What propeller is this, and what is the best upgrade for me?

[catfighter]

Hello, I just bought this outboard with a propeller that has seen better days. It looks pretty chewed up imo, though I'm new to boats (w/ motors).

Anyway, here is the pertinent information I have, and the information I am looking for:

1) Performance issue you are trying to correct. I feel like my boat could be going faster. it's probably going about 15mph, but I think the chewed up prop is causing the motor to be less efficient.
2) Current prop manufacturer, model, aluminum or stainless and as a minimum. it's aluminum; other than that I don't know. pictures are below
3) Current prop diameter and pitch (required). This is one of the questions I have. What is the pitch and what is a BETTER pitch for my boat (to make the boat go faster)?
4) Wide open throttle RPM and speed with an average load (very helpful) Sorry, I don't know this; the boat will be carrying no more than 600#
5) Engine/drive make, model, year, and HP 1983 Johnson 15hp
6) Boat make model, year, length and weight 1983 Sears gamefisher 14' fiberglass tri-hull, approx 250#


Also, I was looking for a good prop upgrade for under $100.

thanks for the help!

 

[catfighter]

Re: What propeller is this, and what is the best upgrade for me?

Sorry, I looked at the propeller more closely and got the following:

9 1/2 x 10

So the pitch is 10", I presume?


So here's the situation:

My boat seems to have a good hole shot; I would say it planes my boat in less than 20' probably. It also planes very high; I would actually be willing to reduce the amount that it planes to get a little faster, considering it's only going about 15mph anyway.

So I should get a propeller with a higher pitch? I understand it will decrease the RPMs, but that's better than increasing them to an RPM that is too high, right?

Should I go with an 11" pitch with this application, and will it result in faster top speed? Will it be okay to use with my motor?

http://boatpropellers.iboats.com/Johnson/15_HP_(1974-2005)_11.00-Pitch_Black_Diamond_QA3170R_Propeller/761/18881/?**********=074608876&*******=782984548 is the propeller I will probably end up getting, btw.

 

[steelespike]

Re: What propeller is this, and what is the best upgrade for me?

It would be a good idea to get a tinytach(reasonable and easy to install) so you could be sure of your rpm.
A gps for speed would be excellent as well.
Standard prop is a 9 1/2 X 10'.
I would stick with the same size.The motor is capable of 7,000 rpm but I wouldn't reccomend a higher pitch without a tach.
If the bow seems high trim in a notch,More later.

 

[catfighter]

Re: What propeller is this, and what is the best upgrade for me?

If you increase the pitch, you lower the RPMs, right? If you decrease the pitch the RPMs increase.

In other words, you don't run a risk of doing irreparable harm to an engine if you increase the pitch a notch.

I'm new to this, so I don't know. All I know is I feel like the boat is going to go vertical on me at WOT (it isn't, just feels like it), and I could use a higher stop speed.

 

[steelespike]

Re: What propeller is this, and what is the best upgrade for me?

I wouldn't change props without a tach. Its not good to over rev any more than it is too lug a motor.My 5 year old Grandson could install tinytach with my close assistance.
If your hole shot is good your not likely to need less pitch.Move things forward if the bow seems high.Trim in a notch.
How much do you weigh? Be sure the throttle is opening all the way.
is the bottom clean.Your dinged up prop is surely eating up your speed.
Motor under ideal conditions could do about 25(light reasonably fast boat)
I would call your boat average. stock prop should work.A new prop will surely improve your speed.
If the boat is running bow high Sounds like a trim or weight distribuition
problem.A tiller extension may help so you can sit in the middle seat.
Also if the motor is very low on the transom.Antivent(cavitation plate) even with the bottom is considered a starting point.Most endup slightly higher.You can raise by adding 1/4" sticks on top of the transom.Just be sure clamp has a good bite and it pumps water.Raise the motor to a point just before venting(cavitation) becomes a problem.

 

[catfighter]

Re: What propeller is this, and what is the best upgrade for me?

Thanks for all the good advice!

I have a short-shaft motor . . . I believe I may be able to raise it up a little bit.

Should I put the motor at an angle or keep it parallel to the transom? I always put it sticking out a little.

Angled . . .

versus parallel:

Maybe this is causing the slow speed and/or the bow rising up on me?

 

[hwsiii]

Re: What propeller is this, and what is the best upgrade for me?

Fighter, if you will listen to Spike he will get you setup right.


H

 

[catfighter]

Re: What propeller is this, and what is the best upgrade for me?

It's the trim! Look at it . . . it's set all the way to the last hole, which is why it's planing so high!

i guess I need to adjust that down a couple notches. . . i will do that and I will get a 9.5 x 10 prop like Steele suggested. I'm sure I will be fine.

Thanks for the help!

 

[steelespike]

Re: What propeller is this, and what is the best upgrade for me?

When you get the new prop If you get us the max rpm and gps speed with a light load we can help you refine things if needed.Any changes you make do one at a time so you know what the results are for each.
If the boat runs fastest possible it will save you a little time and fuel.
I may even be possible to throttle back and still go faster than you are now.

 

[catfighter]

Re: What propeller is this, and what is the best upgrade for me?

Thanks again for the help; I plan to get a tach soon.

A change in tilt made all the difference. I'm going at least 25mph now (my river is next to a road where the cars are going 45mph). I ran the motor for over an hour and everything is working great.

As soon as I get a new propeller, I'll revisit this.