won't run wide open

russrmartin

Recruit
Joined
Aug 11, 2003
Messages
5
I also have a problem getting my motor to run wide open when under a load. It will start, idle, and run to 3/4 throttle just fine, but when cracked wide open it dies off. Engine does not sound like it is missing, just acts almost exactly like 3/4 throttle is full, and full throttle is past full and on the way down again. I am very new to outboard engines, but this one was cheap and will be a good one to learn on. Any ideas on things to check will be appreciated. Also, the plugs after running full wide open, one is a nice honey colored, the other is a bit darker, and a little wet. I do mix my fuel a touch richer than what is recommended. Recommended 50 to 1, mixed about 60 to 1. Thanks in advance guys.<br /><br />Russ
 

Fouled Plug

Ensign
Joined
Jun 29, 2001
Messages
935
Re: won't run wide open

Check the throttle linkage at the carbs and see if the butterflies are fully open at WOT. If that looks OK, does pumping the primer bulb help?
 

jim dozier

Lieutenant Commander
Joined
Jan 8, 2003
Messages
1,970
Re: won't run wide open

Just to echo Fouled Plug, check the linkage on the carbs with the airbox off and verify that the butterflies are all the open (parallel with the air flow) at full throttle. Some linkages may not have a stop on them, and will allow the butterflies to open past full which in effect begins to close them. Your description sounds suspiciously like someone didn't do a link and sync properly, and at full throttle you are getting 3/4 throttle and at 3/4 throttle who knows what you are getting.
 

russrmartin

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Joined
Aug 11, 2003
Messages
5
Re: won't run wide open

Thanks guys. I did check these out, and the throttle linkage was loose where it attaches to the side of the carb. I tightened it down again, and took the ski out and it did much better. I do have 1 follow up question, mostly just theory I guess. I reinstalled an aftermarket exhaust pipe. The guy I bought the boat from said it had it on it and he took it off, and did not rejet the carb after taking it off, therefore, I should be able to put it back on without rejetting. I put it back on, and per instructions from a friend of mine, put new plugs in. I took the boat out, warmed it up for a couple of minutes, then opened it up all the way for a hundred yards, shut it off and coasted to shore. My friend says doing this and looking at the plugs will tell me whether I do need to mess with anything else. My question is, 1 plug looks white, as in looks to lean, the other is black, maybe a little too rich. I know there is some compression difference between the two. Am I correct in thinking it's best to richen the the high speed screw and just expect to foul a plug every now and again on the other, or are there any other things I can or should do. Thanks again guys.<br /><br />Russ
 

jim dozier

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Joined
Jan 8, 2003
Messages
1,970
Re: won't run wide open

What engine (year make model) do you have. Most outboards don't have an adjustable main (high speed) jet. If one cylinder is running lean its probably due to gum deposits in the carb and jet orifices requiring a complete rebuild. The black plug could be due to misfiring ignition or a stuck open float in the carb requiring a carb rebuild. The idle circuits are probably adjustable but they won't affect the high speed operation. I would not alter the fixed jets just clean them as part of a complete carb rebuild.<br /><br />Why did the previous owner remove the exhaust pipe? Most 2-strokes have tuned exhaust and they will run better with the pipe on than with it off.
 

russrmartin

Recruit
Joined
Aug 11, 2003
Messages
5
Re: won't run wide open

JIM,<br /><br />The machine in question is a 92 yamaha wr650q jet ski. I have only owned it a month. The previous owner bought the ski, and the aftermarket exhaust was on it. He then took it off and put the stock exhaust on. I am in the process of putting the aftermarket back on. I did check compression on both cylinders, and my previous info was incorrect. The compression on both sides was equal at 150, and I had a neighbor with a little more experience with 2 strokes look at the plugs. He informed me that they are fine. He also echoed you in that the difference between the plugs is probably just from a dirty carb, and suggested I clean it. Thanks again for the help with the throttle problem.
 
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