150 Pro XS SLOWER than regular 150?

[mikesxpress]

While the hulls in your example are the same, the addition of the jackplate, loading, etc.. varies enough you can't really compare them by speed. Get yours propped correctly by reaching the 6K you state is the max rpm for that engine and the speed is going to be what it is.

[EuropeanAM]

If you would, please take a moment to review the Announcements at the top of the Forum, and update your post with the Required Info (serial number). Thanks!

While you are looking at the Announcements- note the "Performance Info" that's suggested. Please provide ACTUAL data from running YOUR boat (don't include your buddies' boat, or "speed calculations"... we need as precise a set of REAL world data as possible from your specific boat).

Also, has your dealer confirmed on the G3-2019 CDS that your engine is actually reaching 100% throttle position (WIDE OPEN THROTTLE)? I've found several with similar complaints that were NOT reaching WOT on the linkages at the throttle plate (though they were in the mid-90% range at WOT). It DOES make a difference!

Be glad to help- but that REAL WORLD data is absolutely critical. Nothing but the real-run facts gets the best chance of arriving at a favorable solution.

[wdr2064]

First of all yes Vexus did select the prop. My boat is at the dealer to get warranty issues addressed including speed so I do not have the serial number available at this time. I believe they are going to try different props on it. Max RPM I got it to is between 5800 and 5900. Top speed I got in the boat was touching 50 with just myself in the boat. The dealer has looked at the motor and they do not have a concern about the motor including RPM. Thanks very much!

[wdr2064]

If you would, please take a moment to review the Announcements at the top of the Forum, and update your post with the Required Info (serial number). Thanks!

While you are looking at the Announcements- note the "Performance Info" that's suggested. Please provide ACTUAL data from running YOUR boat (don't include your buddies' boat, or "speed calculations"... we need as precise a set of REAL world data as possible from your specific boat).

Also, has your dealer confirmed on the G3-2019 CDS that your engine is actually reaching 100% throttle position (WIDE OPEN THROTTLE)? I've found several with similar complaints that were NOT reaching WOT on the linkages at the throttle plate (though they were in the mid-90% range at WOT). It DOES make a difference!

Be glad to help- but that REAL WORLD data is absolutely critical. Nothing but the real-run facts gets the best chance of arriving at a favorable solution.

Ok, I did find the paperwork and the serial number of the motor is 2B701466. Dealer is satisfied that it is getting to wide open. In their on the lake test they did they said it goes to 5900 RPM. As I said earlier I got it to touch 50. I tried adjusting the jack plate height 1/4" at a time up to 1 1/2" higher than factory height it did not make a difference on speed. Motor runs really smooth, tons of torque on takeoff to plane. Smooth as silk just slow.

[EuropeanAM]

While I'm not familiar with this particular hull- I can tell you that we went through a number of struggles with customers running other "popular" 18-19' models with 150 Optimax models.

In the end- we found the best overall performance WITHOUT a jackplate. Several of the customers running jackplates actually picked up 4-5 MPH by removing the jackplate.

Not saying this "is" the case for you- but I can't overlook the fact that your buddy's boat has that one difference....

One other item- have someone hold the throttle open, and check the throttle plate itself to see if it is reaching the WOT position. I've had a couple that were off by quite a bit (I know... your dealer feels it is reaching WOT).

Note: Check that serial number. Engine/owner/boat info doesn't add up for some reason....

[Gsmith223]

While I'm not familiar with this particular hull- I can tell you that we went through a number of struggles with customers running other "popular" 18-19' models with 150 Optimax models.

In the end- we found the best overall performance WITHOUT a jackplate. Several of the customers running jackplates actually picked up 4-5 MPH by removing the jackplate.

Not saying this "is" the case for you- but I can't overlook the fact that your buddy's boat has that one difference....

One other item- have someone hold the throttle open, and check the throttle plate itself to see if it is reaching the WOT position. I've had a couple that were off by quite a bit (I know... your dealer feels it is reaching WOT).

Note: Check that serial number. Engine/owner/boat info doesn't add up for some reason....

Can you elaborate as to why this is? I am running a 4 stroke 150 non pro xs version and I have never had the speed I had with the 2 stroke. I have been told the same think but have never heard an explanation?

[EuropeanAM]

I suspect that it has a lot to do with the "moment of enertia" (in laymen's terms, the balance point between the weight of the engine and the weight of the hull, or point at which you might find the center of gravity). Keep in mind, that's a very "rough" explanation.

In short, I think that the 150 has a hard time lifting as much hull up and out of the water, while balancing on the pad. Moving the engine further AFT increases the amount of full that must be lifted (as the above mentioned point moves AFT when you set the engine back further).

Keeping the engine right on the transom moves that point back forward, and does, in some cases result in better performance.

This differs from the big-displacement, higher-torque and horsepower engines, which often "thrive" on more setback.

[Gsmith223]

I suspect that it has a lot to do with the "moment of enertia" (in laymen's terms, the balance point between the weight of the engine and the weight of the hull, or point at which you might find the center of gravity). Keep in mind, that's a very "rough" explanation.

In short, I think that the 150 has a hard time lifting as much hull up and out of the water, while balancing on the pad. Moving the engine further AFT increases the amount of full that must be lifted (as the above mentioned point moves AFT when you set the engine back further).

Keeping the engine right on the transom moves that point back forward, and does, in some cases result in better performance.

This differs from the big-displacement, higher-torque and horsepower engines, which often "thrive" on more setback.

Thank you this is exactly what I am experiencing. I am no longer get the boat up on pad like I was and the center of gravity feel like it has shifted. I thought it was because of the lack of positive trim while running and thought wedges would help. Now I am contemplating what else I can do, possibly go from a 6-4 inch jackplate would help.

[EuropeanAM]

That's got to be your call... but like I said, on the "other" brand we found going from a 6" to a 0" was the solution.

[berudd]

I suspect that it has a lot to do with the "moment of enertia" (in laymen's terms, the balance point between the weight of the engine and the weight of the hull, or point at which you might find the center of gravity). Keep in mind, that's a very "rough" explanation.

In short, I think that the 150 has a hard time lifting as much hull up and out of the water, while balancing on the pad. Moving the engine further AFT increases the amount of full that must be lifted (as the above mentioned point moves AFT when you set the engine back further).

Keeping the engine right on the transom moves that point back forward, and does, in some cases result in better performance.

This differs from the big-displacement, higher-torque and horsepower engines, which often "thrive" on more setback.

Hmmm, while running without the jackplate might result in higher top speed, I’m not sure this is the reason why. If the pad of the hull is a fulcrum, putting the engine farther back would put it on a longer lever and aid in lifting the front of the hull. The same can be said about the first of the engine. It’s farther back so when trimmed above neutral, the downward compnent of the force vector would have more of and effect due to being on a longer lever.

My guess was that it put the prop in more turbulent water. Usually, a jack plate is supposed to put it in better water but maybe that is not the case with this hull. If that’s the case, it’s disappointing the manufacturer of the boat didn’t discover this in testing.

It would be interesting to see pictures from the side of both boats running at top speed to see if one is running higher than the other. Also, did the OP post slip numbers from both boats? I think posted something to represent theoretical top speed but not sure if he posted any that actuals from each boat. If the slower boat is slipping more, that could be useful information.

[EuropeanAM]

Bruce- on larger, higher HP hulls, I would definitely agree that your premise holds true "most" of the time.

Time will tell on this hull... I only shared the above results as there are others that seem to prefer no jackplate (at all) in terms of performance (with a 150).

[wdr2064]

To me it still looks like when the math is done with the regular 150 four stroke with a higher gear ratio it will spin a prop faster than the Pro XS which means it will go faster all things being the same. Perhaps the Pro XS can handle a bigger prop and then go faster. The point is that both motors are sent to dealers with the same exact prop. Do the math and it seems to me that there is no physical way that the Pro XS can be as fast, in fact it has to be slower.

[TritonTRXV8]

Could the better performance without a jack plate on this hull be a cause from maybe being a little underpowered? These are almost 20 ft long boats with a 150 on them perhaps the additional setback is too much for the motor to get good lift? Idk just throwing it out there. Another 25 hp would go a long way.

[MichaelJ3]

To me it still looks like when the math is done with the regular 150 four stroke with a higher gear ratio it will spin a prop faster than the Pro XS which means it will go faster all things being the same. Perhaps the Pro XS can handle a bigger prop and then go faster. The point is that both motors are sent to dealers with the same exact prop. Do the math and it seems to me that there is no physical way that the Pro XS can be as fast, in fact it has to be slower.

Putting it all in the prop slip calculator on Merc Racing's site...
If you want the same speed, at same slip, and change only the RPM and Gear Ratios (6000/2.08:1 for the ProXS, 5800/1.92:1 for the regular), you need a 24p prop to get the same speed out of the Pro XS as you do on the Regular w/ a 23p.

Net, I'd consider trying a 24P prop, guessing the higher gear ratio of the XS will spin it, maybe even spin a 25p at acceptable hole shot.

[EuropeanAM]

Could the better performance without a jack plate on this hull be a cause from maybe being a little underpowered? These are almost 20 ft long boats with a 150 on them perhaps the additional setback is too much for the motor to get good lift? Idk just throwing it out there. Another 25 hp would go a long way.

That may very well be a contributor.

To the OP'er: I would not be inclinded to change prop pitch until you have real-world performance info on your setup, with your current prop.

[JoePA]

Could the better performance without a jack plate on this hull be a cause from maybe being a little underpowered? These are almost 20 ft long boats with a 150 on them perhaps the additional setback is too much for the motor to get good lift? Idk just throwing it out there. Another 25 hp would go a long way.

That boat isn't even close to being underpowered! A 150ProXS with a 23 Tempest on the 1980 is an excellent combo. The boat has almost instant holeshot and high 50's for speed, these numbers are no plate and has excellent bow lift. These are the numbers I have experienced while running the Vexus.

[TritonTRXV8]

That boat isn't even close to being underpowered! A 150ProXS with a 23 Tempest on the 1980 is an excellent combo. The boat has almost instant holeshot and high 50's for speed, these numbers are no plate and has excellent bow lift. These are the numbers I have experienced while running the Vexus.

Exactly no plate. Which was stated earlier seemed to improve performance. Op is having speed issues and has a jack plate which is why i stated that with the jack plate it may not get the lift it needs to perform correctly. If a motor cant get lift with too much setback its generally from not enough hp to carry it. Simple speculation is all. Underpowered is up for opionion im not getting into that.

[wdr2064]

Putting it all in the prop slip calculator on Merc Racing's site...
If you want the same speed, at same slip, and change only the RPM and Gear Ratios (6000/2.08:1 for the ProXS, 5800/1.92:1 for the regular), you need a 24p prop to get the same speed out of the Pro XS as you do on the Regular w/ a 23p.

Net, I'd consider trying a 24P prop, guessing the higher gear ratio of the XS will spin it, maybe even spin a 25p at acceptable hole shot.

Your math came out pretty much exactly the same as mine...

[EuropeanAM]

The "catch" is that the math is based on theoretical numbers.

I still think the solution is to remove the jackplate and then setup/prop based on how the 23P performs WITHOUT the jackplate.

[wdr2064]

OK I Called technical support for mercury motors and the technical person told me that if you have the regular four stroke 150
And the pro xs 150 And Send them out on the same hall with the same prop the regular four stroke
Will absolutely be faster than the pro xs Because of the gear ratio