Max speed on a 150

[MikeD]

As mentioned in in previous posts, I'm breakin in the yam 150 on my new 2120 DVSC. I'm at a point (hour-wise) where I can run her at full, but not more than 5 minutes at a time. Yesterday, it was a little windy and at full throttle she got up to 30 knots. Is this about right? Just curious if other 150hp 21's are in this range.

Thanks

 

[zebpwgc]

i would get about 30kts on my 2004 2120 with carb 150. a little higher with low fuel.

 

[Ranger Tim]

What rpm were you turning? I turn 5700 max with a light load and get as much as 37 mph in calm seas. A more typical fully loaded trip would see 5500 rpm at 33 max mph. My motor took a while to come up to this point. Propping it correctly was key. I started out not getting above 4900 rpm and I had to "learn" the tabs. I wasn't getting out of the upper twenties either. It really doesn't make that much difference to me, except as a performance barometer -- It should run at the right rpm to prevent motor damage. It should also handle good as well.

Are you running a four or two stroke?

 

[andertonm]

Our 2120SC would do about 32-34 MPH under optimum conditions with the 150.

 

[MikeD]

Its a 4 stroke. I took her out yesterday to play with the trim a bit, and got her up to just under 32 knots, which registered 36 MPH. Ride and steering were smooth. I started with tabs in the bow up position, and power trim down(in). Kicked her in the but and gave a few bursts on the power trim up. The steering got a lot smoother, then I borught the bow down a bit and leveled it off. Great ride.

 

[johnsw]

I've got the '04 2120 with 2 stroke carb 150. Calm conditions and trimmed just right (tabs and engine), my max seems to run about 38 mph GPS speed. Engine speed is 5700 - 5800 RPM. Running the standard prop (14-1/4 x 16, I think).

John S.

 

[greatcir]

My new boat, 2007 2120 SC 150 4s, would turn 5,700 RPM and run 38-39 MPH with the factory prop and almost a full tank of fuel and just me aboard. I had to have the motor and the trim tabs down to get on plane quickly and then fool with them both to get the best performance. I bought a lighed gauge for the Lenco trim tabs and could then record settings, but still a lot of monkey motion.

I just finished a series of tests and the bottom line is I do the best with:

1.Cobra plate bolted under the cavitation plate, I can plane without using the trim tabs (need to trim motor down almost half way) with this plate and looks like I lost 1 MPH and only a few RPM to do this. It also holds plane at lower RPM's than without the plate. But I do not have to fool with the trim every time I come out of the hole. I did try the Stingray plate bolted on top of the cavitation plate and it was a waste of time.

2. The Yamaha 14.25X16 SS 3 blade prop is very good over conditions from a full tank of fuel to less than half a tank. I ran a variable pitch four blade (14.5X15 to 21) composite ProPulse prop at the various pitch setting. At 18 inches of pitch it ran 36-37 MPH and 5,600 RPM which was the best setting for it. At 21 inches it did not want to plane. At 15 inches it would go over 6000 RPM but ran slower (had more slip).

I had (20) five pound lead bars I moved around while testing too. They helped keep the bow down when in the anchor locker before I put on the Cobra plate. Then I removed the bench seat and put in a pedestal on the port side which removed about 100 punds so I put the lead bars on the port side to stay trimmed at idle. After I moved tools and other items around I can stand a slight list to starboard with all the lead bars off the boat. A pasenger on the port side is perfect for me now.

So I'm keeping the composite as a good spare set on 18 inches of pitch. (West Marine would take it back if I chose to return it) The hub is guaranteed and each of the blades is replacable. And I know the 14.25X16 3b SS is a good prop for my boat. Now come out of the hole with no trim tabs then just trim up the motor as it comes on plane. At WOT getting 38 MPH & 5600-5700 RPM. My boat will start to porpoise at WOT if the water is slick calm so then I can add trim tabs to dampen it out at some loss of speed or I can slow down a bit too.

Sorry to run on so long .......................Pete