Sorry, But Yet Another Pitch Question...

[Landscaping Wiz 808]

Hello all,

Before I begin let me state that I tried to look for the answer to my question using the 'search' function, but I wasn't able to narrow down anything close enough to my situation. So with that out of the way...

On Thursday I bought a new Carolina Skiff J14 kit boat with a front deck and two bench seats to keep at my house in Westport, MA. It will be replacing a leaky 25 year old aluminum boat that has been on life support for the past five years.

I've used a 1986 Johnson 9.9hp on the aluminum boat over the past couple years without any issues due to the maintenance schedule I put it on that I learned here. My problem is that the new boat is substantially heavier than the old one and I don't currently have the means to get the 25hp I desire, so for the time being I'm going to have to make the 9.9 work.

The 9.9hp has a 9.5 X 10" prop on it and I know I'm going to need to change it in order to get the new boat on a plane. The Carolina Skiff will weighs between 500lbs-600lbs fully loaded. Can any of you fine members tell me what pitch prop would be best to get her moving at full RPM (5k-6k)?

I tried to provide as much information as I could, please let me know if you need more. I leave for MA on 7/23 and still need to order the prop so the faster I can do so the better.

Here are some pictures of the new boat if they help:

As always, thanks in advance!

Bob

 

[steelespike]

Re: Sorry, But Yet Another Pitch Question...

If we are going to guess a prop we need you to figure carefully your weight list items for us to be sure all are included.You would be saurprised how far off some have been. Also an estimate of the old weight and performance description.hole shot etc.
Best way to go is to get yourself a Tinytach $47 and test run with the present prop
Borrow a gps or clock it with a fellow boater Get us the rpm and speed.
As near as I can tell the bare boat is 300lbs it appears you have added seats and
front platform. then you'll have the motor 80lbs,whatever it takes to secure the seats, tank and gas,anchor,gear,yourself.

 

[Landscaping Wiz 808]

Re: Sorry, But Yet Another Pitch Question...

Thanks for the response! The bare boat is 280lbs, each seat is about 20lbs, and the platform is about 40lbs which equals roughly 360lbs. I weigh 225lbs (+/- a few pounds), 90lbs for the motor & gas tank, and let's say 75lbs for additional gear (anchor, cooler, ropes, etc.) = 390lbs. Grand total as far as known weight is about 750lbs. Just to be on the safe side lets add another 100lbs for a total weight of 850 pounds.

Unfortunately the 9.9hp Johnson is currently in MA and the new boat and myself are in VA so I don't have any way to hook up a tachometer right now. What I can say is that the 12' aluminum boat in MA weighs approximately 150lbs and with the same amount of weight in it (390lbs), the total weight is 540lbs. It has a good hole shot and gets on a plane at around 3/4 throttle. With another person in the boat it takes full throttle to get on a plane. I have a video of the hole shot if it helps.

The current prop has a 10" pitch, I was thinking a good estimated pitch to get the new boat on a plane would be 8". What do you think?

Bob

 

[Landscaping Wiz 808]

Re: Sorry, But Yet Another Pitch Question...

Here's the video of the 9.9hp on the aluminum boat:



Bob

 

[steelespike]

Re: Sorry, But Yet Another Pitch Question...

Well to look at it optimisticaly. Being a 14 footer probably with a little more beam
it may do better with a load with some luck it may do about as well as the other
when a person was added. Check out the tiny tach It could be run temporarily
and should be a quick hook up.Then a test run would tell better what pitch to go to. And if it gets you to the rpm you need.If you must have a prop without a test
I would go with an 8" it may be a little light but you can throttle back a little.
You might consider a 4 blade to help you get over the hump better.

 

[steelespike]

Re: Sorry, But Yet Another Pitch Question...

Boy that really gets up and goes; maybe try it first with the 10" and change based on the results.No doubt will need a change but better to work with rpm.
We know the motor is strong so don't have to deal with motor health.

 

[pduquette]

Re: Sorry, But Yet Another Pitch Question...

Hi Bob ! What is the max Hp of the Skiff ? giving it less than 2/3 required Hp may be dissapointing.....peter

 

[steelespike]

Re: Sorry, But Yet Another Pitch Question...

He mentioned in his first post he'll have to wait for a bigger motor.
I think it is rated for a 30.
By the way Bob check out the Evinrude Etec 25 or 30.

 

[Landscaping Wiz 808]

Re: Sorry, But Yet Another Pitch Question...

If you must have a prop without a test
I would go with an 8" it may be a little light but you can throttle back a little.
You might consider a 4 blade to help you get over the hump better.

Yep, unfortunately I'm going to have to 'blind order' the prop. I was thinking the same thing in regard to the 8", but after looking through the iboats propellers they do have a four blade 9", could that be an option?

Hi Bob ! What is the max Hp of the Skiff ? giving it less than 2/3 required Hp may be dissapointing.....peter

Hi Peter - Great to hear from you! The boat is rated at 30hp. Next year I plan to put an older 25hp-30hp on it, but after buying the boat & trailer I just don't have the $$$ needed to do it this year. So I'm going to have to make do with the 9.9 for now. I know it won't be a speed demon, but I'm hoping to get the best performance I can from it.

Thanks for the help guys!

Bob

 

[Landscaping Wiz 808]

Re: Sorry, But Yet Another Pitch Question...

.
By the way Bob check out the Evinrude Etec 25 or 30.

I've love the Etecs, but since this boat is only going to be used for a few weeks out of the year I think I'm going to look for a '90s model OMC 25-30hp over the winter when the demand/prices go down. I love the old Johnnyrudes!

I'm going to buy the prop for the 9.9hp tomorrow so it can be delivered before I leave. I was considering a 4 blade 9" for a while, but am still worried that I wouldn't be able to get full RPM out of the motor.I think I've narrowed it down to a four blade 8" pitch prop. Any last words of advise?

Thanks again guys!

Bob

 

[Kainon]

Re: Sorry, But Yet Another Pitch Question...

I think a 4 blade 9p would requate to a 10P 3 Blade, though it will give more bite and may help get out of the hole..

If you have a smart phone that has GPS, you might be able to find an APP for it.

 

[Landscaping Wiz 808]

Re: Sorry, But Yet Another Pitch Question...

Okay, the prop I ordered came today, it's a Solas 4 blade - 9.25" diameter by 8" pitch. I sure hope it works better than the stock prop. I also ordered a tiny tach, but don't know if it's going to get here before Saturday when I leave. If it comes later the girl watching my house & cat while I'm gone offered to mail it to me in MA.

I'll take GPS speed and tachometer readings to compare the two and maybe a couple of videos too. I'll post the results when I get back in August. Wish me luck guys! Here's the prop:

Thanks for all the help - Bob

 

[steelespike]

Re: Sorry, But Yet Another Pitch Question...

Good luck we'll be watching for a report.When in doubt its best to go on the light side with a prop change.If it ends up over reving you can still use it and watch the rpm. if over propped you could use it briefly but would need a change.