minor issues.....?

[Brian66D]

I took my boat out for the first time this year....last year I ran a 3 blade 21p prop and everything was fine. 4400rpm max, decent top speed

(3.0L MerCruisier / alpha one)

I wanted a better prop for wakeboarding so i did some searching on the forums and I went with a 19p 4 blade prop...it is a 14.25 and my 3 blade was a 14.

My max rpm I can get to is 4000. Top speed feels slow also which I know it will be but it doesn't feel remotely close to where it was last year...

should I change pitch? i do like the 4 blade i just wish the boat was a little faster and it doesn't even really seem that peppy out of the hole...about the same as the last prop.

any advice would be appreciated! Thanks!

 

[90stingray]

Re: minor issues.....?

Did you do a ss or alum 4 blade? I am betting you went ss and it has some cupping to the blades. If so, i would think i 17p would be in order since the 21p was almost too much to begin with.

 

[Brian66D]

Re: minor issues.....?

it is aluminum...

today I had myself (just under 200lbs), the ole lady (110lbs maybe?) and another couple who combined are maybe 350lbs in the back....the boat was struggling to get on a plane worse than it ever did with the 3 blade. I also had a full cooler and other misc items in the boat....

I thought the 4 blade was supposed to give me a better shot out of the hole and plane faster?

 

[steelespike]

Re: minor issues.....?

Unfortunately these things happen. Perhaps the prop is marked wrong or in the wrong box.
Did you try the old prop to see if something else may have caused the poor performance?
Is the prop new?If you stick with the same brand usually the results are more predictable.
Any boat might struggle with weight added to the back.
Your 21 was really more for speed and not likely to do well with water sports or heavy loads.
Your selection makes sense your rpm was slightly low and a 4 blade usually suggested to lower 1".
Should have been right on with the 2" reduction.
A 3 blade 19 same brand/model should help with water sports and put you at about 4800 lightly loaded.
Maybe take the 4 blade to a prop shop see if it really is what it says.

 

[Brian66D]

Re: minor issues.....?

Unfortunately these things happen. Perhaps the prop is marked wrong or in the wrong box.
Did you try the old prop to see if something else may have caused the poor performance?
Is the prop new?If you stick with the same brand usually the results are more predictable.
Any boat might struggle with weight added to the back.
Your 21 was really more for speed and not likely to do well with water sports or heavy loads.
Your selection makes sense your rpm was slightly low and a 4 blade usually suggested to lower 1".
Should have been right on with the 2" reduction.
A 3 blade 19 same brand/model should help with water sports and put you at about 4800 lightly loaded.
Maybe take the 4 blade to a prop shop see if it really is what it says.

that could be one explaination for the issues. I do not have the old prop anymore because I threw it away. It got mangled a little bit at the end of last season....I bought the prop brand new right here on iboats and did hours upon hours of research before buying one....I thought I was making all the correct choices. Not sure of the old brand but the new is SOLAS. Bought a new nut, tab, and washer to go with it also.

I did have to buy an offset trim tab for this prop to fit but I know that has nothing to do with what is going on. My boat never struggled before in the same situation with the same amount of weight in the back....I don't know what is going on really.

I could wakeboard behind the boat last year with the 3 blade, and i went to four to make it easier....but i feel as if it is going to be harder with this prop.

 

[Brian66D]

Re: minor issues.....?

any suggestions?

 

[steelespike]

Re: minor issues.....?

Are you sure something hasn't happened to the motor over the winter(first time out)?
Could be as simple as a plug wire off or a bad plug.Throttle not opening all the way?
Do you have a friend with a 19" or 21" prop you could try?
What we're missing here is your old actual original rpm and gps speed.
I wonder if the old prop had high slip numbers or perhaps it was a 19 and not a 21
Slip would allow the motor to rev a little easier but would probably produce lower top speeds.
I hesitate to keep throwing props at it.I do wonder if miss label or miss packaged.
some years ago I bought a vintage Jabsco 6 volt bilge pump Very hard to find any 6 volt pump at the time.
when I got it it was a 24 volt in a 6 volt box.The vendor fully reimbursed me.
Point is maybe a prop shop can check it for you or contact Solas. Have you contacted iboats?
based on your results and assuming the new prop is correctly labeled it would seem that a 17" pitch would get you back to
4400 rpm. If memory serves me It seems I recall some 3.0s using 17" props for water sports.
As thoughts develop as I write this (takes me forever) does seem that the a 19 might be too much.
It also makes me wonder a 21 letting you do water sports without a big struggle.