1981 Johnson 7.5hp sluggish

[Perry125]

Hi, I have a 1981 7.5 on a 12ft aluminum V jon boat.

The motor will only get the boat to around jogging speed. I think it should do more.

It runs fine, starts easily, and idles. The throttle linkage is working correctly.

Apparently there is no high speed adjustment, so should i just clean the carb out?

Thanks

 

[Perry125]

Re: 1981 Johnson 7.5hp sluggish

Also i should note the passenger load was around 300 lbs. Is this all it's going to do? Jogging speed?

 

[raczekp1]

Re: 1981 Johnson 7.5hp sluggish

look at You tube,ther is plenty videos showing this model with boats and compare.

i think the problem can be with firng on one cylinder.
take out spark cower from one spark and look if will die.put back.and take cover from secend spark plug and look if changes

 

[Perry125]

Re: 1981 Johnson 7.5hp sluggish

Apparently it should be going 15+mph. Im only getting half that.

It's not misfiring or running on one cylinder, and i just changed the plugs.

I thought it could be the prop is the wrong size, its about 3-4".

Anyone know what this could be?

 

[Jon Boat Jim]

Re: 1981 Johnson 7.5hp sluggish

I think that someone has put a small prop on the motor!
My 1982 7.5 HP pushes my 12 foot Jon Boat ~ 14 mph per my GPS. With two on board ~ 11 mph. It has a three-bladed prop. Each lobe measures about 4.5 inches from center of hub to edge of lobe.