Prop advice

[j.e.hagen]

I have a 18x44 tunnel hull with 2000 model 40 mariner the prop I'm running is stainless 14 pitch, it seems like my motor is running up to many RPM any advice?

[CajunChristian]

Originally Posted by j.e.hagen

I have a 18x44 tunnel hull with 2000 model 40 mariner the prop I'm running is stainless 14 pitch, it seems like my motor is running up to many RPM any advice?

Have the prop cupped to run on a tunnel. It's called cavitation
D

[ml2oo3]

x2 What type of prop are u running on the tunnel a round ear blade or semi cleaver?

[j.e.hagen]

Round ear, it has some cup in it already you saying I need more Cajun Christian?

[CajunChristian]

Originally Posted by j.e.hagen

Round ear, it has some cup in it already you saying I need more Cajun Christian?

How many rpm's and mph? That will tell you how much slip. You can then reduce slip with cup. Tunnel boat props require a ton more cup than flatbottoms.
D

[cmcnabb]

Hagen bring that prop to Doug. He said he used to cup props for fun on his hitch with a ball peen hammer

[jchief]

What would make a tunnel pull hard to one side? Prop is fairly new and it has been worked on

[Raymond]

Originally Posted by jchief

What would make a tunnel pull hard to one side? Prop is fairly new and it has been worked on

Tab not set properly, too much prop out of the water wide open. Mines pulls a bit at top end even with tab turned all the way to the opposite side but not unmanageble. You'll loose it if the tab ever comes off (don't ask).

Any advantage of running a clever prop on a tunnel hull rig??

[jchief]

Had the tab all the way over and it still pulled. Going to put a torque tamer on it. Just looking for ideas.

Shawn said his fell of and it quit pulling at all.

Thanks.

[j.e.hagen]

I got my prop turned up to 15 pitch, recupped, and repolished it seemed to run great. The only thing I noticed is that it runs much better when whoever is with me is in the back, when someone is in the front it doesn't bite, but I'm happy with that.

[ml2oo3]

Originally Posted by Raymond

Tab not set properly, too much prop out of the water wide open. Mines pulls a bit at top end even with tab turned all the way to the opposite side but not unmanageble. You'll loose it if the tab ever comes off (don't ask).

Any advantage of running a clever prop on a tunnel hull rig??

Semi cleaver props have alot better bite at higher trim settings than a round ear blade all I run on tunnel boats. Four blade semi cleavers work very well on tunnels also.