Prop Issues with 1997 225HP Evinrude--WOT RPMS

[Rogue I]

I have a 1997 225 Rude that was rebuilt this past winter (new wisco pistons, etc etc). I followed break-in to a tee, and the engine runs great!

I have a 1978 23' Mako with 19 degress of deadrise. Current prop is 15x17aluminum. Hull should weigh apr. 2500lbs (hull only). With about 50 gallons of fuel, myself (200 lbs) and of course the 480lb Evinrude, I can only push 5300rpms for 32mph or so. So, I moved down to a 15.5x15 aluminum, and can get about 5500-5600rpm and 34mph.

My questions: 1) Dont I want to be hitting more like 5700-5800 at WOT (I rarely run it there btw)? Should I move down in pitch? Is the engine mounted too low?

2) Isnt 34mph for WOT a bit slow? It runs at like 26mph at 4200rpm.

THanks for all your help. If the 15.5x15 is the wrong setup, I need to know soon so I can take it off and return it

 

[walleyehed]

Re: Prop Issues with 1997 225HP Evinrude--WOT RPMS

The numbers with the 15 show about 21% slip...a bit high...
Speed taken with GPS?
Do we know the tach is accurate?

 

[Rogue I]

Re: Prop Issues with 1997 225HP Evinrude--WOT RPMS

Yes, with GPS and with my transducer from the FF. Tach is pretty accurate, I do believe.

I can raise the engine one more hole--should I? Anything else I can do?

Thanks!

 

[walleyehed]

Re: Prop Issues with 1997 225HP Evinrude--WOT RPMS

Are you saying you have one set of holes left to be all the way up on the transom?
If so, where is the Anti-ventilation plate in reference to the boat bottom?

 

[Rogue I]

Re: Prop Issues with 1997 225HP Evinrude--WOT RPMS

They seem about even--let me double check.

 

[Rogue I]

Re: Prop Issues with 1997 225HP Evinrude--WOT RPMS

Okay, I looked again, and the anti-ventilation plate is it seems a few (3-6") below the bottom of the transom. This is a rough estimate because the boat is in the water moored.

Should I raise the motor one more bolt? Should I go down in pitch? Should I ventilate?

I'm really confused 8) What slippage numbers are okay/acceptable for my setup?

Thanks!

 

[walleyehed]

Re: Prop Issues with 1997 225HP Evinrude--WOT RPMS

It's hard to tell if it's in the water...
It kinda sounds like, if you have to lift engine to last hole, and AV plate is still below bottom of boat, we have the wrong shaft-length motor on that boat.

 

[Rogue I]

Re: Prop Issues with 1997 225HP Evinrude--WOT RPMS

I may have misjudged. I have a 25" gearcase, so it cant be the wrong height...

Where should the anti-vent plate be?

Either way, it sounds like it should come up a hole huh?

 

[walleyehed]

Re: Prop Issues with 1997 225HP Evinrude--WOT RPMS

It "should" be even with, if not slightly above the boat bottom.....at the lowest point if it's a stepped hull.

 

[Rogue I]

Re: Prop Issues with 1997 225HP Evinrude--WOT RPMS

It is even with or slightly above the hull bottom right now. I can have the motor trimmed way the hell up though and still have the prop in the water however.

Perhaps moving up a set of holes is worth a shot?

 

[walleyehed]

Re: Prop Issues with 1997 225HP Evinrude--WOT RPMS

It's very unusual to have an engine in the highest position, and yet the AV plate is just now "even" with boat bottom.....strange set-up......
Well, if we can't go any higher, we need to find a prop that runs best at that heigth...