The Boating Forum - 200 Yamaha OX66 Performance

I just purchased a Sea Hunt 215 with the 2 stroke Yamaha 0X66. On my first time out I was only able to get up to 34 knots WOT. While this is fast enough, I know of others with 150hp Yamahas getting better performance. I played with the trim and got it to this max speed.

The boat has bottom paint, not sure how much that will cut performance, would think too much. Also had about 60 gallons of fuel and my family of 5 onboard.

Is this reasonable to expect. Honetly expected high 30s / low 40s at WOT.

Need to know the RPM. You have the wrong prop. I have the 232 with the same motor at WOT I am at 5300 @42MPH

Running about 5500 RPMs. I was wonder if it may be the prop. If that's all I'm probably OK, it does have a good hole shot and the kids still enjoy skiing and tubing. Guess I can give up some top end for them.

Where did you get the speed reading?* From your GPS or from the speedo?* Also, was it 34 knots or 34 mph?

34 knots is about 39 mph.* With a new motor, a full tank of gas and bottom paint that sounds pretty close.

If you have the Yamaha digital speedo and its reading knots, its a simple change of the dip switches on the back to make it read MPH.* Do a search on the Forum...I know SIM has posted the directions on how to do this.

Parthery,
Reading from GPS and it is knots. Speedometer on boat works when it decides it wants to, can't rely on it.

Reason for the post, I know someone with the same boat, 50hp less and is running just above 40 knots.

I'm thinking it's probably prop related...................just not sure.

I have that motor on an Aquasport 215 Osprey Sport. My top speed with 100 gallons of fuel and 3 -4 people aboard is 42MFG (by GPS) if optimally trimmed and little or no resistance from wind & seas.

You may be overpropped...my 208 with a 200 ox66 runs 45 MPH by the GPS at 5500 rpm...the Yamaha speedo is off by about 1 MPH.

I am turning a 13.25 x 17 Yamaha SS prop....

There is a 15.25 x 17 SWS prop for sale in the Trading Dock :)

Thanks for the input, I think it has come down to the prop.

I just talked with the prop manufacturer and said he thinks the dealer probably pulled the prop from another boat. The current prop is a 13.75 X 19 and he suggested I go with a 14.75-15.25 X 17 4 blade prop.

Any thoughts on this. Thanks again for the input.

I'm no prop expert, but IMO you don't need a four blade on that rig. What's the dealer's rationale?

Eric,
I wondered too, but this is not the dealer it's the prop company. He said it would give more hole shot, plus should plane out about 4-5 knots quicker.

I believe I'm still going with a 3 blade.

I've talked with a couple dealers today and I believe I'm more confused now. One even recommeded a 21 pitch with lesser diameter.

I have a friend who's let me borrow at 14.75 X 17, steel 3 blade. I'm going to try it this weekend.

At 5500 rpm that motor is running at the top of its recommended rpm range for WOT. However, to get only 34 knots out of that boat/motor/prop with the motor running at 5500 rpm suggests some other factor is at work here. Theoretically, a 19 pitch prop running at 5500 rpm should give you about 46-47 mph. Theoretically, at 34kts you're getting, that's 26% slip which is abnormally high. Something else is happening here...

How old are your kids? Are they young adults or small children? Were they sitting in the front of the boat? How much wind? Was your speed trial on a river -- in other words, was there a current in the body of water? If you're going against a river current, the GPS speed will reflect the fact that the medium on which you're moving is moving also. For example, if you were going against a 3kt current, the boat was actually doing 37 knots through the water (which would put it in the ballpark for where it should be at WOT). If you were going with the current and the GPS showed 34 knots, you were actually only moving 31 knots throught the water (and thus you would have some other unidentified problem).

Don't run out and buy a new prop yet, you may be seeing exactly the performance that you should expect given the circumstances.

WOT range for that engine is 4500 to 5500, max HP is developed at 5000. So if you keep it above 5000 with a standard load you should be fine. Larger diameter will reduce your rpms to a small extent and provide less slip. I don't think a 15.25 is the right diameter. Either the standard ss black 14.75 or the standard SS black 15 inch may do the trick. The 15.25 is a SWS prop which is a very aggresive prop more for the larger V6's. It has more cup and rake than the standard black. Since it is so aggressive you would have to reduce pitch. If you were to go to a 4 blade you have to reduce your pitch to keep the same rpm. since there is more drag in the water.
So trying a 14.75 x19 or a 15x19 black ss wheel is something you may want to try. This should reduce you slip.
If you were to step up your 13.75 to a 21 you would probably take your rpms down to around 5100+ or - 100rpm. You may gain more top speed,but planning the boat may suffer.
Running your friends 14.75 x17 will probabaly net you a few more rpms, which will take you over the 5500 max, since your are at 5500 with a 13.75x19. In my estimation you may gain up to about 300 rpm.

Hi rdsrb5 , just got your email and replied. (we have the same boat, I'm running the F150). My prop is the 17inch x 13 3/4 standard black Stainless (now with dings) and while I'm running will full gas I usually only have 2 or 3 people. I've found the wind conditions and bimini up can make an amazing difference to top end. I'm still getting over 40mph trimmed out, but think I'm trimming to far to get to 5800 rpm (steering gets too scary :o )Keep us posted....

Guys, I just went out today and tried a 15.00 X 17 prop and what a difference it made. WOT ran 40.3 knots, just over 44mph and the hole shot was much better, planed out quicker too.

WHEW!!!!!!!!!!!!!!! Had me worried there.

Thanks for the suggestions everyone!