Prop selection for Q25 w/300 Verado

Mscott

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Just curious what anyone who has a Q25 with ESP package is running for a prop on a 300 Verado? Dealer set mine up with a 17 pitch and I am only getting 46mph at 6200 rpm's. The boat comes out of the hole very fast and gets on plan with full fuel and 6 adults.
 

joecfd1

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That doesn't sound out of line for top speed. What hole is the drive rigged in? Is it an Enertia prop? We have a Q25 Swingback with a Verado 350 with a 17 pitch Enertia prop and we're seeing 51-52 mph. What were you hoping to see???
 

Mscott

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That doesn't sound out of line for top speed. What hole is the drive rigged in? Is it an Enertia prop? We have a Q25 Swingback with a Verado 350 with a 17 pitch Enertia prop and we're seeing 51-52 mph. What were you hoping to see???
It is last in the top hole, engine is as low as it can go. It's not an Inertia Prop. I was hoping to see 50mph and have a little better cruise speed.
 

Vikingstaff

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It is last in the top hole, engine is as low as it can go. It's not an Inertia Prop. I was hoping to see 50mph and have a little better cruise speed.
PROP: The Enertia props are fantastic on the Mercury Verado’s. For that motor, that would be by far my #1 prop recommendation. What’s on it now for a prop?

HOLE MOUNT: Based on what you said, my guess is your are mounted too low. When fully underway, is your cavitation plate basically level with the water, OR is it fully submerged. IF fully submerged, you are mounted too low, and your lower unit is too deep. That is creating drag which is a) slowing you down, and b) not good on that lower unit.

RPM/PROP PITCH: The RPM range for your motor at WOT is 5800-6400 RPM at WOT. Ideally you want to be towards the very top of that range with a LIGHT load. You were at 6200 with a moderate to heavy load. Spitballing here, I think you could go up 1 for sure, maybe 2.

If you really want to dial it in, I’d change the engine hole mount first (IF the cavitation plate is submerged). Track RPM at WOT light load, and heavy load. I’d then switch to at least a 17p Enertia Prop. Track RPM at WOT the same way as above. Depending on results, then try out both an 18 and 19 pitch Enertia and compare to RPM/load numbers.

When done, you should be totally dialed in. You have a lot of boat you are pushing with that motor, so that certainly is going to impact things. However, I think you could get to that 50 mph mark by dialing in the items above.
 

RodEarl74

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Sounds about right to me with it rigged in that top hole. I recently switched mine from the top hole to the middle hole. While it was in that top hole running a 17p enertia prop we were able to see 50.6MPH on the GPS. Load was light, 3 adults, half tank of fuel and both Biminis deployed. Water conditions were perfect

I haven't really been able to test what it would do with a light load at WOT. First time we went out after re rigging we had a boat full of people. I really didnt notice any difference in fuel economy, cruising speed or whole shot. What I was able to notice was that the cavitation plate now sits at the proper height while on plane. It does tend to porpoise if I trim it past about 5 degrees.

Looking forward to my next trip to see what the results are.
 

Michiman

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Mscott, what is your prop diameter?
 

joecfd1

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Alicedream

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I think 46 MPH with a 300 HP motor on a Q 25 is right where it should be. I have a 300 HP on a R23 and I get 45 to 47 and an occasional 48. Your boat is bigger and heavier.
 

Mich QSBA

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I've got an 2019 25 QSBA (arch boat) 300 verado V8. The RPM on this motor is 5200-6000 WOT. I'm running the 17p enertia, with myself, GF, & 100lb. Lab, 20 gallons fuel, 2-4 hours on engine, short bursts 44.5 MPH. now with 9.5 hrs same conditions its picked up to 46.5. These boats with an arch are HEAVY. Hope these helps!
 

Michiman

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14.5 is the diameter.
From what I've read on the subject, I think your diameter is on the small side for such a large vessel. I'm turning a 15.5X13 on a GCW 2574 with a 250 Verado with a top speed of 40 MPH decently loaded. Do you seem to have any ventilation and/or cavitation issues? Generally speaking, I'd agree with the folks above that you're about where you should be speed wise.
 

Dahbull

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Hello,

I have a Q25 fast back with arch and Yamaha 300. A 16” pitch prop. Motor is mounted as low as it can go. The best I can do with a half tank of gas and two people is 43 MPH.

I’m questioning if the motor is mounted too low. With the motor trimmed for best speed/RPM the boat throws water (think rooster tail) twice as far as either outboard toon. The ventilation plate is most definitely submerged but not sure how far. At least an inch if not more.

Dealer said they would move the mount but at my expense. I just purchased the boat middle of last summer and haven’t had much time with the boat to really get things tuned in.

Thoughts on
1) Motor mounting height?
2) Dealer paying for cost to get it right?
3) Prop selection for motor?

Thank you
Dave
 

Vikingstaff

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Hello,

I have a Q25 fast back with arch and Yamaha 300. A 16” pitch prop. Motor is mounted as low as it can go. The best I can do with a half tank of gas and two people is 43 MPH.

I’m questioning if the motor is mounted too low. With the motor trimmed for best speed/RPM the boat throws water (think rooster tail) twice as far as either outboard toon. The ventilation plate is most definitely submerged but not sure how far. At least an inch if not more.

Dealer said they would move the mount but at my expense. I just purchased the boat middle of last summer and haven’t had much time with the boat to really get things tuned in.

Thoughts on
1) Motor mounting height?
2) Dealer paying for cost to get it right?
3) Prop selection for motor?

Thank you
Dave
1) Certainly sounds like it needs to be raised up a little bit more.

2) If they are the one’s that mounted it too low originally, I wouldn’t be happy with them wanting me to pay for it. However, if you got it last summer, and just brought it up as a concern this summer, I can also see where they would say its on you. However, you bought a flipping Q-series from them!!! That’s about as big ticket as it gets. Seems they could take care of such a straight forward job to keep a Q-series purchaser happy.

3) I wouldn’t do anything prop related UNTIL the motor is raised up in the water. Then track RPM’s and Speed at WOT, sharing that info along with MAKE/MODEL/Dia/Pitch prop, and boating conditions (#people, gas, windy, calm, etc.) when you got your performance numbers. Plenty of people can then pipe in with advice. You very well might hear before that from Q owners with that motor that can share what prop is working great for them currently.

Finally, there is a performance thread tucked away in these forums. Do a search for it in the upper right search box. You very well may come across a few people with your set up sharing what prop they are dialed in with on their boat. That might speed up the prop search for you.

That said, you have a very heavy boat. So overall, your speed is nothing to sneeze at.

Good Luck!
 

RodEarl74

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Well, took the boat out yesterday for a fun day on the water and a speed test with the motor mounted in the 3rd hole.

Here is what I found.

Just the wife and I, half a tank of fuel and both Bimini's deployed.

50.1MPH at 6200RPM's trimmed 5.4 degrees. Water conditions were perfect, very little wind.

I think I can get 2 or 3MPH more if I put the top down!
 

Dahbull

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Rodearl74,

What size prop (diameter and pitch)?
Motor?
Boat model and length?
Do you have an arch?

Thanks
 

RodEarl74

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Rodearl74,

What size prop (diameter and pitch)?
Motor?
Boat model and length?
Do you have an arch?

Thanks
2018 Bennington Q25SB. No arch. Verado 350 turning the Enertia 14.5x 17p prop.
 

Dahbull

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If possible, could any of you getting good performance from your Q25 look at something?

Currently, the ventilation plate of my Yamahas 300 is level with the bottom of the center toon. I looked at the dealership at a couple of mercury 400 motors mounted on Q’s. I noticed that those ventilation plates are between .5 and 1.5 inches above the bottom of the center toon.

Bennington’s recommended mounting location is top hole for both Yamaha and Mercury but the shaft length of the two motors is different causing the location of the ventilation plate to be different.

What I’m trying to figure out is exactly how far above the bottom of the toon does the mercury ventilation plate sit? I am wanting to know how far up I should move my motor to get the correct height of the ventilation plate.

Thanks all.
 

Folsom Dan

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What I’m trying to figure out is exactly how far above the bottom of the toon does the mercury ventilation plate sit? I am wanting to know how far up I should move my motor to get the correct height of the ventilation plate.
Take a look at this . . . https://www.boats.com/how-to/the-outboard-expert-boost-speed-with-outboard-engine-height-adjustments/

General rule of thumb should be that the ventilation plate sits at water level when underway and trimmed. According to the linked article - that general rule can be modified for different applications.
 

Dahbull

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Take a look at this . . . https://www.boats.com/how-to/the-outboard-expert-boost-speed-with-outboard-engine-height-adjustments/

General rule of thumb should be that the ventilation plate sits at water level when underway and trimmed. According to the linked article - that general rule can be modified for different applications.

Thanks. Very good article. What I gather thus far is I need to measure distance from transom to prop. For every 8-10” I can raise my motor 1”.

What I don’t know is everyone on this site seems to have a mercury engine and nobody with a Yamaha engine is responding with data. What say you Q25 owners with a Yamaha outdrive?

Thanks
 
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