I'm at a loss

[denlou]

I have a 16 ft. Wellcraft Airslot that is now powered by a 1986 Johnson 150 (I know it's overpowered) running a 14 1/4 x 19 stainless prop.
The boat performs beautiful, but, when accelerating from 2800 rpm to wot it's like a rocket, It'll push you back in your seat, but 5000 rpm is as high as it will go.
I find it hard to believe I'm over propped with the incredible acceleration it has.
The carbs were rebuilt 3 wks. ago and all linkage adjustments were checked, compression is good and all the plugs are burning good.
The only thing I have not checked is the timing.
It's as if the motor has an rpm limiter, 5000 rpm comes up very quick, but that's it.
Any help would be appreciated, Thanks.

 

[chevinrude]

Re: I'm at a loss

you may want to drop down in pitch on that prop regardless. The 5000rpm with a 19 prop sounds right. You may want to drop down in pitch to a 17, that might help make up your lost rpm which at best is probably 5500.

 

[denlou]

Re: I'm at a loss

Oh, If I'm only losing 500 rpm I'll probably leave things as is.

Thanks for your reply.

 

[kenmyfam]

Re: I'm at a loss

Oh, If I'm only losing 500 rpm I'll probably leave things as is.

Thanks for your reply.

You could be "lugging" your motor at that RPM. Personally I would drop a couple of inches of pitch and see what happens. Always a good idea to have a spare prop anyway in case of unforeseen circumstances.

 

[denlou]

Re: I'm at a loss

I had no idea I would be lugging the motor at 5000 rpm.
What would the difference be if I were just out cruising at 3500- 4000 rpm. ?

Sorry, I just don't understand.

 

[kenmyfam]

Re: I'm at a loss

It's more what the load is compared to the RPM. I think you should be looking for around 5,500 RPM at WOT or thereabouts.
Not 100% on this though. Someone else will chime in with the actual soon I am sure.

 

[jonesg]

Re: I'm at a loss

I had no idea I would be lugging the motor at 5000 rpm.
What would the difference be if I were just out cruising at 3500- 4000 rpm. ?

Sorry, I just don't understand.

it is still lugging at lower speeds if it lugs at WOT.
Unless its a commercial which has different gearbox and is designed to run a bigger bat at lower rpm. Wish you guys would post your model number, it makes everything easier all around.

 

[denlou]

Re: I'm at a loss

J150tlcdc