1998 9.9 power loss

[Harris_166]

I have recently bought a 1998 9.9 mariner. It starts up fine and idles perfectly but when I set out and try to apply full power it seems to not get to max rpms and struggles to move my boat. It is a long shaft on a short shaft boat wondering if that would do anything? Compression is good as well as the spark have tried almost every thing i can think of and nothing has worked.
If you have any suggestion please don't hesitate to reply

 

[MH Hawker]

I t would be a lot of help if you know the WOT rpms

 

[Guest]

What kind of boat you trying to push?

 

[Harris_166]

A 14 foot aluminum

 

[jerryjerry05]

A 9hp on a 14ft anything isn't gonna go anywhere fast!
The cavitation plate is in too deep.
It should be close to the bottom.
1 in either way. Raise it up.
What hole is the lock down in?
Too far down will only make it struggle to lift the front of the boat.
Too far up and it won't be at the right angle.
What was the motor on before?
The pitch of the prop?
They sell an item called a "Tiny Tach" it's an add on for small outboards that will help in diagnosing the proper pitch of the prop.

 

[Harris_166]

We will make a jack plate to adjust the hight. thanks for the info Tiny Tach is there an online link to buy one

 

[Teamster]

My 9.9 Merc kicker ran badly until I ran some Amsoil Quickshot through it and now it's awesome,...

I'm guessing it had a clogged jet,..........

 

[Harris_166]

Put a 5" plate to rase up moter magenal improvement checked spark plugs one was faulty running great thanks for the info everyone