Leaving Power on the Table

[Chestah Cheetah]

Got a slight problem here that just might help me pick up a couple MPH once resolved.

2006 Howard Bullet
2006 525EFI With Whipple Stage 1 ECM Program
90 Hours on Motor
Teague Platinum Drive with Imco Standard Lower 1.36 Gears
Bravo 28P and Bravo 26P
91 Octane Fuel
Top Speed, with either Prop = 79MPH

With either prop, the motor only winds up to 4900RPM. This is our wall. The guess is we need to swap the gears to 1.50. Maybe try a 24P to see what RPM range I get out of it? What are some thoughts on why we can't get full RPM?

 

[shippingguy]

Got a slight problem here that just might help me pick up a couple MPH once resolved.

2006 Howard Bullet
2006 525EFI With Whipple Stage 1 ECM Program
90 Hours on Motor
Teague Platinum Drive with Imco Standard Lower 1.36 Gears
Bravo 28P and Bravo 26P
91 Octane Fuel
Top Speed, with either Prop = 79MPH

With either prop, the motor only winds up to 4900RPM. This is our wall. The guess is we need to swap the gears to 1.50. Maybe try a 24P to see what RPM range I get out of it? What are some thoughts on why we can't get full RPM?

I think you have this turned around. If you stayed with the 1.36 you would want to run the 24 and I bet the RPM's will go up(the 26 and 28 are too big for the 1.36). If you switch to the 1.50 you would still run the 26 and 28 and would increase your RPM and speed possibly.

 

[BDMar]

Assuming everything is mechanically sound, we would never run 1.36 gears with that power level. You will have a better performing propeller and the mechanical advantage of lower gears with 1.50 gear ratio.

 

[Chestah Cheetah]

I think you have this turned around. If you stayed with the 1.36 you would want to run the 24 and I bet the RPM's will go up(the 26 and 28 are too big for the 1.36). If you switch to the 1.50 you would still run the 26 and 28 and would increase your RPM and speed possibly.

I should have clarified. Stick with the 1.36 gears and run a Bravo 24P or change to 1.50 gears and run the Bravo 28P.

Assuming everything is mechanically sound, we would never run 1.36 gears with that power level. You will have a better performing propeller and the mechanical advantage of lower gears with 1.50 gear ratio.

This is what I am figuring, just wanted to see if there were any other possible theories as to the RPM loss. Everything else seems to be running very well.

 

[shippingguy]

I should have clarified. Stick with the 1.36 gears and run a Bravo 24P or change to 1.50 gears and run the Bravo 28P.



This is what I am figuring, just wanted to see if there were any other possible theories as to the RPM loss. Everything else seems to be running very well.

Got it!

 

[Enen]

Cheapest solution will be a smaller prop. You are looking at a couple of G's for gears, and a couple hundred for a prop.

 

[Don Johnson]

Assuming everything is mechanically sound, we would never run 1.36 gears with that power level. You will have a better performing propeller and the mechanical advantage of lower gears with 1.50 gear ratio.

Exactly.

Did this boat used to have big power? If not don't understand why it was geared 1.36. Switching to 1.5 gear drive and propped to pull red line will make the boat much more spirited and likely faster top speed.

 

[fishing fool]

Are you hitting a rev limiter? That would stop your rpm's at the same spot with both props.

 

[Chestah Cheetah]

Cheapest solution will be a smaller prop. You are looking at a couple of G's for gears, and a couple hundred for a prop.

True. I fear I will not get the top end speed numbers out of a 24 however.

Exactly.

Did this boat used to have big power? If not don't understand why it was geared 1.36. Switching to 1.5 gear drive and propped to pull red line will make the boat much more spirited and likely faster top speed.

I believe the previous owner was planning on running bigger power so he installed the Teague Drive with 1.36 gears. It was never rigged. I had a 525EFI installed along with a complete re-rig of the whole boat.

Are you hitting a rev limiter? That would stop your rpm's at the same spot with both props.

Not hitting the rev limiter.

 

[fishing fool]

True. I fear I will not get the top end speed numbers out of a 24 however.



I believe the previous owner was planning on running bigger power so he installed the Teague Drive with 1.36 gears. It was never rigged. I had a 525EFI installed along with a complete re-rig of the whole boat.



Not hitting the rev limiter.

Are you 100% sure. And also check to see it the tach is right. I had a tach in a race car and switched it out and lost 1000 rpm. Found out it was the tach.

 

[Chestah Cheetah]

Are you 100% sure. And also check to see it the tach is right. I had a tach in a race car and switched it out and lost 1000 rpm. Found out it was the tach.

99.9% sure. I have a Vessel View 4.

 

[Ziggy]

Are you running mufflers?
I'm finding out that someone with an identically rigged boat to mine is running 5-6 mph faster than mine without mufflers.
I'm also not getting more than 4900rpm either.......on either a 24 or 26 merc prop.
If I'm lucky enough to get one more trip in this year I'll be pulling my mufflers and seeing what difference it makes.

 

[Chestah Cheetah]

Are you running mufflers?
I'm finding out that someone with an identically rigged boat to mine is running 5-6 mph faster than mine without mufflers.
I'm also not getting more than 4900rpm either.......on either a 24 or 26 merc prop.
If I'm lucky enough to get one more trip in this year I'll be pulling my mufflers and seeing what difference it makes.

No mufflers here. Just external rubber flappers.

 

[STV_Keith]

Take it to Brian (BDMar) at B&D and let him look it over. If he doesn't find anything, he's about the best drive guy there is down there...and can swap those gears for you. There's a real art to setting the gears up right and he's REAL good at that.

 

[HALLETT BOY]

Are you running mufflers?
I'm finding out that someone with an identically rigged boat to mine is running 5-6 mph faster than mine without mufflers.
I'm also not getting more than 4900rpm either.......on either a 24 or 26 merc prop.
If I'm lucky enough to get one more trip in this year I'll be pulling my mufflers and seeing what difference it makes.

These concerned Lake Mojave rangers don't like noise ...this is WITH mufflers , Imco Gattlins .

 

[Ziggy]

These concerned Lake Mojave rangers don't like noise ...this is WITH mufflers , Imco Gattlins .

I remember reading your story about that...[emoji16]

 

[Chestah Cheetah]

Take it to Brian (BDMar) at B&D and let him look it over. If he doesn't find anything, he's about the best drive guy there is down there...and can swap those gears for you. There's a real art to setting the gears up right and he's REAL good at that.

I'm in San Francisco, nowhere near B&D. I have heard he does great work however.

I do have a 30 year veteran high performance mechanic here locally that is phenomenal. At the moment, I am attempting to inject a bit of boating content and gather some opinions. :thumbup:

 

[BUSTI]

I own a 25' Bullet CBR and run a 1.5:1 lower with a Ron Hill 26 SL4. I would change your lower and keep a 26P prop. The midrange acceleration will be much better. I would think that motor is struggling to move that boat with those gears. You actually may not pick up much speed but the over all performance will be much better with the engine not lugging.

Don't expect that boat to be much more than 80 without big power.

 

[prosthogod]

Get a new motor that turns 6200 RPM.Problem solved.

 

[Enen]

Hey Chesta, just throw a whipple on that 525 and call it good.

 

[Chestah Cheetah]

I own a 25' Bullet CBR and run a 1.5:1 lower with a Ron Hill 26 SL4. I would change your lower and keep a 26P prop. The midrange acceleration will be much better. I would think that motor is struggling to move that boat with those gears. You actually may not pick up much speed but the over all performance will be much better with the engine not lugging.

Don't expect that boat to be much more than 80 without big power.

I'm only expecting that elusive 80MPH. At 79MPH now with this setup, fully loaded. In the end, I'm sure I'll end up with new 1.50 gears or simply swap the whole drive for a stock XR with 1.50 already installed.

Get a new motor that turns 6200 RPM.Problem solved.

Hey Chesta, just throw a whipple on that 525 and call it good.

Looks like I just found two new boat wrench buddies. When are you guys coming over with my new Whippled motor? Or I'll just take one of your Boostpower mills. Already geared for it!

 

[lake p.a.l.]

Or just sell all of that stuff and bolt on a couple of 400's rolleyes

 

[BDMar]

I usually give advice and let it be, but I really think you will be extremely happy with a gear change. I built a 509 CI 625 HP engine for a Hallett 240 a while ago. We knew it had 1.36 gears, but the customer was at his budget. A year later we changed to 1.50 gears and the boat picked up 7 MPH and the acceleration was way better. It ran 5600 with both gear ratios, but the prop needed for the 1.36 gears did not have enough thrust to get the boat up and moving.

Cost to change gears (assuming XR) should be about $1300.00 to $15.00. It will be more if it's a Bravo One. XR changes the ratio in the lower (2 gears) and Bravo One changes ratio in the uppper (3 gears) and more labor.

Edit: A Bullet wants more prop to carry the boat.

 

[BUSTI]

I'm only expecting that elusive 80MPH. At 79MPH now with this setup, fully loaded. In the end, I'm sure I'll end up with new 1.50 gears or simply swap the whole drive for a stock XR with 1.50 already installed.

Just change the gears and be done with it. The motor really be in a better place with the advantage the gears give you.