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Quick question maybe you guys can help with

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Voltone

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I just bought a 2018 SX24 Tritoon with a Yamaha 150 Four Stroke. It’s sucking the gas more than we feel it should (we are starting to record this now to get more accurate usage) and the top speed with nothing on the boat but me as the driver is 32 MPH recorded by GPS. We now have 36 hours on it. Does this sound about normal?? A friend of ours has the 2017 SX25 with the same toons and same floor plan and he isn’t using near the gas we are and can run 40/41 MPH WOT. Prop is exactly the same. Obviously his boat is larger as well. Dealer isn’t being much help. Should I have someone else look at the motor??
 
Welcome Voltone! I can't give first hand knowledge but based upon what I've read on this forum, most folks running a 150 tri-toon are hitting around 40 MPH on a 21 or 22 model, not a 24. I've got a 25 with a 250 HP that tops out at 40 MPH (although a bit heavier than you for sure). I'd have to say I'm a bit skeptical of your buddies performance numbers but if they are accurate, he's certainly dialed in with outstanding performance in my opinion. What is your WOT RPM?

Oh, and post some pictures so we can drool over your new baby!
 
Very odd since you're both using the same prop. Do you both have the same RPM at WOT? Are you adjusting the trim? Getting the nose up can make a big difference.

Just curious -- what prop (name and size) are you using?
 
I would also ask what is your top rpm ?
The Yamaha 150 will burn 16-16.5 GPH at 6,000 rpm. Unless you have a fuel flow meter or the Yamaha Command Link instruments you will not be able to see actual fuel burn as it happens and anything else is just a guess. All large motor use a lot of fuel if you run them in the upper ranges...There is no secret as fuel burned is directly proportioned to the hp used.
Another poster on Power and Props 2014 scwx with Yamaha 150 is also disappointed with his top speed but he can not get close to 6,000 and only 33 for a top speed...
Can you provide any more info?
 
So played around with it last night. WOT was 4800 RPM and 32.4 MPH. I’ll have to get the name and info off the prop.
 
Way too low for WOT!
 
Voltone said:
So would that be prop issue or what??
Click to expand...

Probably is a prop issue. I’d at least rule that out first. Can you post your specific make, diameter, and pitch prop? Lots of people on here run Yamaha 150’s, so you should be able to get some GREAT feedback from them once they know what you are using.

My guess is your are WAY over propped, need to bring it down in size to get your RPM’s up at WOT, and in conjunction with that, your MPH should increase too.
 
Would also be interested what prop as you are not doing the engine any good lugging it like that and you are losing a lot of top end. In the Yamaha Performance Bulletins I have with the Bennington's about your size the 150 Yamaha they are running a 14.5x15 # 68F45970-10-00 prop and turning between 5850-6000 rpm. This is the stock Yamaha prop that came with the two engines in the test I have on two different Bennington boats. With your boat making 4800 rpm you are only making about 105 HP. Most 115 hp engines correctly propped running at 6000 will go as fast as you are going.
Again, if the engine is running fine then you definitely have a prop issue.....On a correct reving Yamaha 150 it will gain about 8 mph between 4800-6000 if propped correctly and running well....
 
Another thing to check if your speed is down and fuel consumption is high is water in your pontoons. It does happen occasionally.
Your speed is definitely low for that set up. I have a 2018 ssbxp SPS with a 150hp Merc. and I’m at 35-36mph (5200rpm @ wot) and I have Sea Legs on mine which drops your speed by 4-5mph.
 
Renegade34 - So your WOT is about 5200 RPM’s?? I’ve played around with it and gotten mine just over 5100 with just me on the the vessel but still 32 MPH
 
Your RPM's are too low! You need less pitch.
 
I agree unless he is heavy due to water in hulls, very dirty tubes or he has a fuel restriction.
A lower pitch prop will tell a lot as it will not rev much higher if he has a fuel restriction and you can start to rule out other issues but the prop is the first thing I would start with as well as the easiest.
 
Voltone said:
Renegade34 - So your WOT is about 5200 RPM’s?? I’ve played around with it and gotten mine just over 5100 with just me on the the vessel but still 32 MPH
Click to expand...

Yep 5200rpm @ wot. I may try a 16p to get rpm up a bit but not sure. I’m fairly happy with the performance as is. If I’m only going to gain 1-2 mph I’ll likely leave it alone but if I can gain over 2 mph it would be worth it.
 
Here’s all I got WOT - just pulled it out of the water and taking to dealer to look at
 

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How about motor height, I changed mine several times to get max speed.
 
I have both 3 blade and 4 blade. The 4 blade WOT is around 5200, 3 blade 6k+ @ ~39mph. You should update your signature with your setup. It's easier for people to look at what you have and maybe help with suggestions.
 
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