Speed/RPM/Prop issues?

[mikewojno]

I have a newly purchased 1996 Gibson Houseboat Sport model with 2 305XL Crusaders.
A few people have told me this boat was designed to run up to 4000RPMs and go 20MP.
Engines will only get to about 3300RPMs and boat speed is a little over 13MPH.
Bottom is clean & freshly painted. The engines seem to be running properly.
I think the problem is what they refer to "over popped".
Anyone have experience with this model or an opinion on what is causing this issue?
Thanks
Mike

 

[makomark]

Just my two cents...based of a bit of time spent on the water.....

The engine (not the boat) is designed to achieve a WOT rpm range, based on the gear and the prop, to achieve reasonable performance balanced with longevity.

Could be over propped - check with the previous owner to see if he changed the wheels. You can also check the web to see if you can find out what Gibson provided for the baseline prop size - Gibson houseboat forums, maybe???? you then need to figure out what is currently under the hull. Once that's understood, you need to assess the health of the existing engines...if they are tired (high hour or poorly maintained) there's no way they spin the 'correct propeller' .... anything from frozen timing advance to worn out valve seats will hurt here.

Finally, even if the hull was fresh from the factory with the 'correct wheels', if you overload it, the engines will never hit the WOT rpm band....you can stash a sizable mass on a fishing boat so I'm positive you can pack even more into a houseboat.....many travel lifts have a 'scale function' available...just ask the operator next time you use one.