Requesting Prop help

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gbalaz

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Jul 23, 2013
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I just bought a 2001 Crownline 180BR with the 4.3L engine. It currently has an aluminum 14dia and 23p prop on it. I am able to get to about 44mph @ 4k rpm's. I had a 95 Rinker captiva 190 with a 4.3L in it and was able to get to 52mph at 4800 rpm's. I'm not sure what the specs were on that prop and I sold that boat. I know my Crownline can do better, but I am in need of the prop experts to help recommend the proper propeller for my new boat.
 
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Chris1956

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You seem a bit overpropped. Normally, changing to a 21P prop will give you +400 RPM. Changing to a 19P prop will give +800RPM. You may get additional speed, as the motor gets further into it's power band. I do not think you will hit 52MPH, however. I would probably go with the 21P prop.
 
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gbalaz

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Chris1956 said:
You seem a bit overpropped. Normally, changing to a 21P prop will give you +400 RPM. Changing to a 19P prop will give +800RPM. You may get additional speed, as the motor gets further into it's power band. I do not think you will hit 52MPH, however. I would probably go with the 21P prop.
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Something just feels "off". The boat had a 15.5 17p prop on it when I bought it and it was even worse, probably topping out at 3800RPM and less than 40mph so I put the other prop on that the seller gave me which is the 14.0 23p and it didn't seem much better. I hate to "buy" another prop only to guess it will provide me what i'm looking for. I'd like to be able to reach the recommended RPMs at wot, that is 4800 correct? Should I buy a 14.0 19p? I'm afraid to do that knowing the 15.5 17p I had performed poorly. Does that larger dia make that much of a difference? Lots of variables here and I don't want to just start buying props.
 
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Starcraft5834

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"The boat had a 15.5 17p prop on it when I bought it and it was even worse, probably topping out at 3800RPM"


gb... that engine, "if healthy" should be turning a prop at 4400-4800 rpms in it's "sweet spot". what's that? that's the recommended WOT power band with the correct prop for most Mercruiser engines recommended rpm range is 4400-4800. The size/weight/hull configuration/motor power are all different, the right prop for a 3.0 engine may not be the same as a 4.3 or a 5.0.. etc..,, ie- the correct prop for your boat, wont necessarrily be correct for a different boat of different configuration.. you need to determine if your engine is healthy,, ie- get a compression check.. if that's normal, what your reporting is odd. a lower pitch prop- ie- 17 should be turning faster than a 23. ie- your rpms should go up,,about 200 per inch of change "down in pitch".. you should not be getting the same results.. or worse.. I'd get your engine checked first..
 
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gbalaz

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ImperialVC200 said:
"The boat had a 15.5 17p prop on it when I bought it and it was even worse, probably topping out at 3800RPM"


gb... that engine, "if healthy" should be turning a prop at 4400-4800 rpms in it's "sweet spot". what's that? that's the recommended WOT power band with the correct prop for most Mercruiser engines recommended rpm range is 4400-4800. The size/weight/hull configuration/motor power are all different, the right prop for a 3.0 engine may not be the same as a 4.3 or a 5.0.. etc..,, ie- the correct prop for your boat, wont necessarrily be correct for a different boat of different configuration.. you need to determine if your engine is healthy,, ie- get a compression check.. if that's normal, what your reporting is odd. a lower pitch prop- ie- 17 should be turning faster than a 23. ie- your rpms should go up,,about 200 per inch of change "down in pitch".. you should not be getting the same results.. or worse.. I'd get your engine checked first..
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One thing to note is that the 17p prop that was on it is 1.5" larger dia. We are talking 2 different variables here, change in diameter and change in pitch. While yes the 17 should be turning faster, how does the diameter affect things? Does the reduction in pitch number (23 to 17) but increase in dia by 1.5" affect a whole lot of things?

While I understand every boat is different, that's why i'm here - to ask the experts what prop I should be using. It is typically my wife and I, and the boat is an 18' Crownline with the 4.3 and 1.81 gear ratio. I'm stumped.
 
hwsiii

hwsiii

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I see all of the information mentioned so far in this discussion is about differences in prop diameter and pitch, but nothing has been said about which exact models of props are being compared to each other.

The most important aspect of props for any particular boat and motor combination should always start with blade geometry, for instance just three of the characteristice of concern ( how much and what kind of rake as well as mean width ratio of the blade area and prop cup as well as where the cup is located, either on the blade tips or the trailing edge of the prop) and then focus on diameter and pitch secondarily. For instance, If a semi cleaver prop is chosen for a 21' pontoon boat with a 70 HP motor it will never matter what pitch is used as it will never push a pontoon to any respectable speed with a reasonable prop slip even though there are other props that can do that.

H
 
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gbalaz

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The 15.5dia 17p prop is a quicksilver thunderbolt 5004 stainless steel. The one on it right now is a 14 23p, not sure what brand it is, it appears like it is the stock aluminum prop, no brand marking on it. I can't say for sure if it is the original stock prop or not.
 
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Starcraft5834

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gb. if your sure your engine is ok and capable of reaching it's recommended WOT rpm range,, a 17p is the right direction...Im not familiar with that model CL, if it's heavy and deep V. Michigan Wheel makes a 15x16p 4 blade that might be better yet. I actually have one. (new, in water once) .as a back up to my 15p Solas.. if you have an A1 drive 15 tooth spline. PM me would sell it to you.... the 15p is best for my set up....
 
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MikDee

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gbalaz said:
The 15.5dia 17p prop is a quicksilver thunderbolt 5004 stainless steel. The one on it right now is a 14 23p, not sure what brand it is, it appears like it is the stock aluminum prop, no brand marking on it. I can't say for sure if it is the original stock prop or not.
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A 15" Diam. prop, or bigger, is usually made for a bigger heavier boat, hence your problem! You need a 3 blade 14"X21" prop to help your engine unwind to it's rated 4800 rpm power band. IMO. If tubing, or skiing, a 4 blade 19" pitch would probably do the trick, just fine, as an extra for convenience. Look around for a used one maybe for a spare.
 
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gbalaz

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MikDee said:
A 15" Diam. prop, or bigger, is usually made for a bigger heavier boat, hence your problem! You need a 3 blade 14"X21" prop to help your engine unwind to it's rated 4800 rpm power band. IMO. If tubing, or skiing, a 4 blade 19" pitch would probably do the trick, just fine, as an extra for convenience. Look around for a used one maybe for a spare.
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OK perfect, I was kind of leaning towards a 14 21p. Any particular brand or model number since i've read that there are variances in the cup etc? I'm after a low cost aluminum prop, no SS required.
 
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Chris1956

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Try a Turning Point Hustler, 3 blade. They are as cheap as any other aluminum prop, but are higher performance. I had a boat similar to yours (18' SeaRay w/ 4.3LX/Alpha drive). The higher rake of the Hustler will help carry the bow a bit. I doubt you will make 50MPH though.
 
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