20.5 Ft Bowrider Prop Choice

[akcooper9]

Hey guys, went to put the new prop on and noticed the lock washer for the flow torq II wouldnt work. Can you guys point in the right direction as far as what lock washer I need to run this prop?

 

[akcooper9]

I decided to just press the old hub out and run both props with a flo torq II setup. Heading out Saturday for the first trip of the season. Will report back..I starting off off with the 19P

 

[akcooper9]

Spent the day on the water. It was to rough for a wide open run but the 19P holds plane much better at a lower speed. It also brings the boat out of the hole much better. Acceleration is excellent. As of right now, the only thing I wonder is if a smaller diameter prop would make the hole shot better AND now a 4 blade would work

 

[akcooper9]

Finally had a chance to get a speed test with the GPS on some glass. I was able to turn 5000 RPMS at 48 MPH. This looks to be about 14% prop slip.

So now what?

 

[akcooper9]

Bringing this thread back from the dead. Still running the Mirage 19P but found a Rev 4 48-857024A46 17P locally in great shape for 300 bucks.

Any thoughts or input on picking this up? I do like the 19P 3 blade but as time goes on I'd like more hole shot especially when we take a few extra adults with us. Top speed with a properly adjusted outdrive trim up is close to 55 MPH. Plenty fast for me. Is the 17P 4 blade the answer?

 

[jimmbo]

If you can, try an Enertia. It is a prop that can offer quicker Hole Shot, as well as better top speed

 

[porscheguy]

I’ve got a rev4, a mirage+, and an enertia. My boat is a foot shorter and maybe weighs 300-400 lbs less than yours due to mine being a 4.3.

my enertia mostly stays on the shelf. This summer I’ve been running the rev4 a lot even though it’s not my favorite prop. It’s an excellent stern lifting prop that allows a lot of trim adjustment on the outdrive. I’m on the Chesapeake bay which can get very choppy so it’s nice to be able to really force the nose down which the rev4 does well.

if I could always run in smoother conditions I’d use my mirage plus. The mirage lifts the bow a lot. It will not blow out at all. The problem with the bow lift is that it’s great for going fast, but when it gets choppy (and that’s guaranteed out here) it’s hard to force the bow down.

The question i have is are you trying to improve holeshot to minimize the time the time the bow is pointing up in the air? Because on shorter boats, the mirage will make the bow reach for the stars.

If you shop around, you can get some Bennett trim tabs for not much more than that prop. They can get you on plane faster without the loss of top end performance like you’d have with a lower pitch prop.

 

[akcooper9]

I’ve got a rev4, a mirage+, and an enertia. My boat is a foot shorter and maybe weighs 300-400 lbs less than yours due to mine being a 4.3.

my enertia mostly stays on the shelf. This summer I’ve been running the rev4 a lot even though it’s not my favorite prop. It’s an excellent stern lifting prop that allows a lot of trim adjustment on the outdrive. I’m on the Chesapeake bay which can get very choppy so it’s nice to be able to really force the nose down which the rev4 does well.

if I could always run in smoother conditions I’d use my mirage plus. The mirage lifts the bow a lot. It will not blow out at all. The problem with the bow lift is that it’s great for going fast, but when it gets choppy (and that’s guaranteed out here) it’s hard to force the bow down.

The question i have is are you trying to improve holeshot to minimize the time the time the bow is pointing up in the air? Because on shorter boats, the mirage will make the bow reach for the stars.

If you shop around, you can get some Bennett trim tabs for not much more than that prop. They can get you on plane faster without the loss of top end performance like you’d have with a lower pitch prop.

I did some reading on the enertia and thats not what Im looking for. I agree to the mirage will flat haul the mail when its smooth. The only time I notice big bow lift is when I have two adults on the back bench and towing something.

If I could get better hole shot, towing performance etc and still bang 50+MPH with the Rev 4 I would be a happy camper.

 

[porscheguy]

Did you ever determine your gear ratio? It sounds like you’ve got 1.47 gearing. The speeds you’ve attained aren’t really possible with 1.62 gearing because you would have negative slip, which definitely isn’t possible.

50mph and a 1.47 ratio puts you at 8.5% slip which is possible with a rev4.

Make sure you get the correct hub kit for the rev4. It’s a very heavy prop. The hub kit will contain an extra bushing to provide a bit more support. It’s supposed to help reduce the stress of surfacing on high mounted drives. On an alpha1, it makes it shift into gear easier.

 

[akcooper9]

Did you ever determine your gear ratio? It sounds like you’ve got 1.47 gearing. The speeds you’ve attained aren’t really possible with 1.62 gearing because you would have negative slip, which definitely isn’t possible.

50mph and a 1.47 ratio puts you at 8.5% slip which is possible with a rev4.

Make sure you get the correct hub kit for the rev4. It’s a very heavy prop. The hub kit will contain an extra bushing to provide a bit more support. It’s supposed to help reduce the stress of surfacing on high mounted drives. On an alpha1, it makes it shift into gear easier.

I've got 1.62 gears. Its been a few years since Ive checked the speedo accuracy with the GPS. With the Mirage I can run up to 4900 RPMS with out issues. I'd need to do another speed to via GPS to nail down the speed though.

If I can run 40 plus with the Rev4 I'd be happy. I did talk with Ken at Prop Gods and he recommended the SFS4.

 

[akcooper9]

Make sure you get the correct hub kit for the rev4. It’s a very heavy prop. The hub kit will contain an extra bushing to provide a bit more support. It’s supposed to help reduce the stress of surfacing on high mounted drives. On an alpha1, it makes it shift into gear easier.

BTW, this is the hub kit I have. Is this what you are talking about?

 

[porscheguy]

No. Look for 835257K6 (mercury) or 835257Q6 (Quicksilver). This kit contains a “forward bushing” 856163Q1, and supposedly a hardened thrust washer. Honestly, you can buy just the forward bushing and insert it into the standard hub kit you’ve already got. You’re also supposed to torque it down to 90-100lb-ft but it’s not really necessary. The standard torque rating is fine. That forward bushing improves the shift feel on any prop so I use it with all of mine.

 

[akcooper9]

No. Look for 835257K6 (mercury) or 835257Q6 (Quicksilver). This kit contains a “forward bushing” 856163Q1, and supposedly a hardened thrust washer. Honestly, you can buy just the forward bushing and insert it into the standard hub kit you’ve already got. You’re also supposed to torque it down to 90-100lb-ft but it’s not really necessary. The standard torque rating is fine. That forward bushing improves the shift feel on any prop so I use it with all of mine.

Im pretty sure I have the bushing but Ill check when I get home tonight. For now, I've held off on the 17P Rev 4.

Is there any reason NOT to get it?

 

[porscheguy]

If it’s in good shape, @ $300 I’d buy it. If you don’t like it, you can sell it. If not here, probably on the hull truth. The rev4 retails at almost $800 brand new these days.

You won’t know if you like it until you use it. I would definitely buy it over a powertech.

 

[QBhoy]

HI
just reading this post is fascinating to me. Must have missed it first time.
Not one for doubting you AK, but it doesn’t make total sense to me.
Mate you sure you have a 1.62 ratio ? The numbers seem crazy.
More than that. If you are now thinking of a 17” (all be it a big diameter rev 4), you will be crazy under propped at that ratio.
I have a similar performance hull (perhaps a little more tweaked towards performance maybe) and a 5.0 mpi with cam and exhausts, all be it (for all its worth. Not sure it’s worth much as the exhausts only make a slight difference at wot and cost load on the engine via alternator to keep them open. The cam is likely only efficient at wot because the fuelling isn’t well suited down the rpm) the boat is about 1400 kgs. But she has a 1.47 ratio.
Anyway. Any 19” of any sort prop will easily hit the limiter at 5150 rpm in seconds. A 21” laser 2 and even and enertia...also a ballistic will also occasionally hit the limiter if running light with a clean hull at start of season. Best she has ever ran was about 66.7 mph gps but usually about 64/65 with gear (or bow seats even haha) on board.
If you have a fast hull and the 5.0 mpi with a 1.62...surely to god a 17” will be rocket ship out the hole but will hit the limiter in a couple of seconds. Will be so inefficient too.

 

[akcooper9]

HI
just reading this post is fascinating to me. Must have missed it first time.
Not one for doubting you AK, but it doesn’t make total sense to me.
Mate you sure you have a 1.62 ratio ? The numbers seem crazy.
More than that. If you are now thinking of a 17” (all be it a big diameter rev 4), you will be crazy under propped at that ratio.
I have a similar performance hull (perhaps a little more tweaked towards performance maybe) and a 5.0 mpi with cam and exhausts, all be it (for all its worth. Not sure it’s worth much as the exhausts only make a slight difference at wot and cost load on the engine via alternator to keep them open. The cam is likely only efficient at wot because the fuelling isn’t well suited down the rpm) the boat is about 1400 kgs. But she has a 1.47 ratio.
Anyway. Any 19” of any sort prop will easily hit the limiter at 5150 rpm in seconds. A 21” laser 2 and even and enertia...also a ballistic will also occasionally hit the limiter if running light with a clean hull at start of season. Best she has ever ran was about 66.7 mph gps but usually about 64/65 with gear (or bow seats even haha) on board.
If you have a fast hull and the 5.0 mpi with a 1.62...surely to god a 17” will be rocket ship out the hole but will hit the limiter in a couple of seconds. Will be so inefficient too.

The out drive is a merc reman unit with 1.62 part number stamped on it.

I passed on the 17P 4 blade as like you said, I suspect it would be to much.

We leave Sunday for a 7 days at the lake. I bet I come back with some new numbers for Revs and Speed

For this trip, the 3 blade with do just fine as it has the past 4 years

 

[akcooper9]

Quick update. Boat is running good. Turned 4900 rpms at 51 mph per gps. Fuel tank full, Bimini up, wife and two kids up in the bow.

Assuming the reman Merc out drive isn't miss marked with incorrect gears and is really 1.62, this hill with a 15 degrees deadrise is running 51 mph with. 3 blade 19p mirage prop.

what other info do you all need?

 

[QBhoy]

Quick update. Boat is running good. Turned 4900 rpms at 51 mph per gps. Fuel tank full, Bimini up, wife and two kids up in the bow.

Assuming the reman Merc out drive isn't miss marked with incorrect gears and is really 1.62, this hill with a 15 degrees deadrise is running 51 mph with. 3 blade 19p mirage prop.

what other info do you all need?

Stick to a 3 blade. Those numbers are good, but could be better. I honestly think you should try an enertia or even a tempest plus. I was amazed at how good the tempest was on my new boat. It does however have a rather large diameter and a bit clunky going into gear.
The enertia will be well suited to this boat and I think you may even find you could go to a 20”. The enertia manages to lift a hull that far out the water that I’ve found it gains rpm at the top end over any other fast prop I’ve tried of the same pitch. With your similar to mine performance hull and with a pad. It will be well suited. It also doesn’t seem to suffer out the hole either. Very similar to the excellent laser 2 I have, but a couple mph quicker top end and almost bizarrely slightly better cruising rpm and form. If you can get a shot of one you won’t be disappointed. They come in 1” increments for fine tuning too. One of the few that do.
Best of luck. Oh and I’m aware mirage are great things but also big and heavy with a large diameter. Not so kind to the Alpha one straight cut system.

 

[porscheguy]

Quick update. Boat is running good. Turned 4900 rpms at 51 mph per gps. Fuel tank full, Bimini up, wife and two kids up in the bow.

Assuming the reman Merc out drive isn't miss marked with incorrect gears and is really 1.62, this hill with a 15 degrees deadrise is running 51 mph with. 3 blade 19p mirage prop.

what other info do you all need?

That’s actually very good. If you plug your data into a prop slip calculator, you’re at 6.25% slip. That’s about what I see on my boat which is 19.5’ and uses a 21p mirage plus. I’ve got 1.84 gearing and a 4.3. I see 49mph running by myself.

As far as 19p props go, with your current ratio, and rpm limit of 4900, the maximum theoretical top speed you can see is 54mph. And that assumes a 0% slip which isn’t really possible. What is the redline on that engine? 4800? 5000?

 

[QBhoy]

That’s actually very good. If you plug your data into a prop slip calculator, you’re at 6.25% slip. That’s about what I see on my boat which is 19.5’ and uses a 21p mirage plus. I’ve got 1.84 gearing and a 4.3. I see 49mph running by myself.

As far as 19p props go, with your current ratio, and rpm limit of 4900, the maximum theoretical top speed you can see is 54mph. And that assumes a 0% slip which isn’t really possible. What is the redline on that engine? 4800? 5000?

It will limit at 5150 exactly. Mine does it easily with the prop on it. Same engine. The recommended is 4600-5000, but I’ve found it really comes on song at about 4800