Missing some speed and 300 RPM Off

[go boater]

Hello to all -
I'm in the throws of getting the boat squared away for the season and she's turning up only 2200 rpm's on each motor WOT with a clean bottom, 1/3 Fuel, NO Personal Belongings...

Anyone tell me how much pitch I can take out of the wheels to boost her up by 300 rpm to the rated WOT (2500 on 6-71's). It's a 45 viking that is only cruising at 20 kts and topping out at 23-24 (I definitely feel that I'm missing some speed)

Thanks to all for your feedback - just not sure if / how I can find a reliable calculator online to help. Right now, I'm thinking conservatively @ 1" of pitch being taken out...

[RCARNEY]

Did you ever have all your turns? If you have lost them since last season, I would not start with a trip to the prop shop.

[go boater]

Did you ever have all your turns? If you have lost them since last season, I would not start with a trip to the prop shop.

NO, that is a great question though. The boat is actually new to me, and the previous owner always got 2200 RPM's and one motor is actually fresh and runs the same as the older motor.

[jawz12]

one inch in pitch isn't gonna do it for ya...every inch in pitch usually yields 150 rpm...
it may be a wise move for you to consult a prop shop...i use and reccomend pat whelen,eastern prop,pat has a hale mri machine,his work is perfect,computer readouts before and after...pat's number is 609-390-0448

[Capt. Stu]

Bear in mind that you'll lose cruise speed taking pitch out of the wheels. If the boat only hit 22-2300 at WOT for the prior owner, the 6-71's were being overloaded (& their life shortened). 2 things I might suggest before taking out pitch & slowing the boat below 20 knots would be having the shafts "photo-tached" to insure the gauges are accurate & if they are replace both the primary & secondary fuel filters & see if your can squeeze more fuel to the engines to get redline. If you can't get to redline after this & there are no other problems with the engines, a trip to the prop shop is warranted.

Stuart

[Wild Life Management]

I know you said you have a clean bottom, but have you had it hauled and cleaned recently or does the paint just look clean? Just wondering how clean your shafts and props are? If I have a moderate amount of growth on my running gear my 671's will turn around 2200 RPM WOT, but they turn 2500 RPM WOT with clean gear.

[go boater]

I know you said you have a clean bottom, but have you had it hauled and cleaned recently or does the paint just look clean? Just wondering how clean your shafts and props are? If I have a moderate amount of growth on my running gear my 671's will turn around 2200 RPM WOT, but they turn 2500 RPM WOT with clean gear.

Yep, she's all clean underneath. After doing some research on boatdiesel website calculator, I might have the wrong wheels on the boat. Many report a 23-24 knot cruise and 27.5 to the pins WOT...

Would LOVE to get that speed out of her with the right RPM's!

[jawz12]

Yep, she's all clean underneath. After doing some research on boatdiesel website calculator, I might have the wrong wheels on the boat. Many report a 23-24 knot cruise and 27.5 to the pins WOT...

Would LOVE to get that speed out of her with the right RPM's!

that's usually the case,most boats have way too much prop on them...

[atlantis]

Capt. Stu is dead on. The props should be your final adjustment to dial in performance. If motors,tachs,throttle linkage,filters,bottom condition,etc. all check out, we would be glad to adjust your wheels for you.

The number of r's you will gain per inch of pitch removed will depend on your boats gear ratio.

If you would like your props checked- we can measure them in on the Prop Scan computer in 10 minutes while you wait.
( Cost is Free.) We also lend out prop pullers for free if you need them. Pictures of our shop, the Prop Scan computer and our work can be seen on www.atlantispropeller.com

Ray / Atlantis

[atlantis]

Also, decreasing pitch does not always result in a loss of speed. Sometimes the engine is being held back from developing its maximum horsepower / correct torque curve.

In some cases we have seen speed increases of 2-3 knots when decreasing pitch- (allowing the motor to develop its hp / torque).

Hope this helps,
Ray 856.231.0106