serious prop problem-t think

[steam_mill]

History:
I had a 12 foot short shaft aluminum boat. Had a 2004 2 stroke 9.9 merc on it. Transom measured 15 inches. Motor measured 20 inches from cavitation plate to just below the cowl. So, this should be a long shaft motor? Can you confirm?

So, my problem is, I bought a 12 foot smokercraft alaskan. 20 inch transom.

Put my 9.9 on it. Well, my prop slips a lot, can't make turns.

Basically, boat is unusable. Moved weight around in boat. Helped a little, not much.

I'm not able to make turns, prop slips and I come off plane.

Motor is running fine. Only happens on this boat.

Cavitation plate is 2 inches above bottom of boat.

So, is my shaft length wrong?

If not, can I fix this with a prop???

I'm very disapointed...

HELP!

 

[skibrain]

Re: serious prop problem-t think

What is the measured distance from the underside of the mounting clamps on the outboard motor to the cavitation plate? Weblink has some info.

http://www.sschapterpsa.com/ramblings/OB_shaft_length.htm

 

[steam_mill]

Re: serious prop problem-t think

I'm on a blackberry. No internet access at the camp.

It is 20 " from the cavitation plate (plate just above prop) to the area 1"below the joint of cowl to the part below the cowl.

Essentially, same level as lower edge of choke pull.

Does that help?

 

[steam_mill]

Re: serious prop problem-t think

Based on the website, my shaft length is 20"!

 

[skibrain]

Re: serious prop problem-t think

If your choke pull is the same height as your transom brackets I guess that is helpful.

Have you tried adjusting the trim pin? The horizontal pin that can be adjusted to limit how low the motor will be tipped down in it's lowest position.

Is the prop damaged severely?

 

[steam_mill]

Re: serious prop problem-t think

Motor is in lowest trim position.

Prop has absolutely no damage.

From what I've been readin, my prop is ventilating excessively.

So, if I compare the prop on this motor to the prop on my 90 hp merc, the prop (obviously smaller) has thinner blades.

I'm thinking I need a different prop, not just a pitch adjustment????

 

[Mi duckdown]

Re: serious prop problem-t think

NO. from the bottom of the clamp that rests on the transom to the cavitation plate

 

[skibrain]

Re: serious prop problem-t think

From your original post:

Cavitation plate is 2 inches above bottom of boat.

If this is true, you have a short shaft motor with a 17" transom or a long shaft motor with a 22" transom.

 

[steelespike]

Re: serious prop problem-t think

Measure from the clamp where it rests on the transom to the antivent plate just above the prop.probably about 15- 17".if a short shaft.
A 4 blade prop might solve some of your problem.