WOT question

[lyncraft_mechanic]

I have a 2002 40hp johnson outboard with a 11 3/4 x 17 prop on a 14' boat and i can only get about 25mph!!! i do not think the motor is running at top performance and have noticed that it seems to skip so today i installed a tachometer and found my maxium rpms to be only about 3000rpm WOT but i am told that this engine should be operating about 5500rpm WOT. does this sound correct? any suggestions for a fix????

 

[Silvertip]

Re: WOT question

On a 14 foot boat with a 17P prop that engine should easily spin up to 5800 RPM. Have you looked at the spark plugs? If not, do so -- they tell you alot about what's happening. Wet & black = weak no spark. Tan = running ok. Does the warning horn chirp when you turn the key on? The reason I ask is the engine may be overheating and going into SLOW mode which is a safety feature that allows the engine to run at about 2800 rpm during an overheat condition so you can get back to the dock without ruining the engine. That system also some oil related alarms associated with it. If that warning system is not working, you may not know the engine is overheating due to stuck thermostat, bypass valve, etc. Is the oil tank at least half full of oil? When the engine acts up, push in on the key or squeeze the primer bulb a couple times. If the engine picks up you have a fuel delivery problem. So do some checking and get back to us. As it is you've given us nothing to work with.

 

[lyncraft_mechanic]

Re: WOT question

I just pulled both plugs and they are black and wet. my warning horn does chirp when the key is turned on. i just filled my oil tank, could it be getting too much oil because i do run a little extra oil in my gas? i am going to try a set of new plugs in the morning and some fresh gas without any extra oil.
what else should i try?

 

[Silvertip]

Re: WOT question

Wet and black indicates very rich fuel mixture. You haven't messed with the little red lever on the primer solenoid have you? You also need to fix the warning horn. That system alerts you to overheat, low oil, no oil, and fuel restriction. Without it you have no idea what's going on with the engine. Are you the original owner of this engine? If not, I suspect the original owner disconnected the warning horn. After the engine has run awhile, place your finger on the cylinder head just above the top plug. If you can't hold it there more than 10 or 15 seconds the engine is over heating. But fouled plugs certainly will make it run poorly.

 

[lyncraft_mechanic]

Re: WOT question

The fresh gas and new plugs stopped the engine from skipping but had no effect on the RPM I am still 4000 RPM WOT on the warmup and 3000RPM WOT in gear. I am a little confused about the warning horn, should i be hearing the one beap from the system check when the key is first turned on, if not does this suggest that the warning system is not working? I run the engine on the pond this morning for about 45 minutes and do not suspect it to be overheating!!! what else should i be looking for? perhaps a new coil or the timing is off, I don't know any suggestions??????????????

 

[waterboy30]

Re: WOT question

Hello, I'm having the same problem with mine, it is wot at 4000 and takes forever to plane out..Gps says it runs about 30 mph wot,,,I have a 1980 40 hp johnson on mine...My plugs are wet and black after running and today I found a wire that is not hooked up to anything but has power running through it and I can't find out where it goes, I don't have a manual yet so it is hard for me to tell....Send me an email and we can try and brainstorm on our motors together....

Tony
waterboy22396@aol.com

 

[Cricket Too]

Re: WOT question

You said your warning horn is chirping when you turn the key on, so at least you know your horn is working.

Don't rev the engine over 2000 in neutral, not doing any good for anything, and will eventually do harm.

If you keep running it around without figuring out why it's not running right, your gonna hurt it, you ar luggin it badly right now and need to fix it, before contunuing running.

What kind of temp is the head after idling for 10 minutes or so? Can you keep your fingers on the head for 5 or 6 seconds?