motor height ?

Benny1963 · Oct 26, 2008

i have a 14 1/4 x21 on my evin 150
it porps before i can trim up to get the extra rpm
will raising motor help gain rpm or help with porping
its currently level with bottom of keel .
but i cant trim up because of porping i need anopther 800 rpm

mthieme · Oct 26, 2008

Re: motor height ?

The cavitation plate should be even with the bottom of the boat. I assume this is what you mean (?).
If you're porpoising, you're trimmed a little too much.

Benny1963 · Oct 26, 2008

Re: motor height ?

yes you would assume so but im not blowing out and its not leting me trim up to get the rpm i need

mthieme · Oct 26, 2008

Re: motor height ?

What kinda boat are we talking about?
Does it have tabs?

Benny1963 · Oct 27, 2008

Re: motor height ?

no its a whaler style boat without tabs it has a 175 evinrude on it its 17ft long a little overpoweredmay have to add smart tabs ,

Dhadley · Oct 27, 2008

Re: motor height ?

Tabs are going to help but you're up aginst a hull design issue. Those style boats will have some handling issues with that much power. A different style prop may help too. If the prop you have now has bow lift you may want to try a prop with stern lift.

There is no set "right" X dimension. It will change with load, use and props. Even is probably a bit low, you might try moving the motor up and see how the hull reacts.

Benny1963 · Oct 27, 2008

Re: motor height ?

mr hadley what stlye should i try im going to pick up motor ,one hole
what exactly is a stern raiseing prop cupped or uncupped ,if i could lift the stern i could trim up give me a suggestion on stern lifting prop or brand or deminsions please woul like to setup without tabs to get wot
my concern is that im under wot and cant trim up withput the porp probs it has plenty of trim left and when run in tank on trailer i can pull 5800
by trimming but bow is strapped down acts different in water im lost
i could just drop pitch and reduce lugging but that doesnt really solve prob
i should be able to turn the 21 thanks dhadley

Dhadley · Oct 27, 2008

Re: motor height ?

It's not so much about cupping or not but rather where the cup is on the blade. Most 4 blade props have more stern lift than bow lift.

Benny1963 · Oct 28, 2008

Re: motor height ?

so i need to try a fourblade should i keep my pitch the same 21p
what prop would you try three or four blade ,or should i put the smart tabs on it then pitch to get wot loaded with them on it
the smart tabs say little or no porping probs is that so ?
by the way thanks man hope you are all good

Dhadley · Oct 29, 2008

Re: motor height ?

I would stay with a 20 or 21 4 blade. If it were me I'd make one change at a time. Either the different prop & test, then tabs or tabs & test the existing prop then a different prop.

steelespike · Oct 29, 2008

Re: motor height ?

Dhadley said:
I would stay with a 20 or 21 4 blade. If it were me I'd make one change at a time. Either the different prop & test, then tabs or tabs & test the existing prop then a different prop.

Like he said stick with one change at a time.

motor height ?

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