1981 115hp johnson low revs WOT

[y not]

checked plugs & leads for spark all 4 ok compression 127 to 130 over all 4 cyl.<br />was working fine then hit bow wave of another boat then no pickup. still revs to 4500 but sluggish till on plane. almost like linkages not opening things fully?? IS THIS A 2 STAGE THROTTLE LIKE I IMAGINE?<br />any suggestions?

 

[Hooty]

Re: 1981 115hp johnson low revs WOT

It sounds to me like you've got a cylinder that's not working but you say it still revs to 4500. Has this always been wot?<br /><br />c/6<br />Hooty

 

[y not]

Re: 1981 115hp johnson low revs WOT

thanks for the reply hooty.<br /><br />No full open throttle has previously been 5,300 rpm throwing a 17 inch pitch prop

 

[Forkin' Crazy]

Re: 1981 115hp johnson low revs WOT

The the timing starts moving first, then the carbs are operated by the roller when the arm contacts it. Put it in gear (rolling the prop as you do) and wide open throttle. With the air box lid off all the blades should be horizontal. I don't think that's the problem though.....If you do this run it like this and check for a bad reed. It will blow fuel/air back out of the carb throat.<br /><br />You may have a clogged main jet in one of the carbs. What do the plugs look like? Check the spark at 7/16" gap on a tester. You can run it at night to check for spark leaks too.<br /><br />fuel+compression+goodspark=run<br /><br />Is it spring there?

 

[Sherman]

Re: 1981 115hp johnson low revs WOT

I had a similar problem with the same engine. I would check very carefully that the spark plug wires are not grounding on the cover hold down brackets at the back of the motor. My problem only occured with with the motor cover in place.

 

[Hooty]

Re: 1981 115hp johnson low revs WOT

Ok, sounds like one cylinder isn't making power. With the engine idling, ground sparkwires, one at a time and see if you can find the one not hitting.<br /><br />c/6<br />Hooty

 

[y not]

Re: 1981 115hp johnson low revs WOT

ok will check spark and get back to you all when I have. thanks for advice.<br /><br />No, Forkin Crazy is glorious SUMMER!!!! yet another glorious day in paradise.

 

[y not]

Re: 1981 115hp johnson low revs WOT

Ok just checked spark again, this time missing on one cylinder. Traced fault to poor connection on terminal in lead.<br /><br />Thanks for all the help