New to me boat and have a prop question

[PatinIdaho]

Here is the boat so you can see the style.
http://spokane.craigslist.org/boa/4596445408.html

The prop that is on the boat is a 14X17P and I know it is not big enough. It would work good for pulling up skiers I suppose but I will use it for fishing and just cruising. If I pull a tube the current prop will work.
Here is how it acts now.
Gets up on plane easy. Top speed is 31mph(gps) at 4400 rpm at about 1/2 throttle. There is no way I can go WOT once on plane as the engine would blow from over revving. I can go WOT from dead stop until I hit redline then I back out of it.
It has a Volvo penta 280 out drive with a 1.6:1 gr and a aq225D engine 225HP(chevy 305)
Boat weighs about 2000# Also I have tried online prop calc but I guess I don't understand how to use them.

Any one have a idea where to start for a prop search?

 

[steelespike]

A very nice looking rig.
While your 17 may be too small I do suspect your tach is reading in error too high. 4400 at 31 calculates to 29% slip.
Slip at full rpm is usually in the low double digits. ie.:13%.If we go another way use 17" prop 13% slip at 31 mph we get about 3500 rpm.
You need to verify your tach. Borrow a shop tach,get a induction tach.
There is a trim switch on the back of the tach note its position and operate it a few times to clean the contacts.
As far as running over the red line thats no problem for a healthy motor to test. 4400 is for everyday operation occasional wot operation for
reasonable extended time. After you confirm/replace your tach you should be able to do a wot rpm and speed test.

 

[Chris1956]

Gee, a 305CID motor in a 17' Trihull seems like it is overpowered. I agree that your tach is reading incorrectly. Maybe they pulled out the original IL4 and forgot to replace/reset the tachometer? That boat should hit 40+MPH, with the right prop.

 

[steelespike]

NADA lists a 1850 18' with a 170 hp and a 175 17' with a 140. Thats it for 79.
So it appears the 225 is an after market addition. I think the 175 was 1600 lbs with the 140.
Could be under 2000 with the 225.
I think we're talking speeds over 50. Handling may be tricky at speed.

 

[Starcraft5834]

I agree with Chris a 305 in a 17ft trihull with the correct prop should fly..... 4400 at 1/2 throttle? tac is off........verify tac is right.. 19 prop for that rig is about where I'd start.. Ideally, you need to be able to test some props,, maybe local vendor would allow you to do that...

 

[PatinIdaho]

Thanks guys. I'll look at the tach tonight and hook up a shop tach and report back.

 

[PatinIdaho]

Oh also. Don't think there was a engine change. If there was it was a pro job! Everything looks stock with no unused holes any place

 

[steelespike]

Oh also. Don't think there was a engine change. If there was it was a pro job! Everything looks stock with no unused holes any place

It's possible my info just covers entry level setups.