Very disappointed in performance of F115

[Av8erdunn]

I have a 2006 Yamaha F115 on back of a 2006 Polar 1900 center console boat and need feed back. I know its on the smaller side for an engine on this boat thats rated for a 150 but I still feel performance should be better than it is currently. I just replaced all the filters including the VST and had injectors cleaned by MR Injector and the motor runs flawlessly other than sometimes after cruising when I return to an idle the idle speed will drop to 600 and run rough but it eventually comes back to 800 where it should be.

Thats not my problem. My boat weighs around 2000lbs and is 19' long. I am running a 13x17ss prop at 5700 RPM and I am only seeing 32mph top speed trimmed on a calm day no wind and only me in the boat. I bought the boat over the winter and just got it in the water after fixing the clogged VST filter this weekend. Reading reviews, people say similar boats are getting close to 40 with this same engine . I thought it would at least see 35-36 mph. Am i being unrealistic?

Whats your thoughts?

[boscoe99]

My thoughts are that the boat is seriously under powered for your needs. I don't see the motor as being down on power. But you can find a dealer who has a test wheel to verify that the motor is making rating power, or not.

Here is a link to a Yamaha performance bulletin that has an F115 installed on a 19' center console. Maximum speed obtained was 39 MPH and this was on a cool day (air temperature of 61 degrees F).

http://yamahaoutboards.com/sites/def...111115_OCC.pdf

Note that the PB boat was brand new. A new boat is as light and as fast as it will ever be. Start equipping the boat as it will be used and the weight goes up and the WOT speed will go down.

Now what you can do is to inspect the motor to see if it is optimally mounted on the boat. Most are mounted lower than optimum. A few more MPH and RPM's can generally be had at WOT by raising the motor a bolt hole or two. Then you can start throwing 500 dollar propellers on the motor to see if another MPH or two can be obtaining with a different propeller.

[Av8erdunn]

Yeah, I feel certain that its making power. When I was running yesterday it was about the same temp outside as the test boat. I realize its a small motor for this size boat but I have a friend with a 17' cape horn and an 88 Johnson that runs about 34-35 mph WOT. The cavitation plate should be about level with the bottom of the boat shouldnt it? I think my RPM's are where they should be as well, its just very disappointing to read reviews of other boats running faster with smaller motors. I guess I will just live with it for now. Do I need to cruise any faster than 26-27mph at 5000RPM? No but it sure would be nice to cruise at that speed at 4500RPM!!!

[boscoe99]

The anti-ventilation plate can be several inches above the bottom of the boat. Depends to a great extent on the boat bottom and the propeller being used.

With the boat at cruise speed or WOT speed, with the motor trimmed up just to the point of maximum efficiency, have someone drive while you lean over the back of the boat to inspect the motor. You should be able to see the anti-ventilation plate skimming the surface of the water. Something like the photo below:

[99yam40]

the PB shows a 13 1/4 X 17 aluminum prop being used and you are using a 13 X17 SS.
SS props usually have more cup to them, but might be smaller diameter. and we have no idea if you prop is as good as it should be.

Just because you feel certan the motor is making the proper HP does not mean it is .
need to make sure.

Have you weighed your rig to make sure it weighs what it should ?

[scofflaw]

And if the motor is mounted at the correct height and it's still a slug, sell the 115 and put the 150 on it needs. I hate being under powered, downright embarrassing. That's why I have a 225 2 stroke on my 20' CC...YEE HAH

[Av8erdunn]

Just curious but if it wasn't making correct power, I wouldn't be able to achieve the correct operating RPM. Right?

I haven't weighed the boat to be sure of the weight.

I am hoping to run it tomorrow afternoon to see what the ride height is.

[boscoe99]

Just curious but if it wasn't making correct power, I wouldn't be able to achieve the correct operating RPM. Right?

I haven't weighed the boat to be sure of the weight.

I am hoping to run it tomorrow afternoon to see what the ride height is.

If and when you do, I suspect that you will be surprised. I sure as heckfire was with my boat. It was about a thousand pounds more than I had thought.

[pstephens46]

If and when you do, I suspect that you will be surprised. I sure as heckfire was with my boat. It was about a thousand pounds more than I had thought.

1000 pounds more? What kind of boat? What was the additional weight? Water?

[boscoe99]

1000 pounds more? What kind of boat? What was the additional weight? Water?

It was a 21.5' walk around cabin.

It was not water. It was all "stuff".

Drive by a weight scale and see for yourself what your own boat weighs. I suspect that it will never be lighter than what is forecast.

[pstephens46]

It was a 21.5' walk around cabin.

It was not water. It was all "stuff".

Drive by a weight scale and see for yourself what your own boat weighs. I suspect that it will never be lighter than what is forecast.

Sounds like your wife loaded the boat. My wife tried to bring a fruit tray on mine. Not to mention 14 chairs, hundreds of towels, etc.

[DennisG01]

I'm assuming it's not (likely a trailered boat), but... is the hull bottom dirty?

Is the prop in good shape? Definitely check the AV plate height while at speed.

Hopefully this is not your issue... Polar was kinda known for having lot's and lot's of stress cracks from improper screwing, before going out of business. Is yours plagued by that? If so, those cracks could have opened up enough to allow water in. It would take an awful lot of large cracks to make enough of a difference, weight-wise, but the suggestion of going to a CAT scale would at least eliminate a variable. Your trailer info plate (and possibly the title) will give you the trailer's "unladen" weight so you can subtract that from the total.

[boscoe99]

Sounds like your wife loaded the boat. My wife tried to bring a fruit tray on mine. Not to mention 14 chairs, hundreds of towels, etc.

And the house. Sh1t everywhere.

I like my countertops with nothing on them. She likes doodads everywhere. And then wants me to dust around all one million of them.

Towels you say? Can any one person possibly need more than one, possibly two? Why is our bathroom closest full of the damn things?

If women were not women then no man would want to have anything to do with them.

[Av8erdunn]

I'm assuming it's not (likely a trailered boat), but... is the hull bottom dirty?

Is the prop in good shape? Definitely check the AV plate height while at speed.

Hopefully this is not your issue... Polar was kinda known for having lot's and lot's of stress cracks from improper screwing, before going out of business. Is yours plagued by that? If so, those cracks could have opened up enough to allow water in. It would take an awful lot of large cracks to make enough of a difference, weight-wise, but the suggestion of going to a CAT scale would at least eliminate a variable. Your trailer info plate (and possibly the title) will give you the trailer's "unladen" weight so you can subtract that from the total.

Yeah, she is clean! Even has a fresh coat of wax. The hull is actually in really good shape. I had read about there issues before buying it and wouldn't have pulled the trigger if it had stress cracks any where. I am going to Check ventilation plate height and then try to weigh it to see what I come up with. Also going to have my prop looked at by a local prop shop.

[pstephens46]

And the house. Sh1t everywhere.

I like my countertops with nothing on them. She likes doodads everywhere. And then wants me to dust around all one million of them.

Towels you say? Can any one person possibly need more than one, possibly two? Why is our bathroom closest full of the damn things?

If women were not women then no man would want to have anything to do with them.

That's the most charitable version I have ever read.

Now how about the Tupperware? How many of those damn things do you need? Enough to fill 5 fridges? Open the cabinet and they fall right out. No matter which one you grab, no lid can be found. They can find in seconds. With derogatory comments....don't get me started on coffee mugs and Tervis tumblers.

No thread hijack here. Just mental masturbation until OP reports back.