Which prop sounds right.

[thx997303]

I have a 14 ft fiberglass boat, generally loaded with two 20 pound anchors, 2 life jackets, 6 gallons of gas, 2 rather small individuals (one is about 100 pounds the other weighs about 140), a small cooler full of drinks, fishing tackle, and that's pretty much it.

I have a Johnson 9.5 HP outboard on it.

I have two props for it, one a 8.25 x 8.5 IIRC and the other is an 8.25 x 11 again IIRC. Which prop does it seem like would work better?

I understand this will essentially be a WAG, but any help would be appreciated.

 

[thx997303]

Re: Which prop sounds right.

Forgot to add, the 11 pitch seemed to not allow the outboard to rev, but I don't know because I don't have a tach.

Also, they both are aluminum.

I have not used the 8.5 pitch.

The 11 pitch was used with the load described in the above post.

 

[trendsetter240]

Re: Which prop sounds right.

It's hard to say really without a tach. What year is the motor? Is there a specific problem that you are trying to correct?

You could always try out the other prop and see if it performs better.

 

[steelespike]

Re: Which prop sounds right.

The motor came with a 8 1/2" pitch the 11 would be for a very light boat and load.
Use the 8 1/2" If you want to improve your performance 2 light weight danforth style anchors. will help. careful placement of weight and motor trim are important.
3 gallons of gas would last about 3 hours at wot(wide open throttle)A plastic tank
will save weight.If the boat isn't too heavy it should plane easily. A tinytach is about $40 and easy to install, with a gps would tell you if your getting all you can get and in the proper rpm range at wot.

 

[thx997303]

Re: Which prop sounds right.

I will have to go out and compare the two props using my gps.

The outboard is a 67'

When you mentioned Danforth anchors to save weight, I realized that I have two of those. And I was wrong on the 20 lbs. They are 10 and 13 lbs respectively.

The boat is a Fabuglas 14 ft. Everything I can find seems to suggest it is a Trident 146 but I was under the impression the trident was a tri-hull. Of course this is important because I'm trying to get a rough estimate of weight.

Anywho, the trident 146 is a 550 lb boat according to my research.

 

[thx997303]

Re: Which prop sounds right.

I took the boat out yesterday.

With the 8.5 pitch prop installed, similar load to the original load mentioned, and relatively calm conditions, my GPS said I topped out at 7.1 mph.

I'm wondering if this is what i should expect or what?

 

[steelespike]

Re: Which prop sounds right.

It obviously wasn't planing.You could try a 7" As a test perhaps you can empty the boat and see if it will plane.Be sure the motor is trimmed in.
If it will plane we can at least tell if we have a chance of getting it within its rpm range. If you can rig a tiller extension so you can sit farther forward it might help.
Be sre the trhrottle plate opens all the way and it is running on both cylinders.
Idling; just unhook one plug wire at a time. If one cylinder is dead nothing will happen when you unhook it.

 

[thx997303]

Re: Which prop sounds right.

The motor is running perfectly.

I do believe the boat was planing. The front rises and appears to mostly skim over the water.

I of course do not know if the boat is in the right RPM range. I really need a tach.

Maybe I am over-propped?

The two danforth anchors were in the bow, as well as three life jackets, two coats and a blanket. The anchors weigh 22 pounds together and each have 100' of rope on them. 3/8" poly IIRC.

I have a 6 gallon plastic fuel tank located in the back, some tools oil and other things in a small military ammo can. The narrow ones. It was also in the back.

I had a small battery also in the back. I weigh 140 pounds and can only guess that my mother in law who was seated up front weighs 160 - 180 lbs.

That was the entire load when I tested for speed.

I assume my trim should be set as if the boat was on plane?

This link is a pic of how the outboards sits on the boat.

http://i312.photobucket.com/albums/ll331/thx997303/Boat/100_2471.jpg

 

[thx997303]

Re: Which prop sounds right.

Is a 14 foot fiberglass too much for a 9.5 hp outboard?

 

[NoKlu]

Re: Which prop sounds right.

There should be a plate somewhere on the boat that gives you the maximum power the boat should have. That should tell you if you are underpowered.

 

[thx997303]

Re: Which prop sounds right.

I have searched all over for that plate, and it is not there.