RPM question

[Freespool]

Hello all,
I recently purchased a 2530 Parker with twin 150 Yamahas. I put on a stainless tower, added two 6 volt batteries to the system, an inverter, as well as a large bait tank. I am still in the process of dialing it in. As I run the boat I am only getting 5000 RPM's wot. At this speed I am burning 16.5 - 17 gallons per hour. I am wondering if I need to reprop or if this what I can expect with all of the additional weight I have added. The Yamaha spec sheet for my rig says I should be burning around 13 GPh. Your thoughts are appreciated.

 

[DaleH]

You need to know the maximum RPMs of those specific motors, which could be 5,500 or 6,000 RPMs. Then you should turn ideally no less than 200 RPMs off that number @ WOT.

Sounds like both have too steep a prop pitch ...

 

[warthog5]

Sounds like both have too steep a prop pitch ..

Yep...Need to go down in your pitch number.

 

[Megabyte]

Also check the mounting depth.
The motors might be too deep.

 

[Freespool]

Thanks all,
Where do I find information regarding how many RPM's I should turn? The only information I can find is on the Yamaha website where they have listed the numbers from a test run on a 2530 Parker. I assumed the max RPM's were 6000 for all 150's. Is this not accurate?
Also, does it seem like I am burning a lot of fuel?

Lastly, the engines are mounted as low as they can go....

 

[DaleH]

Lastly, the engines are mounted as low as they can go....

That's but one problem ... they should be mounted as high as they can to give excellent all-around performance with the prop it wears, which could be +/- 1-hole difference for different props.

Confirm the maximum RPMs with your Dealer, for that motor and year ... in writing. DO NOT tell them you're only turning 5K ... as they may say 'that's OK". Well, it isn't. Most Dealers simply don't have the time to custom tune the OB and prop combination to the hull.

Edit: By a quick search, if those are the newer 4-stroke 150s (F150TXR model) they appear to be 6,000 max RPMs motors. On that boat, I myself wouldn't accept turning less than 5800 in cool temps, on a clean bottom, with all std gear carried, and half to 1/3rd fuel.

Note, all normally aspirated motors will lose a few hundred RPMs on hot, hot days ... so keep that in mind too.

 

[Freespool]

I mis-spoke. The motors are as high as they will go. The year is 2006, and I too am under the impression that they should turn 6000. I have spoken to a prop guy but he was not much help.......

 

[Brent]

Which mounting hole?
The top one is 1 and bottom one on the mount is four

 

[Brent]

Or hole is farest from water and bottom hole is closer to the water

 

[Freespool]

The motors are mounted low. In other words, they are mounted so the prop is deep in the water. I cannot raise them as they cavitate with certain sea conditions.....

 

[DaleH]

You need your existing props re-pitched or replaced. If in New England, contact New England Propellers in Plymouth, Mass, as they can re-pitch your props. If looking to upgrade (cha-ching due to the 2 motors) contact Ken at www.propgods.com .

You are KILLING your motors running them like they are ... you need to raise your RPMs big time!