Prop help?!

B-Buck

Cadet
Joined
Jun 26, 2017
Messages
6
Hi everyone I have a G3 eagle 176 with a 25 hp Yamaha with a 9 7/8 X11 1/4 prop on it and and am only running around 4100 rpm at wot with 2 people and pretty minimal fishing gear. It's a pretty heavy boat at 1100 dry weight. I know it's not going to be a speed machine but I would love for it to plane out! (And I know I'm kicking the hornets nest)...but would a hydro foil maybe help with the planing also? Any help will be much appreciated! Thanks in advance.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Welcome to Iboats,

Don't throw money into the deep blue going for an hydrofoil, there are better ways to make that combo to plane out in terms of OB/transom height optimization, correct trim, prop maximization.

For that will need firstly to buy an inducion tach with adjustable fring capabilities say Hardline, Tiny Tachs to check max wot rpm achieved with 2 on flat calm no wid water cond with current factory delivered prop, from there can go for lesss pitch props to pull wot revs higher towards 5000-5500 wot rpm range.

Happy Boating
 

B-Buck

Cadet
Joined
Jun 26, 2017
Messages
6
I did put an induction tach on and the the reading I was getting yesterday was 4100-4160 wot (water had a little chop to it) as far as hight of the motor my cavitation plate is within an inch from the bottom. And have a manual trim and have it set 1 notch from bottom. I am willing to move or try any suggestions to get the best results
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Try the following to the letter :

Distribute deck weight evenly or sit a boating mate up front to balance combo.

1 Balance & Trim.JPG
Manually trim OB to sit at 90?, that's perpendicular to water level.

Go for a wot spin on flat calm water, once on plane,
Pull head out transom to check what's going on at rear transom.

2 Water Flow Check.JPG

Check at which lower leg is water flow passing at speed ?

90° Angle & Thrust.JPG

Check if Above or Under small upper water deflector plate. If above (1) will achieve water splashes
Out/Over transom, if close to AV plate (2), will achieve excessive prop aeration issues, as in upper pic
to fully understand how prop grips on water.

5 Ideal Water Flow.JPG

This is the Tip-Top OB/transom height for Yams and any other newer brand OB's

Post results...

Happy Boating
 

Maclin

Admiral
Joined
May 27, 2007
Messages
6,761
A smaller boat that is close to being underpowered like that can benefit from Nauticus Smart tabs. Plane at slower speeds, attack angle of the prop can be used for thrust for more efficiency (not having to "lift" anything), examples of things like that are on the Nauticus site. Just a thought.
 

B-Buck

Cadet
Joined
Jun 26, 2017
Messages
6
This trim tabs like that kinda worry me because of the holes that gotta go in the lower part of transom. Once one your stuck with them even if they didn't work very well. But still something to think about
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Will not need those if OB sits at the Tip-Top transom height along a prop maximization for OB to rev to max wot rpm range. It's a day/night difference.

Happy Boating
 

B-Buck

Cadet
Joined
Jun 26, 2017
Messages
6
That's good to know. I went ahead and raised the motor cuz I think it might been a little low an I woulda took the ol girl out today but it's been windy as all crap today.
 
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