Prop change on my bowrider

[guy48065]

My new-to-me 2000 Bayliner Capris 1850 runs and accelerates great but the rpms are too high. The 4.3L carbureted 190hp motor is rated to 4400-4800 rpm at wot.
I'm not sure I'm hitting wot because I pull it back a bit when I hit 5000rpm.
Current prop is 14.5 x 19 aluminum 3-blade. Looking to try a 14.5 x 21 4-blade. Seems to be a lot of choices at that size, few at 14.5 x 20p.

Make sense?

 

[Stinnett21]

A 21 4 blade will behave like a 23 3 blade, probably too much. I'd try a 21 3 blade. But first, check your tach. I would not expect a carbed 4.3 to be turning a 19 that fast. Something may be off.

 

[jimmbo]

I would try a 3 blade 21. I suspect with the Gearing on a 4.3, it probably came with a 21, but the previous Owner wanted better Hole Shot, and stuck 19 on it

 

[Scott Danforth]

Answer the 6 questions in the prop stickies

 

[StewartL]

Yes, stepping up to a 21P prop makes sense to lower your RPMs. A 4-blade might also improve grip and smoothness. If it over-corrects, a 20P would be the next try check Michigan Wheel or Solas for options.

 

[guy48065]

A 21 4 blade will behave like a 23 3 blade, probably too much. I'd try a 21 3 blade. But first, check your tach. I would not expect a carbed 4.3 to be turning a 19 that fast. Something may be off.

This much difference between 3 & 4 blade props seems excessive--and the Mercury prop selector wouldn't appear to agree.
It recommends a 14.5 x 21 4-blade OR 14.3 x 21 3-blade for my application.

 

[Pmt133]

I had a 19p 3 blade when I was running the 3.0l. I tried a 17p 4 blade prop at the time and picked up 800 rpms... the 3 to 4 blade pitch scale is really dependent on propeller family. Only way to know is to test.

 

[Scott Danforth]

the motor will be fine for a short run to WOT.

still need the answers to all 6 questions in the sticky. https://forums.iboats.com/threads/read-this-first.282907/

 

[guy48065]

the motor will be fine for a short run to WOT.

still need the answers to all 6 questions in the sticky. https://forums.iboats.com/threads/read-this-first.282907/

All answered in OP except #2 which I don't know.

 

[Cortes100]

I know the prop game can get frustrating so I found it best to stick to one brand. Here's my experience with a 4 blade, sort of opposite of what everyone says, but the rpm did not change between the 2.

Similar boat with a 4.5L. Comparing 3 blade to 4 blade. Mercury Blackmax and Spitfire. Both 21P. Across the entire rpm range, both props had the same WOT and MPH. With the 4 blade, better bottom end, less bow lift, and didn't wash out on sharp turns. Overall better performance without sacrificing speed.

Also ran a 19P 4 blade but only on days where we were loaded to the max. With a light load, it would easily hit the limiter at 4950.

 

[Scott06]

My new-to-me 2000 Bayliner Capris 1850 runs and accelerates great but the rpms are too high. The 4.3L carbureted 190hp motor is rated to 4400-4800 rpm at wot.
I'm not sure I'm hitting wot because I pull it back a bit when I hit 5000rpm.
Current prop is 14.5 x 19 aluminum 3-blade. Looking to try a 14.5 x 21 4-blade. Seems to be a lot of choices at that size, few at 14.5 x 20p.

Make sense?

As others have mentioned is the tach accurate? Are you able to hit the rev limiter which should kick in around 5050-5100 rpm. If you cant hit the limiter I would verify the tach is correct before changing props.

I like 4 blades as for how I use my boat it is more suited. But of course this complicates prop selection. Always best if you are new to this to be able to try before you buy either with a marina or prop shop.
if you indeed are hitting 5 k and have throttle to go either a 4 blade 20" like Michigan Vortex or 3 blade 21" would be what I would try.

 

[Scott06]

I know the prop game can get frustrating so I found it best to stick to one brand. Here's my experience with a 4 blade, sort of opposite of what everyone says, but the rpm did not change between the 2.

Similar boat with a 4.5L. Comparing 3 blade to 4 blade. Mercury Blackmax and Spitfire. Both 21P. Across the entire rpm range, both props had the same WOT and MPH. With the 4 blade, better bottom end, less bow lift, and didn't wash out on sharp turns. Overall better performance without sacrificing speed.

Also ran a 19P 4 blade but only on days where we were loaded to the max. With a light load, it would easily hit the limiter at 4950.

The spitfire doesnt have much bite in my experience. I get the same WOT rpm with a 23" spitfire as I do a 21" revolution 4. there is that much slip with the spitfire.

 

[guy48065]

Clear up some shopping confusion for me. I've noticed once you get up in the 135+ hp range that "outboard" and "sterndrive" props look exactly the same, with the insert removed.
If I can also consider large-outboard props it more than doubles my choices.
This observation was also posted here by one of the forums veterans some years ago.

The reason is this: since "everyone sez" a SS prop is a big improvement across the board I'd like to consider going that way. But I haven't got $1000 to spare so I'm looking at used. I've noticed used SS "outboard" props are cheaper than those intended for the Alpha One drive.

 

[Scott06]

Clear up some shopping confusion for me. I've noticed once you get up in the 135+ hp range that "outboard" and "sterndrive" props look exactly the same, with the insert removed.
If I can also consider large-outboard props it more than doubles my choices.
This observation was also posted here by one of the forums veterans some years ago.

The reason is this: since "everyone sez" a SS prop is a big improvement across the board I'd like to consider going that way. But I haven't got $1000 to spare so I'm looking at used. I've noticed used SS "outboard" props are cheaper than those intended for the Alpha One drive.

yes when the Outboards get bigger the hub diameter is the same as stern drive props- you just need to make sure it fits an alpha one.

look on ebay for enertia or revolution 4 props they fit both outboards and stern drives. When I got my new to me boat in 2016 I spent 2-3 years trialing props that I bought off ebay used. Just put a saved search, typically prices are lowest in dead of winter.

Best advice I could give is if this boat is new to you, and you are new to playing with props cut your teeth on aluminum, figure out how you use the boat most of the time then go from there.
Yes you will get better performance out of SS, but it may not matter depending on how you use your boat. if you boat where there is a lot of wood in the water or rocks aluminum is more forgiving for hits..

 

[guy48065]

I've looked at used listings for those because they are the models suggested by the Mercury prop selector. Those models are probably too new and thus too expensive for me. I'm sure I'll be content with a 10 year old model for half the cost.

 

[Chris1956]

The Turning Point props are aluminum and pretty cheap. They share hubs, so for $100 or less you can get a new prop housing, if the pitch it too much.

I ran a 21P 3 blade rapture on my '88 SeaRay 18 footer with a 4.3LX (205HP). It worked real well. The Turning Point Hustlers are nearly as good (IMO) as the Rapture.

I think the correct prop is a 21P, in either 3 or 4 blade. Probably with your max RPM, a 4 blade is best. JMO.

 

[jimmbo]

I've looked at used listings for those because they are the models suggested by the Mercury prop selector. Those models are probably too new and thus too expensive for me. I'm sure I'll be content with a 10 year old model for half the cost.

The Enertia came out 20 years ago. I bought mine in 2005

 

[guy48065]

I'll try this Solas 14x21
Even if it changes nothing it sure is purdy.

I have a question about the workmanship. Everything looks top-shelf except the trailing edge. There's a slight cupping there I'm sure is intentional but on the edge face there's a wire edge left from some hand grinding on the edge top.
Aerodynamically I don't believe there should be any harsh edge.
Should I file/sand off this sharp edge... maybe leave a 1mm bevel at the transition from face to edge?




(Nice to have the photo upload working again!)

 

[Scott06]

I'll try this Solas 14x21
Even if it changes nothing it sure is purdy.

I have a question about the workmanship. Everything looks top-shelf except the trailing edge. There's a slight cupping there I'm sure is intentional but on the edge face there's a wire edge left from some hand grinding on the edge top.
Aerodynamically I don't believe there should be any harsh edge.
Should I file/sand off this sharp edge... maybe leave a 1mm bevel at the transition from face to edge?
View attachment 410645

View attachment 410646

(Nice to have the photo upload working again!)

I wouldnt touch the edge - what you describe is typical

Would expect that to drop your wot rpm a tad

 

[jimmbo]

The Trailing Edge of the Cup, should be Sharp and Abrupt. the Water will separate Cleanly. Any Rounding of the Edge will cause the Water at attempt to Curl around it, and that will increase Drag.