ran it for 4 KM with the choke "OFF"?

 

[kenmyfam]

Re: 15hp wont run unless I keep fooling with choke

50 to 1 mix
Change back and stay with Champion plugs.
Service the carbs.
Is the tank vent open ??

 

[tx1961whaler]

Re: 15hp wont run unless I keep fooling with choke

Yes there is a low speed knob but doesnt make a difference. Im not say that it runs perfect with choke on. It won't idle what so ever or even run at 1/4 throttle with choke in or out. If I start it then open it up to 3/4 or full throttle I need to open choke then close shoke then open choke to keep it running. If its all the way closed it wont work if its half open it wont work or if its fully open wont work it must be adjusted once the rpms start to drop. If you are saying its running lean then how could I run wide open for 4 kms yesterday and not seize up???? But when I cut the throttle down to 1/4 or less it stalls???

Don't get your fuel/air "lean" mixed up with the gasil ratio "lean". Two different things. The carb regulates the fuel/air mix going into the motor. If that is "lean" then too much air is going into the motor. If there is too little oil mixed into the gas, that is also called "lean", but means something different. If it runs better with the choke on, the mix knob does nothing, and if it does not run any better when the fuel bulb is squeezed, that points to a clogged up carb.

 

[northshoremb]

Re: 15hp wont run unless I keep fooling with choke

Yes it ran 4km with the choke off and I was doing avg 19mph on GPS, but when I stopped to troll it kept loading up and stalling. Took 3-4 pulls to start then needed to open throttle to clear the foul plug cause it would run on one then clean up and run on 2. Then try and troll again and in 10 seconds do same thing. Said F that I am just gonna go home so give her the throttle and ran wide open no problem back 2km to marina where when I slowed down for no wake sign she started to run like **** again (this is all happening with the Champion QL77JC4 plugs the dealer put in it and a 50:1 gas mix) Thats when I came on here ready that the QL77JC4 plugs suck and I bought the NGK BR7HS and tryied out a Fully synthetic 75:1 ratio that might help with trolling. I wasnt planning on using 75:1 for WOT but carry it as a second gas can just for trolling and hook up to the 50:1 for WOT. But that doesnt seem to help. It must be the carb but I just spent $160 at dealership for the tuneup and ran ok for the first to trips out fishing.

 

[northshoremb]

Re: 15hp wont run unless I keep fooling with choke

Don't get your fuel/air "lean" mixed up with the gasil ratio "lean". Two different things. The carb regulates the fuel/air mix going into the motor. If that is "lean" then too much air is going into the motor. If there is too little oil mixed into the gas, that is also called "lean", but means something different. If it runs better with the choke on, the mix knob does nothing, and if it does not run any better when the fuel bulb is squeezed, that points to a clogged up carb.

Now I think I see what you were calling lean. You didnt mean lean as in burning down do to to little premix but you mean lean as in not getting enough gas and to much air?? So can I pop the Mixture knob off and then turn it and put it back on to reset it to a richer setting?? I mean if its set to rich right now and still isnt getting enough gas then could I turn it all the way to rich pull out knob and push it back in in the all the way lean setting?? That way it gives me one more to richer do to the resetting of the knob?

 

[ondarvr]

Re: 15hp wont run unless I keep fooling with choke

High speed and low speed circuits in the carb only operate with a slight overlap, so it can run well in one range and terrible in the other. So running wide open without a problem is normal and so is the other way around.

You never really said what you needed to do with the choke to make it run right, but if you need to use it at all, it means its running too lean in that RPM range.

If you adjust the low speed knob and it does nothing, then that circuit is clogged. Sometimes by turning it all the way in and then all most all of the way out, it may let the debris past the needle. To start with, turn it all the way in until it seats lightly, don?t crank it down. Count the exact number turns so you can return it to that setting before you try to start it again. If that doesn?t do it, it needs to be cleaned again.

 

[northshoremb]

Re: 15hp wont run unless I keep fooling with choke

High speed and low speed circuits in the carb only operate with a slight overlap, so it can run well in one range and terrible in the other. So running wide open without a problem is normal and so is the other way around.

You never really said what you needed to do with the choke to make it run right, but if you need to use it at all, it means its running too lean in that RPM range.

If you adjust the low speed knob and it does nothing, then that circuit is clogged. Sometimes by turning it all the way in and then all most all of the way out, it may let the debris past the needle. To start with, turn it all the way in until it seats lightly, don?t crank it down. Count the exact number turns so you can return it to that setting before you try to start it again. If that doesn?t do it, it needs to be cleaned again.

I did mention what had to be done with choke (The choke has to be kept moving in and out like a primer and when you here the motor start to die move her in or out to get the revs back up) Also what do you mean COUNT THE TURNS it takes to turn the idle mixture knob????? It only is made to do about a 330 degree turn from lean to rich. Are you saying that it should keep turning? The dealer is 45minutes away and guess I will just need to bring it back in. Thought that it would be easier just to ask and save myself hour and half driving time.

 

[Rick.]

Re: 15hp wont run unless I keep fooling with choke

When setting the slow speed needle initially you pull the plastic knob off so nothing limits the tuning of the needle. Count the number of turns clockwise until it is lightly seated so that you have a reference point of where it was when you started. Once your happy with the setting you put the plastic knob back on in the mid position and leave it there. Rick.

 

[northshoremb]

Re: 15hp wont run unless I keep fooling with choke

When setting the slow speed needle initially you pull the plastic knob off so nothing limits the tuning of the needle. Count the number of turns clockwise until it is lightly seated so that you have a reference point of where it was when you started. Once your happy with the setting you put the plastic knob back on in the mid position and leave it there. Rick.

Thats what I was thinking it is just like the air screw on any snowmachine or dirtbike just hooked up to a plastic knob. On avg how many turn out should it be? I know on sleds and bike its about 1-2 turns out. Or is every boat application different??

 

[Rick.]

Re: 15hp wont run unless I keep fooling with choke

Out about 1 1/2 turns from gently seated. Go the the top of this forum and look at the Top Secret File and look for the article on adjusting carbs. That whole TSF is packed with good information that may well help you get this beast running right. Here is another link that I see as a must read for all 9.9 and 15 owners. It will greatly increase your knowledge of the motor. They are great motors when they run right and they do run right most of the time. I have brought a few back to life and they are all running fine now with just a little bit of normal maintenance. Rick.

http://www.sschapterpsa.com/ramblings/OMC/OMC info.htm