Johnson 70 2 stroke only reaching 3500 rpms at WOT

[Jimmyb617]

Boat starts and takes off fine just won't go over 3500 rpms. Carbs are fully opens at WOT, good spark, good compression, tried a new power pack and that wasn't it. Prop is the correct size according to marine shops around my area. No idea what do to nex, buddy says it maybe the stator but I'm not sure how to test it while in the motor I have a multimeter. Please help. Motor is on a 17 ft. Wellcraft

 

[Jimmyb617]

Also installed new spark plugs and wires

 

[jakedaawg]

compression and spark test.

 

[Jimmyb617]

Tested both, good spark on all cylinders and 150 compression in each

 

[flyingscott]

Are the carbs opening all the way? Is the timer base moving smoothly?

 

[Jimmyb617]

Are the carbs opening all the way? Is the timer base moving smoothly?

Yes the flaps(not sure what they're called) are perfectly horizontal at wide open throttle it. Someone had asked me about the timer face and I am not sure exactly what to look at. Under the flywheel there is something that moves back and forth when I move the throttle and it moves until it hits a stop screw

 

[mrcj001]

Check the WOT adjustment (the screw above the idle adjustment screw) sometimes folks get these mixed up.

 

[flyingscott]

If the carbs are opening to 90 deg in the carb body don't touch the throttle stop.

 

[Jimmyb617]

Okay gotcha. If the carbs are opened up is there anything else that needs to happen wth the linkage or anything for it to be WOT, just making sure it's not somthing with ge throttle cables or anything

 

[flyingscott]

The timer base is under the flywheel and moves with the throttle until it hits the stop under the flywheel.

 

[Jimmyb617]

I checked the timer bass it moves when I throttle it up but stops at the stop screw only at about half throttle then from half throttle to full throttle it doesn't move. Is t suppose to move all the way until full throttle?

 

[flyingscott]

That is operating correctly the max timing is all in at about 3500 rpm so it stops sooner than the carbs will. Go to www.cdielectronics.com and look at the troubleshooting guide they offer for your ignition.

 

[jakedaawg]

Has this boat ever run well that you "personally" witnessed?

What size prop do you have on there? A 70 on a 17 ft wellcraft is horribly under powered. I would expect about a 11 or 13p.

How old is the boat? Has it lived outside? Boats get waterlogged. They can look beautiful but weigh an extra grand or so. There is no way to get the water out of the foam.

If the carbs have been cleaned, its got compression and spark, and nobody messed with the linkage then its something else in or on the boat.

Have you checked Max timing?

 

[jakedaawg]

From the pack to the coils are three orange wires. What color stripe goes to which coil?

Gonna need to do a cylinder dropntest on this probably. While running in gear under load pull plug wire off with plastic pliers. Note which cylinders don't have an effect.

 

[Jimmyb617]

Has this boat ever run well that you "personally" witnessed?

What size prop do you have on there? A 70 on a 17 ft wellcraft is horribly under powered. I would expect about a 11 or 13p.

How old is the boat? Has it lived outside? Boats get waterlogged. They can look beautiful but weigh an extra grand or so. There is no way to get the water out of the foam.

If the carbs have been cleaned, its got compression and spark, and nobody messed with the linkage then its something else in or on the boat.

Have you checked Max timing?

Damn I've actually never really thought about that. I figured a 70 would be decent. The boat is a 1980 wellcraft and it has been stored outside. I've had it for 3 years and last year the motor overheated because of a clogged thermostat. It was a 115 and pushed it about 38. I bought this Motor from a guy and installed it and it never has got over 3500 on this boat

 

[Jimmyb617]

Just checked the prop on it right now is a 13 3/4 x 15. What do you think if I try an 11 degree pitch? I've heard the lower the pitch the higher rpms right?

 

[jakedaawg]

Do post 14 1st

 

[Jimmyb617]

14 degree?

 

[jakedaawg]

14 degree?

Well, I meant do post #14 first.

If your max WOT timing is only 14 degrees that is part of the issue but at 3500 rpm isn't that far off.

 

[Jimmyb617]

Ohhh okay didn't know they were numbered lol. Is there a way to test the max WOT timing?