what pitch for this orphan deck boat?

[Ark-86]

Hi guys

Sorry to break half the rules with my first question in this forum, but here goes:

A friend and I brought home a newer motor for his recently acquired 26' Peterborough deck boat. The old motor calved right away..( but it worked long enough to show how nicely it would plane and handle)..a 175 Merc with a 5 blade SS prop. This "new" 2002 Evinrude 225 HP came from a small local dealer, with no prop.

We cannot find any info on the Peterborough. It has a solid aluminum modified V or shallow V hull, an aluminum frame, rails, and roof. We plan to have family outings, with maybe 8 or 10 people fishing etc. Would also be nice to haul a skier or 2 from time to time. He has been told by different shops to put everything from a 15 pitch to a 21 on it. 3 blades, 4, 5?

Any clues?

Thanks

 

[Maclin]

Re: what pitch for this orphan deck boat?

Do you guys have any numbers from the previous engine's performance before it cacked? Like WOT RPM or MPH, or really RPM at any known MPH?

Also, call the dealer and ask what that engine drive ratio is, the more real numbers you can get the better the advice will be.

 

[Ark-86]

Re: what pitch for this orphan deck boat?

No numbers. as tach and speedo did not work. Boat has gone in for some re wiring and interior work. Will have it back soon, propless.

Will call dealer for drive ratio, thanks.

 

[steelespike]

Re: what pitch for this orphan deck boat?

If 8 to 10 people is normal I think a 17" is a starting point. Keeping in mind that lightly loaded it will likely over rev.
Maybe you can find a dealer that will let you try props.At the cost even in aluminum I wouldn't want to be buying too many props.
According to my info the 225 is rated at 5500 to 6000. 1.85 ratio
Your better off being temporarily under propped because if over propped you shouldn't run the boat for any extended time
and will have sluggish performance.
If under propped you can control the max rpm and it will have peppy performance.

 

[Philster]

Re: what pitch for this orphan deck boat?

Yeah, if a boat can go from 0-10 people, then you have some choices:

1) make use of two props and change them as your load changes
2) make use of one prop that underprops the boat when lightly loaded, which requires you to act as a responsible helmsman and limit your RPM in these lightly loaded conditions, because underprop-ing means you can blow past the upper RPM limit.

Tachs are cheap. Engines and props ain't.

Get a tach.