Prop Issues

[Shaker1234]

I recently purchased a brand new F150 and am having difficulties getting the boat up on plane. I have an 18ft Whaler so ample power for the boat. It really struggles and takes a long time. If I have four or more people it is really challenging. It if give it too much throttle then the prop slips.

Yet my WOT is 6,000 - 6200 rpm at boat speed is around 34knots. Normal cruising speed is 5200 rpm at around 24 knots. Anything under 5,000 rpm and the boat falls off plane depending on the number of people on board.

I have an aluminum alloy prop right now so thinking about going stainless.

Any thoughts?

[Jason2tpa]

18' Whaler w/150HP should be jumping on plane incredibly fast, assuming a normal weight load. And sounds like you're topping out the spec rpm range too. I pulled a performance bulletin for a somewhat similar hull, which produces 51MPH at top end rpm. 34 knots = approx 40 mph, so you're definitely losing mph...but where? New engine so let's rule out engine issue. Next...engine height. The ventilation plate should be between 1/2" to 3/4" above or below the transom bottom. If mounted too low, you're increasing drag. If too high, increases probability of prop slip and hull performance issues. Apologies if this is a no brainer for you....are you using the tilt/trim when underway?

https://yamahaoutboards.com/en-us/ho..._8-19-2019-bay

[99yam40]

hull water logged?
boat weighs a lot more than it should

What prop are you running?
who rigged the new motor on the boat?

[Shaker1234]

18' Whaler w/150HP should be jumping on plane incredibly fast, assuming a normal weight load. And sounds like you're topping out the spec rpm range too. I pulled a performance bulletin for a somewhat similar hull, which produces 51MPH at top end rpm. 34 knots = approx 40 mph, so you're definitely losing mph...but where? New engine so let's rule out engine issue. Next...engine height. The ventilation plate should be between 1/2" to 3/4" above or below the transom bottom. If mounted too low, you're increasing drag. If too high, increases probability of prop slip and hull performance issues. Apologies if this is a no brainer for you....are you using the tilt/trim when underway?

https://yamahaoutboards.com/en-us/ho..._8-19-2019-bay

My boat is the Ventura so might be a little heavier but I get no where near those performance results. I used a local company to mount the engine so I am assuming it was done correctly. When I trim the engine I get about 10% more speed.

[Shaker1234]

hull water logged?
boat weighs a lot more than it should

What prop are you running?
who rigged the new motor on the boat?

Yes someone else suggested water logged but when you look at the boat resting in the water it appears to be the right height.

[99yam40]

you did not answer my other questions

[Shaker1234]

you did not answer my other questions

Aluminum 14-1/4X17 3B RH PROP

A local marine services company installed it for me.

[99yam40]

Aluminum 14-1/4X17 3B RH PROP

A local marine services company installed it for me.

did they pick the prop for your boat?
did you ask /tell them about it not functioning properly since they rigged it?

is that prop shown on performance bullions for a boat like yours with that motor?

[Shaker1234]

did they pick the prop for your boat?
did you ask /tell them about it not functioning properly since they rigged it?

is that prop shown on performance bullions for a boat like yours with that motor?

I have talked to them and the only thing they can think of is the boat might be waterlogged.

Where do I find performance bullions?

[99yam40]

weighing the boat on a trailer would tell if it was close to the factory spec.
Yamaha or boat manufacture might have info.
web search would give info I am sure