Proper prop question

[albella]

I'm sure this is the millionth time this question has been asked here, but here goes.

I have an 18' fiberglass Angler center counsel with a 115hp Merc. 4 stroke. Total package weighs about 2200lbs and max out at 5800 - 6000 rpm. The holeshot on it is PAINFULLY slow and top end is ok at 39mph. I'm looking into a Piranha prop. Trying to decide between a 4 blade - recomended 13 x 22 - or a 3 blade 13 x 19

Any advice?

Thank you.

 

[180shabah]

Re: Proper prop question

What prop is on it now? Is it in perfect condition?

 

[bowman316]

Re: Proper prop question

what pitch do you have on there now?
i had a really hard time getting on plane with my original prop, i went down a few inches in pitch and it was like night and day.
just go down 2 or 4 inches in pitch. lean towards 4

 

[albella]

Re: Proper prop question

both boat and motor are a 2007, the prop is perfect. I belive it is a 14x13. Yes, it takes a looooong time to get up on plane. I figure the 4 blade will help a bit and if I goto a longer pitch it will help on the top end also.

 

[bowman316]

Re: Proper prop question

you have a 13 inch pitch on that thing? no way, are you sure about that?
it should be around 21, or even higher.
i have a 70 hp engine, and it jumps out of the hole really quick with a 15. i oculdn't even put a 13 on my engine, much less one with more power.
i would suggest around 17- 21 in pitch.
somewhere in that range.

 

[albella]

Re: Proper prop question

My bad, 13 x 14! Still a very undersized prop. The 4 blade i'm looking at is a 22 and the 3 blade is a 19.

 

[Silvertip]

Re: Proper prop question

I assume the 5800 - 6000 RPM number you indicate is OBSERVED rpm and not just what the manual says. If you think your holeshot is bad now with a 13 x 14P prop just wait until you install a four blade 13 x 22. You will be very disappointed and will have learned a very expensive lesson is why prop selection needs more thought than just slapping a prop on with more pitch. If your engine runs 5800 - 6000 RPM at wide open throttle now, it will be lugging severely with the new prop because a 22P will pull 1600 RPM off the WOT rpm (roughly 200 rpm/inch of pitch). You have the correct prop now. If you want to increase hole shot, you DECREASE pitch not increase it. The effect of that RAISES engine rpm and DECREASES top speed. This is just like the downshifting in your car.

 

[bowman316]

Re: Proper prop question

something is not right with your engine if you have a 14 on there and it is not jumping right on plane, unless your engine is over reving, and that is why it can't get on plane

 

[180shabah]

Re: Proper prop question

Something is not right with your numbers.

5800-6000RPM - 2.0-2.2gear ratio(guessing) - 14" prop - 39mph

All this adds up to ZERO or NEGATIVE prop slip(+/- due to the variables)

FWIW - 17" prop with 2.2 ratio and 6000RPM will give you 39mph with 11% slip.

 

[steelespike]

Re: Proper prop question

Painfully slow is a little subjective.How long to plane?Does it seem that it isn't going to plane.Is it slow with a light load?Is the boat stern heavy?
Is the speed by GPS?Is the tach accurate?A SS prop will usually improve overall performance.Also Hustler props are said to give close to SS performance at aluminum prices.I would start with a 14.

 

[bowman316]

Re: Proper prop question

i guarantee that you don't have a 14 ' pitch on there, maybe a 24. 24 woould sound about right. Go physically check the number again on the prop

 

[albella]

Re: Proper prop question

Well, let me take a step back. This is my first 4 stroke outboard. It just does not have the umf that I am looking for. I'm just guessing, but it seems to take 45 to 60 seconds to get up on plane and from there another minute to reach full speed. I am using my GPS as a guide. Don't get me wrong, The boat/motor combo runs awesome, I'm just looking for a bit more performance on both ends. I know with props you get one and not the other, but, I am looking for an aftermarket prop that will boost overall performance.

I can be wrong about my stock props dimensions (she's in storage for the winter now)

 

[180shabah]

Re: Proper prop question

"seems to take...", "...the unh I'm looking for..." and uncertain prop specs, and an approximate WOT RPM.

I wouldn't buy anything until spring. Get a stop watch, the actual specs for the prop, your GPS and a make sure the tach is accurate. Retest and post the results.

Hustler props were mentioned above - I can attest to the great overall performance. They are vented from the factory. This helps with hole shot, and as far as I know this is the only aluminum prop that comes vented. My current spare propis a 21" hustler, that replaced a 21" blackmax. My hole shot improved(comparable to a cheap 4blade that I tried) and my WOT speed increased 3mph at the same RPM. I still use it whenever we go to new areas or if the water level is low at home. The new Hustlers use the standard Merc replaceable hubs. However, without a solid baseline(we will wait till spring for your testing results) any prop selection at this point would just be a WAG.

 

[albella]

Re: Proper prop question

Yep, that is my plan. I'm just trying to compile as much information over the long Buffalo winter so I will be ready in when the Ice Boom comes out!

 

[Irv964]

Re: Proper prop question

Yep, that is my plan. I'm just trying to compile as much information over the long Buffalo winter so I will be ready in when the Ice Boom comes out!

This link should provide some good information for your long Buffalo winter, it is my review of the Turning Point propeller I put on my boat this summer.
I also agree with the other posters here, something just doesn't sound right with the info you supplied.............Irv964

http://forums.iboats.com/showthread.php?t=269778&highlight=my+review

 

[albella]

Re: Proper prop question

Thanks Irv, Very interesting reading.

 

[Senderofan]

Re: Proper prop question

I think you'll be much happier once you make sure your propped the way you should be. I think there will still be a slight difference in acceleration...if you're comparing the 4S to a two stroke. My father had a 17 foot with a Yamaha f115. Nice combo...but it took a little longer to get out of the hole than my 18 1/2 with a 2s. Just some minor differences...plus, you've got a good sized boat and it would probably benefit from more HP's if you were very concerned about hole shot.

Good Luck,

Wayne