Boston Whaler 11' Planing Issue with 15 Four Stroke

[kgs365]

I just refurbished an 11' Whaler. I removed the 9.9 Yamaha 2 cycle and replaced it with a Merc 15 four stroke. The Boat barely gets up on a plane. Any thoughts? Possible solutions might be:

1) Mount motor higher on transome
2) Install hydrafoils on motor (ugly)
3) Prop check (it has a 9 inch diameter prop)
4) Permatrims??
5) By a two stroke 25HP

Any suggestions?
Does anyone have a web site for "proping" this boat.

Thanks!

[baypro21]

Did it plane with the 9.9? What diameter and pitch does the 9.9 have? Try a prop with less pitch. I've got a 15hp 2 stroke Johnson that was on a 14' metal john boat at one time. I don't believe it really planed out fully, it always pushed a lot of water. More hp is always going to be better.

[kgs365]

I sold the 9.9 and did not look at the pitch. Also, the 9.9 was about the same with the planing. THe 9.9 was a 2 cycle while the 15 is a 4 cycle.

Thanks, Sean

[stevec717]

That's a fairly stout little 11 footer. Probably 500 lbs. plus motor you and fuel. That could be 800-900 lbs you're trying to plane with 15 hp. (not easy) Is that max hp for that boat?

[jyasaki]

stevec717 - 5/1/2005 10:17 PM
Is that max hp for that boat?

According to the Whaler website, 15 is max.

I'd try moving more weight up front, followed by a hydrofoil of some sort (the permatrims are another hydrofoil design.)

I don't know that you're going to be able to figure out anything about prop selection before you get it planing at least somewhat reliably.

jky

[mtcfish]

Put sand bags in the bow...

[samblate]

My old boat (soon for sale) is a 14' Fish n'Ski Barge similar to the Whaler -- weighs 550 lbs. plus gear -- pushed by a 15 hp. 2-stroke Evinrude with standard prop -- it never planed either. It would go faster, though, with weight moved forward. Max speed was about 12 - 14 knots with one passenger.

[Afishinado]

Go back to a Merc 2 stroke! It can plane anything....

[tackless]

I've got an 11' whaler with a 15 Tohatsu. I put a dorsal on and raised her up 3 notches from full down on the tilt adjustment. Planes perfect.

[kgs365]

Do you think it is a four stroke issue?

[permatrim]

I don't think it is your motor, unless it is not reaching full throttle.
Your prop size will probably be 9x9 or 9x101/2", they are usually the standard sizes for a 15hp, even your 9.9 probably had a 9x9.

If your motor is revving out properly, and not to deep in the water, then you should fit a hydrofoil, i know you think they are ugly, but they will help a lot.
I have a 12' ali dinghy with a 15hp evinrude and foil, will do 20-25mph with 2 people, and it will plane with 3 adults in it, i can tow ski biscuits with it and my son at 13 could wake board behind it, can't now at 14.
If you go for the plastic foils don't go for ones that are wide, get narrow and long, if they are too wide, they will dig in on sharp turns and could make the boat heel over to far.

Cheers
Colin
Permatrim

[horseradish]

That little boat is a pig! Maybe "Smart Tabs" would pick up the fat, heavy butt enough to plane with a heavy 15 hp four stroke. A Doel type fin might work as long as you limited the load to one person. Face it...that boat's a dingy and you can't expect anything else out of it!

[kgs365]

I found a $47 tach for these small outboards. Will check the rpm and put the correct pitch. I will also install the hydrofoils and let you know. Thank you very much for all the input. I will keep checking in for any additional thoughts.

[ScrubJ]

Where did you find the tach?

[kgs365]

It is a Yamaha Product from Monahans Marine in Weymouth MA. Mounts in front of motor and easy to install. You can buy mine once I check out me motor.

[cduced]

Never used one but there are lots of references to Tiny Tach for an inexpensive tach for small boat motors.* -- Bud

[blacklabmarine]

I recently had an 11' Whaler with a 6 hp Yamaha 2-stroke and I could get my 200lbs on plane - it was all getting my weight forward. I used a long tiller extension and got my body amidships - hope that thi shelps...

[sundancekid]

I just put a 20 Merc 2-stroke on my buddy's 11' Whaler. It'll flat boogie with two people in it, but one person, and it can't get over the hump. Weight forward is the key to an 11'! That 15 should have no problem getting her up with the proper weight and balance. Also, if there are any cracks or old drill holes in the boat, the foam will become saturated and add a lot of unnecessary weight to the hull. The pitch of the prop is a 13, not sure of the diameter, but I wouldn't think it would be much more than 11 or 12".

[bigblue]

kgs 365

fit a Permatrim with confidence -they are THE best foil available, had them on around 5 of

my boats over the years and they fixed porpoising and "out of the hole"planing problems,

they are one of the easyto fit problem solvers in the boating world,

THEY WORK