Help choosing right Propeller

pmjr0987

Seaman
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Jul 11, 2010
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My boat did not come with a Propeller so I got one off Craigslist to start off and am now wondering if I made the right choice

My boat is a 1985 4winns horizon 19.5 cuddy

Mercruiser 260 5.7 v8 with alpha 1 v8 (1.5 ratio I believe) outdrive

The Propeller I got is a quicksilver stainless 19p and 14" diameter

Took the boat out Saturday after doing all maintenance I could think of before going for the first ride as the boat sat for 2 years, maybe more

Top speed according to GPS I got was 47 mph at 4,000 rpm. Give or take 5mph because the current was moving pretty good on the Hudson river and could scew that I think

The boat seems to rev quick coming out of the hull, seems like the Propeller slips when I give it throttle idk if its because its a 14" diameter or if its the 19p I kinda wanted a 21p but 45+ mph at 4,000 rpm seems pretty good

It won't go past 4,000 according to the tachometer you can hear the engine bog as it gets into the 4 barrels but I ran a mix of the old gas with new gas and two bottles of seafoam lol so it could have been a fuel issue their or perhaps the carb needs a rebuild. It did idle fantastic and shift super smooth at idle and rev smooth untill I got close to full throttle it would bog

2,700 rpm netted me about 26-27mph cruising

What do you guys think? Bad pitch, too small diamiter or is it just the way it should be?
 

Sea Rider

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Sep 20, 2008
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What's the max wot rpm for that engine ? The test was made lightly, medium or heavily loaded ? It's near impossible to dial best prop on a blind purchase, yours could be on its way to become spun, make a hub slip test to confirm prop is shot or in good working cond. Can go from there selecting a nice prop to suit best your application, say boating lightly loaded, family oriented, skiing, speeding, etc.

Happy Boating
 

pmjr0987

Seaman
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Jul 11, 2010
Messages
71
Oh ok I'll give you some more info

Full tank of gas (28 gallons) and about 400# of people (two men) were on the boat, water pretty calm maybe 1' chop tops

I do water ski and I do wakeboard and tube. I also will have the boat with more that two on it. I'll be taking it out again Sunday with 4-5 people to relax I won't be towing anything until I get the motor dialed in

I think max rpm should be about 4600 rpm but again it pulls nice to than and will bog around 4,000 when I try and go harder into the 4 barrels. You can hear the note change and get deeper in tone but it didn't gain any rpm at all

The prop I got used but in new condition. I don't know how to test for spun hub but I think it did pull decent speed though I was hoping for 50-55 mph
 

pmjr0987

Seaman
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Jul 11, 2010
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Basically I'll have two types of boating. Lightly loaded while having as fast a cruising speed as possible

And towing a skiier with 3-5 people on board
 

Sea Rider

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In that case should have 2 props, each one for its own current application. OTOH, It's no good for the engine to pull a skier with that much people on board, you could be lugging the engine badly. Driver, spotter if needed and skier is the way to go. Remember, you need fast hole shot for skier to have fun. Probably can dial a single prop for lightly loaded speeding and 2-3 man skiing team. If with 5 will need a different pitch size prop for that specific application.

Happy Boating
 
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pmjr0987

Seaman
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Jul 11, 2010
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I didn't think it would even be possible to lug a 260 hp motor in a 2500# boat! Didn't think about that. My father had that motor in his huge 1986 bayliner 28' so I figured this motor in my boat should be overkill, as it came I found out with a 115hp outboard all the way to my v8.

Is 14" diameter too small?
 

Sea Rider

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Youy can lug anything that's being powered, floats and has weight on with a wrong prop. It's like pretending going up hill with a car in second gear while starting from a dead stop, too much extreme stress on pistons and rods which is very bad. That's what tachs, prop sizes, pitches are for.

To dial best prop for any current application is not a exact science are there are too many variables to take into consideration as hull shape, HP, trim, weight, engine height, water cond. What's the standard diam prop delivered with than engine ? could play with just pitches sizes maximizing prop. Anyway, whatever prop you choose for your current application must be water tested on a wot trial run.

Happy Boating
 

pmjr0987

Seaman
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Jul 11, 2010
Messages
71
Went on the boat again today. 4 people (650#) 25 gallons of fuel and maybe 50# of gear

3,000 rpm was about 30mph

4,000 rpm is about 40mph

2,700 is 25 mph

The boat according to Nada should be 2500# its only 19.5' and has the v8

I feel like it should be moving a bit better than it is

Also from idle to getting on plane the boat seems the rev alot and accelerate slow out of the hole

I'd like to switch to a larger prop

What's the largest diameter you can get on a alpha one?

Maybe also thinking about a 14.5x19 4 blade

What's the opinions on what's next
 

steelespike

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Apr 26, 2002
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At 42 mph (Current modified) speed your numbers seem reasonable. 14" seems to be the smallest diameter in a 19" prop.
I think the 260 would do better with more diameter The biggest listed was 15 3/10 probably over kill.
I would like to see a light load wot rpm and gps speed.You can check your current with your gps.
 

pmjr0987

Seaman
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Jul 11, 2010
Messages
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That speed I posted was light load but it was probably closer to about 45mph since I was going with the current on the river

I feel like a boat this size should do better than 30mph at 3,000 rpm... Less than 2,700 and it starts to loose plane pretty fast which means the Propeller is slipping alot at lower speeds as the water gets more liquid


I almost want to pull the trigger on a 4 blade 19" like the hustler but don't know if I should do 14x19p or 14.5x17p

These propellers seem to have very good reviews and I think my boat could use a 4 blade to help it get out of the water fast while having good cruising and top speeds
 

steelespike

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Is the 4000 rpm wot Should be about 4800 wot lightly loaded.
I see you have listed a Counter rotation prop I'm pretty sure yours isn't counter rotation . Normal rotation is clockwise standing behind the boat.
Your slip at 3000/30 mph is 16% slip at 4000/40 mph is 16% Certainly reasonable for reduced rpm.
I think the 14"diameter prop may contribute to slip numbers may also account for falling off plane too easily.
A 4 blade should have good hole shot and stay on plane better at reduced throttle.If you go to a 4 blade Hustler I would suggest dropping 2" pitch.
The 4 blade will have about 30% more blade area so diameter may be reduced.
 

pmjr0987

Seaman
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Jul 11, 2010
Messages
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Ok thanks for the replys, I don't believe my engine is running up to perfect yet it doesn't seem to be a power thing but a restriction in either the fueling, spark or intake/exhaust. I'm working on that seporatly though now as well

So the 4,000 max is also 4,000 at 4/5th throttle, the rest of the throttle you can hear the 4 barrels open up but doesn't raise rpm past 4,000 on the gauge

Sounds weird but I watched a video on YouTube of my same boat and looking at his gauges as he cruised he was doing about 2,800 rpm and doing about 32 mpg and the engine sounded more relaxed than mine. Below 26-27mph I start loosing plane a bit as the prop feels like it starts to slip more

Your right idk why I linkrd that one but that's the Propeller model I'm looking at getting in 14x19p

Would really help if I could find out what Propeller my boat came with from the factory but I can't seem to find any info
 

JASinIL2006

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Feb 10, 2012
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I've got a similar setup on a similar sized boat (350 Mag with Alpha One Gen 2 1.47 ratio) and it really seems like you should be getting more out of your boat. I have a 4 blade 14"x18P stainless steel prop (Solas HR Titan), and it has great hole shot (even when pulling a skier with 5-6 people on board) and a top end above 50MPH (GPS measured) at about 4400-4500 RPM. With a 3-blade aluminum prop (don't recall the pitch off the top of my head) on flat water, I can hit near 60 MPH. It sure sounds like you aren't getting everything out of your 5.7 that you should be.

I would think a boat that size with a 5.7 should jump. It might make sense to get the engine stuff cleared up first.
 
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