What prop for my set up?

[fastdriver93]

Hello Buddies,
i have trouble to find the right prop for my set up, may be someone can help me out?
I have a 1997 Checkmate Convincor 253, Drive Bravo XR Ratio 1:5, Mercury Racing 500 EFI,
but I have no idea, my guess is a Bravo 1 prop fourblade with 26 pitch, anyone with an advise?
thx
Chris

 

[Glenn Kornett]

Hello Buddies,
i have trouble to find the right prop for my set up, may be someone can help me out?
I have a 1997 Checkmate Convincor 253, Drive Bravo XR Ratio 1:5, Mercury Racing 500 EFI,
but I have no idea, my guess is a Bravo 1 prop fourblade with 26 pitch, anyone with an advise?
thx
Chris

What prop do you have now? What is the rpm and GPS speed at WOT?

 

[fastdriver93]

now I have a 22 Pitch Bravo one fourblade, i do not have these
infos, i only knew that i had 60 kmh at 4500 rpm, that id really too less, hole shot acceleration really to goo do and comparing to my previous set up 500 mpi with 415 hp
and bravo one with ratio 1:65, i had
4800 rpm and 70-71 mph on level 0
and saltwater, thx

 

[fastdriver93]

What prop do you have now? What is the rpm and GPS speed at WOT?

did you got the reply? i am not really sure if I dit it correct

 

[Glenn Kornett]

now I have a 22 Pitch Bravo one fourblade, i do not have these
infos, i only knew that i had 60 kmh at 4500 rpm, that id really too less, hole shot acceleration really to goo do and comparing to my previous set up 500 mpi with 415 hp
and bravo one with ratio 1:65, i had
4800 rpm and 70-71 mph on level 0
and saltwater, thx

First, I would think that a 415 HP 253 Convincor with a 1.5 drive ratio could turn a 24 Bravo, but maybe it would have to be labbed, but other members will answer that have a similar boat to yours. If you had a 1.65 drive ratio and turned it to 4800 rpm, you would need a 28 - 30 pitch prop (with10% - 15% slip) to go 71 mph. That assumes 71 mph is a GPS speed and 4800 is an accurate rpm.
You said that you now have a 22 pitch Bravo 1 and you said it did 60 km/hr which is only 37 mph? It has to be faster so I will assume you meant 60 mph. A 1.5 ratio drive, turning a 22P Bravo at 4500 rpm with 10% slip = 56 mph. I doubt the slip is better than 10%, so either the speedometer is not GPS and it is reading a bit high, or if the 60 mph is an accurate GPS speed then the drive ratio is 1.36 and you have 13% slip with a 22P prop. I think a 502 EFI has an rpm range of 4600 - 5000 rpm, so if your tach is accurate it would require a prop with less pitch?? Are you saying that your holeshot with the 22P is not good enough or that it is better than you need? A 500 EFI Racing has more horsepower, around 470 I believe but a 502 has around 415 HP, so you would not expect a 502 to run as fast as a 500EFI Racing in the same hull. I would think that a 415 HP (healthy motor in good condition) might push a 253 Convincor to mid 60's at best but again I have a lighter 24 ft outboard Checkmate. I had a 23ft Stingray with a 375HP 496 Mag and it ran 67 mphGPS, at 4800 rpm, with a labbed 25P Mirage prop and a 1.5 ratio

 

[fastdriver93]

Thx for all the informations, that is very kind from you, i will answer with more accurate informations, i have a strong running engine and it seems i really have to check out more details, tommorow i will measure the old bravo and its ratio...may be it is only 1.36 and i mixed it up.
the hole shot right now is absolutely tremendous powerful, better than ever before so i guess that i can take a higher pitch, thx first

 

[Glenn Kornett]

Thx for all the informations, that is very kind from you, i will answer with more accurate informations, i have a strong running engine and it seems i really have to check out more details, tommorow i will measure the old bravo and its ratio...may be it is only 1.36 and i mixed it up.
the hole shot right now is absolutely tremendous powerful, better than ever before so i guess that i can take a higher pitch, thx first

Thanks, I would also check the accuracy of your tachometer. If your holeshot is as strong as you say, I understand you saying that you could use more pitch, but that would reduce your rpm out of desired range for that engine. Perhaps your rpm is really closer to 4800 - 5000 rpm now? If so that would make the speed and slip numbers make more sense as well. Between the gear ratio, rpm and mph, one or more of those does not appear accurate since it does not support the math. I am sure you will get to the bottom of it. A 22P Bravo doing 60 mph with a 1.5 ratio is not that far off. Perhaps the rpm is just higher than indicated, or the mph is a bit less. From reading a lot of responses on the Checkmate forum, there similar boats to yours claiming around 60 mph with similar power. Of course there are also much faster ones but with a lot more HP.

 

[fastdriver93]

Thanks, I would also check the accuracy of your tachometer. If your holeshot is as strong as you say, I understand you saying that you could use more pitch, but that would reduce your rpm out of desired range for that engine. Perhaps your rpm is really closer to 4800 - 5000 rpm now? If so that would make the speed and slip numbers make more sense as well. Between the gear ratio, rpm and mph, one or more of those does not appear accurate since it does not support the math. I am sure you will get to the bottom of it. A 22P Bravo doing 60 mph with a 1.5 ratio is not that far off. Perhaps the rpm is just higher than indicated, or the mph is a bit less. From reading a lot of responses on the Checkmate forum, there similar boats to yours claiming around 60 mph with similar power. Of course there are also much faster ones but with a lot more HP.

Tomorrow I will check both ratios the old and the new one, I called today the boatshop from which i purchased the xr drive, he still have the other one out the same boat and set up, they came out a 35 Playboy Cigarette with twin steps, the cigarette had 30 pitch fourblades bravo ones installed, I also the engine out this boat, the ignition box had been recalibrated, so write again soon, thx so much

 

[fastdriver93]

this week i will go to the junkyard
and check weight of the boat

 

[Glenn Kornett]

this week i will go to the junkyard
and check weight of the boat

Not sure if he weight of the old Cigarette with twin 500 EFI's will help you out with much. Do you know the exact horsepower of the engine you installed in your Checkmate and the drive ratio in it now? If so, there are members with similar Checkmates that have posted their WOT speeds and with their current HP levels and you could read those to see if you are in the ballpark.

 

[fastdriver93]

Hi Glenn,
i have now more details
my old set up
415 hp, 1:1:35 bravo 22 fourblade
old max speed 67-71 mph
new set up
470 hp plus, 1:1:65 bravo xr, 22 four blade
speed not sure, cause rpm goes to high without really getting faster, hope that helps, thx

 

[fastdriver93]

Hi Glenn,
i have now more details
my old set up
415 hp, 1:1:35 bravo 22 fourblade
old max speed 67-71 mph
new set up
470 hp plus, 1:1:65 bravo xr, 22 four blade
speed not sure, cause rpm goes to high without really getting faster, hope that helps, thx

Do you think I can use my old drive,
I am not making any holeshots...

 

[Glenn Kornett]

Do you think I can use my old drive,
I am not making any holeshots...

If you have a 1.65 drive, and turn a 22P Bravo to 5000 rpm at 10% - 12% slip the speed should be 56-57 mph.
Let's assume the 500EFI has a rev limiter at 5000 rpm so it will not exceed 5000 rpm (not sure what yours has). In order to run 70 mph with a 1.65 drive ratio, at 5000 rpm and 10 - 12% slip you would need a 28P Bravo prop. That assumes that the engine could turn it at 5000 rpm which I am not sure about.
if you keep the 22P Bravo prop, and use a 1.35 drive ratio, then a 22P Bravo prop should run 68 - 70 mph at 5000 rpm with 10- 12% slip. Again, I do not know what rpm your engine would turn this prop to at WOT. If it turns it higher into the rev limiter you would need more pitch than the 22P and if it turns it 4600 rpm you would likely need less pitch. That is about the best I can do. If I had to guess, I believe if this Checkmate really has 470 HP, it should run a bit over 70 mph, perhaps more like 73 mph with me guessing. If the engine could push it to 73 mph then you would need a 24P Bravo with a 1.35 drive ratio or a 29 - 30P Bravo with a 1.65 drive ratio but you have to be able to turn that prop at 5000 rpm which again I do not know for certain if you will. All those values assume a prop slip of 10% - 12%.
I hope some other members with similar boats and power chime in to give us more real world results.

Good Luck,
Glenn

 

[fastdriver93]

If you have a 1.65 drive, and turn a 22P Bravo to 5000 rpm at 10% - 12% slip the speed should be 56-57 mph.
Let's assume the 500EFI has a rev limiter at 5000 rpm so it will not exceed 5000 rpm (not sure what yours has). In order to run 70 mph with a 1.65 drive ratio, at 5000 rpm and 10 - 12% slip you would need a 28P Bravo prop. That assumes that the engine could turn it at 5000 rpm which I am not sure about.
if you keep the 22P Bravo prop, and use a 1.35 drive ratio, then a 22P Bravo prop should run 68 - 70 mph at 5000 rpm with 10- 12% slip. Again, I do not know what rpm your engine would turn this prop to at WOT. If it turns it higher into the rev limiter you would need more pitch than the 22P and if it turns it 4600 rpm you would likely need less pitch. That is about the best I can do. If I had to guess, I believe if this Checkmate really has 470 HP, it should run a bit over 70 mph, perhaps more like 73 mph with me guessing. If the engine could push it to 73 mph then you would need a 24P Bravo with a 1.35 drive ratio or a 29 - 30P Bravo with a 1.65 drive ratio but you have to be able to turn that prop at 5000 rpm which again I do not know for certain if you will. All those values assume a prop slip of 10% - 12%.
I hope some other members with similar boats and power chime in to give us more real world results.

Good Luck,
Glenn

Do you think I can swap the xr to the standard drive, cause than I have the 1:1.35 ratio which will be good for the performance but I am not sure if it is strong enough for normal purose, no holeshots and only sometimes speeding to the max?

 

[Glenn Kornett]

Do you think I can swap the xr to the standard drive, cause than I have the 1:1.35 ratio which will be good for the performance but I am not sure if it is strong enough for normal purose, no holeshots and only sometimes speeding to the max?

An XR drive is stronger and if you have 470 HP, I would think that it would last longer. People say that due to less teeth, the 1.65 ratio is stronger than the 1.5 ratio, but I don't really know if that is the case. People also say that a 1.65 gear ratio, turning a larger prop at a lower rpm is more efficient, but again I can't verify that but it is often said. If it was my boat, before I went to the trouble of swapping drives, I would just look for a 26, 28 or 30 pitch Bravo prop to try on the 1.65 drive and see what rpm the prop will turn and then decide which is the next prop to test. Does your 500 EFI have a rev limiter? If so what rpm does it come in at? Did you feel the rev limiter with the 22P prop on the 1.65 drive?

 

[Glenn Kornett]

An XR drive is stronger and if you have 470 HP, I would think that it would last longer. People say that due to less teeth, the 1.65 ratio is stronger than the 1.5 ratio, but I don't really know if that is the case. People also say that a 1.65 gear ratio, turning a larger prop at a lower rpm is more efficient, but again I can't verify that but it is often said. If it was my boat, before I went to the trouble of swapping drives, I would just look for a 26, 28 or 30 pitch Bravo prop to try on the 1.65 drive and see what rpm the prop will turn and then decide which is the next prop to test. Does your 500 EFI have a rev limiter? If so what rpm does it come in at? Did you feel the rev limiter with the 22P prop on the 1.65 drive?

I used to own a 230SX Stingray with a 496 Mag and Bravo 1 drive. That engine was rated at 375 HP. You could also order a 496 Mag HO which was rated at 425 HP. If you ordered the 425HP version, Mercury only sold it with an XR drive. Anytime the HP went much over 400 HP, Mercury usually sold them with an XR drive because they were concerned with the reliability of the standard Bravo 1 drive when you put that much HP and torque through it.

 

[fastdriver93]

Hi Glenn, thx gor your support,
I have 30 Pitch props on another Boat and my Idea is to start to test with this one, the boat shop is also having an used 28 left hand, so i can figure it out and keep you informed, what is going on, thx s lot

 

[Glenn Kornett]

Hi Glenn, thx gor your support,
I have 30 Pitch props on another Boat and my Idea is to start to test with this one, the boat shop is also having an used 28 left hand, so i can figure it out and keep you informed, what is going on, thx s lot

I am not 100% certain, but I think you can use the left hand 28P prop for a test by running the control lever in reverse, provided the cable produces full throttle in both the forward and reverse position but I would check with someone that knows more about Bravo Drives than me on that. I think that would reverse the thrust direction on the top gears but for testing purposes to determine the WOT rpm and GPS speed I think it is fine.

 

[Glenn Kornett]

I am not 100% certain, but I think you can use the left hand 28P prop for a test by running the control lever in reverse, provided the cable produces full throttle in both the forward and reverse position but I would check with someone that knows more about Bravo Drives than me on that. I think that would reverse the thrust direction on the top gears but for testing purposes to determine the WOT rpm and GPS speed I think it is fine.

If I had to guess I would think that a 30P is going to be a bit too much pitch but you never know until you try. The difference between 1.36 and 1.65 is about 20%, so if you turned a 22P x 1.20 = 26.4P with a 1.36 drive, then if you switched the drive ratio to 1.65 it would theoretically turn a 26.4P prop to the same rpm. Of course you have more HP as well so my guess would be a 28 or 30P but you have to try it to find out.

 

[fastdriver93]

Hi Glenn
thx so much, i have to winterize the boat soon and I could not chevked it out this time, but next spring I keep you informed, thx for all your support, you a very helpful member here and you have a lot of knowledge, cause otherwise we had a big discussion here....
thx