Prop Help on 3.0 Alpha 1

[Moose_25_2500]

I have a 2002 bayliner 19' 1950 capri classic bowrider - 2091 lbs with a 3.0 Mercruiser alpha 1. gear ratio 2.0. Current prop is a 14.25 x 21p aluminum (original) My tach was broken last year and I replaced it and I am getting ready to drop it in the water in a few weeks. I will report all my numbers when I do. Pretty sure I need to drop the pitch down to 19. I had issues with getting up on plane last year with heavy loads and watersports. Plus I think my 12 year old motor cannot handle the stock prop anymore. So since I need a backup anyway and want to help get on plane quicker I am going to purchase a 19p aluminum before I drop it in the water.
My question is there a difference between a 14 x 19p and a 14.5 x 19p and what type of prop woulkd be best for my motor? Solas Amita, Michigan Match, Hustler, etc ?
Thanks

 

[steelespike]

Re: Prop Help on 3.0 Alpha 1

I think a 19 will work well. Diameter is a secondary consideration A 19 should act like a 19.The slightly larger diameter might have a little better hole shot or then again might put more load on the motor.If the prop is intended for your boat it should work.
I like the Solas props and they say the Rubex with the removable hub comes with the hardware.
The Hustler is said to deliver close to stainless performance.

 

[fishrdan]

Re: Prop Help on 3.0 Alpha 1

issues with getting up on plane last year with heavy loads and watersports.

You may want to look into getting a 4 blade prop as they help a LOT with getting up on plane, holeshot. (18P 4-blade???)

 

[Moose_25_2500]

Re: Prop Help on 3.0 Alpha 1

I think a 19 will work well. Diameter is a secondary consideration A 19 should act like a 19.The slightly larger diameter might have a little better hole shot or then again might put more load on the motor.If the prop is intended for your boat it should work.
I like the Solas props and they say the Rubex with the removable hub comes with the hardware.
The Hustler is said to deliver close to stainless performance.

Thanks for the info. The Solas props are the best priced and the 14.5 dia also seems to be the standard. Only Mich Match has the 14 dia

 

[Moose_25_2500]

Re: Prop Help on 3.0 Alpha 1

You may want to look into getting a 4 blade prop as they help a LOT with getting up on plane, holeshot. (18P 4-blade???)

Thanks Fishrdan. I have been looking at the 4 blades and lots of people on here love them but, I am a little apprehensive about pulling the trigger on one until I get my performance numbers back. Thats why I was going to get the 19p alum 3 blade and see where the numbers come in. I dock my boat all summer and can change the prop on the lake in some shallow water if I had too. Do you think the 18p 4 blade is the right move? I was thinking about puttting a flat trim tab anode on just incase I change to a 4 blade

 

[Starcraft5834]

Re: Prop Help on 3.0 Alpha 1

You may want to look into getting a 4 blade prop as they help a LOT with getting up on plane, holeshot. (18P 4-blade???)

+1 4 blade for sure....18p max. JMHO

 

[fishrdan]

Re: Prop Help on 3.0 Alpha 1

and see where the numbers come in.

Do you think the 18p 4 blade is the right move?

I was thinking about puttting a flat trim tab anode on just incase I change to a 4 blade

It's best to get performance numbers before buying a new prop. It's a guess if the 18P would be right without numbers. I'm using an 18P Alpha4 with my 140HP (3.0L) and love it, but your boat may act different, load, hull design, etc....

I just ground down my trim tab to clear the 4 blade prop, though you would need the prop to do so. Think it was about 1/2" that was taken off, little dip in the leading edge.

 

[Moose_25_2500]

Re: Prop Help on 3.0 Alpha 1
It's best to get performance numbers before buying a new prop. It's a guess if the 18P would be right without numbers. I'm using an 18P Alpha4 with my 140HP (3.0L) and love it, but your boat may act different, load, hull design, etc....
I just ground down my trim tab to clear the 4 blade prop, though you would need the prop to do so. Think it was about 1/2" that was taken off, little dip in the leading edge.

Update: So I bought an Alpha 4 18" pitch 4 blade Aluminum prop and here are my numbers from yesterday.

2001 Bayliner 3.0 Mercurser Alpha 1 Gen 2 --- 2.0 Gear Ratio
2100 Lbs Boat + 600 lbs people and gear. (2 adults and 2 children)
WOT - 4000 RPM
Top Speed - 36 MPH trimmed out by GPS
Up on Plane in 4-5 Seconds
Cruising speed 25-28 mph - 2800-3000 rpm

I wish I had the numbers to compare to since my Tach was broken last year....all I can say is that with the same loading my 14.25 x 21p mich wheel took 10+ seconds to plane and a top speed of 38 MPH.

I love this prop and cannot believe how fast it planes and gets to 30 MPH

I am surprised I am still below the 4200-4600 max rpm ar WOT

Do you think I could go to a 17"pitch 4 blade? not that I am in any rush....pretty happy with these numbers

 

[fishrdan]

Speed sounds correct for an 18P prop at the WOT RPM for a Mercruiser 3.0L, that's about the speed my 140HP is running at 4500-4600RPM.

Are you sure your tach is correct?

 

[Moose_25_2500]

No I am not sure if the Tach is working properly. The rpms seemed low for my 135 HP but, I do not have anything else to compare to. I have read other posts where people are running 17p 4 blade props. I maxed out at 4000rpms and 36 mph but I got many readings through out the weekend at 34 to 35 mph at 3800 - 3900 rpms

Also the tach is new and I had to run a new sender wire to the coil to make it work. The old wire was either broken or messed up in the harness somewhere.

 

[jestor68]

36 mph with your gear ratio, 18 pitch and using a 10% slip works out to 4693 rpm.

You can't go 36 mph at 4000 rpm.

Check the settings on the back of the tach to insure it's set for a 4 cylinder motor.

 

[Starcraft5834]

Update: So I bought an Alpha 4 18" pitch 4 blade Aluminum prop and here are my numbers from yesterday.

2001 Bayliner 3.0 Mercurser Alpha 1 Gen 2 --- 2.0 Gear Ratio
2100 Lbs Boat + 600 lbs people and gear. (2 adults and 2 children)
WOT - 4000 RPM
Top Speed - 36 MPH trimmed out by GPS
Up on Plane in 4-5 Seconds
Cruising speed 25-28 mph - 2800-3000 rpm

I wish I had the numbers to compare to since my Tach was broken last year....all I can say is that with the same loading my 14.25 x 21p mich wheel took 10+ seconds to plane and a top speed of 38 MPH.

I love this prop and cannot believe how fast it planes and gets to 30 MPH

I am surprised I am still below the 4200-4600 max rpm ar WOT

Do you think I could go to a 17"pitch 4 blade? not that I am in any rush....pretty happy with these numbers

your in the right ballpark...make sure your tach is working correctly...before you change anything... assuming your tach is working correctly,, going down in pitch will (should) bring your WOT up about 200

 

[Moose_25_2500]

I am pretty sure the tach is set to 4 cylinder but, will double check and report back. even if it is I will re-set it and test agian. I have heard that by re-setting the cylinder adjustment can somtimes get the tach working properly. No idea if thats true or not. thanks for the help

 

[Starcraft5834]

anytime..... enjoy that 4 blade..... they are sweet! 4 blades are better than 3...........

 

[MikDee]

I thought you were going with the Solas Amita 4 blade? I think that might have worked better?

 

[Moose_25_2500]

I thought you were going with the Solas Amita 4 blade? I think that might have worked better?

I was going to until I read some negative reviews and ended up getting the Alpha 4 for $20 cheaper off ebay. Either way its 10 times better than the 21p 3 blade I was running.

LOVE THE 4 BLADE

 

[Lager]

We all assume that that the measurements on the prop are correct, meaning 19 inch is the same as another prop thats measured at 19 inch. and will deliver the same performance, but it really does not.One prop might had the correct angle for 19 inch pitch but a small surface area, another might have the 19 in pitch but a large surface area. Same pitch, but which one will push your boat to faster speed and create a bigger load on your engine, thus reducing RPMs.
This is why comparing props is not just about pitch and diameter, buts its also about blade shape and design. Dont assume a change in pitch will correspond correctly to the math equation every time.

 

[steelespike]

Boat can't go 36 at 4000 rpm. if we guess 13% slip 18" prop 36 mph = 4800 rpm.
If you think about it a 4-5 second hole shot doesn't really go with a setup that only makes 4000 rpm.

 

[Moose_25_2500]

Boat can't go 36 at 4000 rpm. if we guess 13% slip 18" prop 36 mph = 4800 rpm.
If you think about it a 4-5 second hole shot doesn't really go with a setup that only makes 4000 rpm.

I agree and was back out today with the same results. Tach setting was right at 4 cyl and played with the adjustment to make sure it was in the right position... I hit 37 mph at 4000 rpm again.....not sure what to do to get the tach working properly. maybe try another one and see if it works?

 

[steelespike]

You may be able to borrow a shop tach. Did you operate the switch a few times to clean the contacts?
If it is actually set on a 6 cylinder its might produce those numbers.