prop questions 9.9 hp

[Drewdaddy]

I have a evinrude 9.9 hp 1987 and it is on a small fiberglass boat. The boat is rated for 10p max but I am having a problem with the motor performing well with two people and gear in it. The front end tends to plow and I can tell the motor is not as wound out as it is when I am by myself. How would I go about figuring out the proper prop that I would need when running all this extra weight? Any idea what the stock pitch and diameter is? If I get a new prop to make the rpms higher when loaded down and run it with just myself in there at other time, can I risk damaging the motor?

 

[Mas]

Re: prop questions 9.9 hp

Is the cav plate even with the bottom of the hull? Many times a long shaft motor is placed on a shallow transom thus creating planing issues.

Try moving weight to the stern until she gets up on her feet.

Also, how is the motor trimmed?

MAS

 

[Drewdaddy]

Re: prop questions 9.9 hp

It is a short shaft on the proper boat. The transom was 15" or 16" last I checked. The motor was set on the lowest setting to try to get the boat on plane faster, I assume that is what you mean by how was the motor trimmed. I did play with the different height adjustments on the motor. We also tried moving trolling motor battery front to back and tried switching places (he is about 85 more pounds than myself). When I was up front being lighter it did perform better but still did not seem to get to the point it was ready to plane (although it did seem closer to that point).

 

[alangf]

Re: prop questions 9.9 hp

The cavitation plate (that's what it's called but not really what it is) on the engine should be roughly parrallel to the boat's keel. If you have the trim set all the way down it will force the boat's stern up and the bow down. For what it's worth, cavitation occurs when the action of the propellor causes enough pressure reduction in the area of water forward of the prop the cause a low pressure boil that can pit and damage the prop. The plate above the prop is designed to prevent the prop from sucking air from above. This condition is known as ventilation. The plate almost universally called a cavitation plate is actually an anti-ventilation plate.

 

[Mas]

Re: prop questions 9.9 hp

Any chance your boat is foam filled and water logged?

How big is your "small boat?" If the boat is too small with a lot of weight, it will never get on a plane.

MAS

 

[Whoopbass]

Re: prop questions 9.9 hp

Try this link to find the right prop.
http://dansdiscountprops.com/BuyNow/propWizard.cfm
Figure out the pitch you need and then check out the props iboats carry since they have good prices.
A lower pitch prop will probably help.
Your prop should have the pitch stamped in it.

 

[tashasdaddy]

Re: prop questions 9.9 hp

your motor has has a tilt pin, 4 positions, on the transom mount. move the tilt pin away from the transom, when you have another person in the bow, this will pick up the bow.

the further away from the transom the higher the bow.

 

[Drewdaddy]

Re: prop questions 9.9 hp

your motor has has a tilt pin, 4 positions, on the transom mount. move the tilt pin away from the transom, when you have another person in the bow, this will pick up the bow.

the further away from the transom the higher the bow.

This is what I called the height adjustment pin. I did play with this pin and while it does keep the front of the boat from digging, the boat still seems to want to plan but there just isn't enough speed or power.

My boat is a 15'4" Gheenoe that literally weighs 125 pounds minus gear, people, and motor.. It is very small if you are familiar with these boats...

 

[mchin]

Re: prop questions 9.9 hp

drewdaddy, I have a 13 foot gheenoe and have spent tons of time in the 15'4s. because of the narrow transom and canoe shape, these boats love a hydrofoil, also they are can be sensitive to weight adjustments as the wide center of the boat and the narrow stern and bow, it can act like a seesaw. a 9.9 should get you up and running in the 17-18 mph range, depending of course on your load and all. with 2 people, probably in the 15-16 mph range. check out the http://www.customgheenoe.com/ site, create a profile and read the forums, you'll find tons of information. Your boat has a weight capacity of 675 lbs, so unless you guys are bringing along a few hundred pounds of bait, i dunno what else to check. and your boat runs great with one person? if not, then I might suggest checking your motor to make sure it's running right and that the prop is not slipping on the hub. I assume you are running the stock prop, i think it's a 9x9 or a 9x10?

 

[Landscaping Wiz 808]

Re: prop questions 9.9 hp

The original prop that came with my '86 Johnson 9.9 was 9 1/2 X 10 if that helps.

BOB