No speed

[Holy Shamolee]

I have a 16 and a half foot grew boat.
It has a aq120b engine in it.
Volvo 270 leg
No lack of power.
I put it in gear, hit the throttle and it revs to 3500, or more rpm as if it wasn't even in gear. Bur it is.
It gets the boat up to about 15 miles an hour at 4000 rpms.
Prop measures out at 14 inches. Not sure of the pitch, its just not stamped into it anywhere.
Only thing stamped into it is Michigan SMC 268.
The gear ratio is 2.15 to 1
I see that stamped into the lower leg right behind the zinc.
Seeing as this model is called a grew speedboat, I am thinking something is amiss.
The bottom half of the leg seems a little different color from the top half.
It's only 16.5 FT..I'm thinking it should go like a bullet with that engine.
But I could be wrong. I have been before.
any Ideas?

Edit

 

[Scott Danforth]

first, are you sure the shift cable is working correctly giving you full throw?
second, are you sure the shift assembly at the drive is adjusted correctly
third, is your prop hub still intact or has it spun
4th, if you only get 4000 RPM's you probably are only running on 3 cylinders or less.

 

[Holy Shamolee]

I can get more than 4000, no problem.Just happened to be the number I stopped at.
Not to sure how to check the things you mentioned, but I did put it in forward and turned the prop. No slipage that i could tell. It was very hard to turn, and actually turned the motor over.
I had a real good look at the prop and cant see anything obvious as to the prop spinning on the hub.

 

[Wavewarrior]

mark hub and prop , run it , see if marks changed , sounds like spun hub 100%

 

[Holy Shamolee]

mark hub and prop , run it , see if marks changed , sounds like spun hub 100%

I'll try that and get back to you.
thanks

 

[KJM]

Agree, likely spun hub, i had the exact same problem one time, same symptoms.

 

[QBhoy]

Check what prop pitch is on it. Think you are measuring the diameter there. That’s not of so much importance as pitch. Cheers