1977 Topaz Inboard Will only tach 3200 at wot

[usla1]

I have a 1977 Topaz 24ft CC Sportfish (made now by bimini marine) 5000lbs Inboard. It will only tach 3200 and 27 mph at wot. It has a 350 chevy with a 1:25:1 Powerslot (velvet drive) I am running a 16/18 prop which i have checked for accuracy. What's holding me back?

 

[walleyehed]

Re: 1977 Topaz Inboard Will only tach 3200 at wot

Have you verified your tach with a shop tach at WOT?

 

[usla1]

Re: 1977 Topaz Inboard Will only tach 3200 at wot

Have you verified your tach with a shop tach at WOT?

I have verified. And replaced the tach.

 

[walleyehed]

Re: 1977 Topaz Inboard Will only tach 3200 at wot

OK, has it been running this way? is this a new to you boat?

 

[usla1]

Re: 1977 Topaz Inboard Will only tach 3200 at wot

OK, has it been running this way? is this a new to you boat?

New boat to me, The previous owner didn't know that this was odd. The only thing abnormal about the boat is that it has had a large keel attached by a boat builder. It runs fine, smoothly, but just seems to feel as though it is under load.

 

[walleyehed]

Re: 1977 Topaz Inboard Will only tach 3200 at wot

Maybe we need to look at a lower pitch prop..especially if extra Keel was added..depending on how much, it may create enough drag that it's causing problems.

 

[steelespike]

Re: 1977 Topaz Inboard Will only tach 3200 at wot

Have you checked the motor tune and compression.

 

[usla1]

Re: 1977 Topaz Inboard Will only tach 3200 at wot

I am working on the tun, carb n everything else now. The bot ran smoothly, but we'll see. I will let you know what I find.