Motor Height - Q for 21 SE Owners

[Regulate It]

So after much discussion regarding props and motor height, I am starting with the proper engine height to try and get more rpm out of my 2001 150 Yamaha HPDI motor (currently 4800 WOT turning a 15 x17 OEM black stainless prop). The motor should spin up to 5600.

There are four upper mounting holes on the motor and my motor is bolted to the very top hole. I was wondering if other 21 SE owners with similar motors have the same set up or have it mounted higher. I'm going to drop it in the water sometime this weekend and run it - and check cavitation plate per a discussion with Ken at Propgods. He first suggested checking motor height before buying a prop and just wondering if other members have a very different set-up . Ken also thought a 15 x 15 prop would serve me better - but first step first - Thanks Fellas. Jason

 

[Brad 21se]

Hey Jason,

My 21se has a 150 carb'ed 2-stroke and is mounted at the lowest setting from the factory. I would like to raise it one hole, but will need to redrill the bottom holes due to the way Parker originally drilled the transom. My boat came with a black SS Yamaha prop (17p) and would turn 5000-5100 rpm with 2 on board and a half tank of fuel. I have a t-top/curtains, so that may have a small effect.

After I bought the boat last year, I swapped over the prop from my old Mako. It's a Michigan Apollo SS - 14 3/8 x 15p. I now turn 5400 WOT at about 41mph. I think the 15 pitch works well on this hull with a 150. Very responsive at all RPM's with a great hole shot and plenty of top end. According to my Yamaha fuel management, I get 3.5mpg+ at a cruise in the high 20mph range per GPS.

I had a hpdi on my old Mako and they can lose top RPM's due to a dirty vst filter, fouled plugs, faulty/dirty O2 sensor. I even had a bad injector driver which I replaced. Those engines are pretty picky, but run great when everything is dialed in.

Hope this info helps

 

[Regulate It]

Brad - super-helpful, thank you. I think we spoke about the prop once before. Funny you mention the filters, I just bought all new filters, gaskets, clips etc for changing the VST filter etc. Its bogging a little around 3000-3500 then clears out.

I took a longer look at the boat this morning, and I think I am in the same boat having to re-drill. I'll try filter swap, double check the skeg under power and if its under where Ken suggested, see how much play I have. I may be able to go up one hole, but no more than that. Break out the floor jack time. (per Ken's suggestion - loosen and remove top bolts, loosen bottom, piece of wood under skeg, floor jack up slowly to desired height, 4200 back in upper hole with bolts tighten them all up - probably sounds easier than it will be.). And I thing no matter what I am going to blow $400-500 for a new prop - Ken suggested a 15 x 15 Mercury Enertia with a hub kit.

 

[warthog5]

probably sounds easier than it will be.).

No it is that easy, but I bet your not going high enough.

Starting point would be cavitation plate 1in above bottom of boat with a notched transom.


Guy's......Pix's, Pix's. ........pix's paint a 1000 words......Words are open to interpretation.

This motor is mounted in the 3rd hole....Count down from the top. Each hole raises the motor 3/4in.

 

[Brad 21se]

My hpdi was kinda a PITA until I got things sorted out. If you end up needing an injector driver, PM me as I have an extra one :wink:

Funny you mentioned the Enertia prop..... I tried one last season (got a great deal on a used one). It was the 15x15p. Nice prop and higher tech than the Apollo I am running, but I opted to sell it locally after trying it out. Compared to the Apollo, the Enertia had identical WOT speed and RPM (I was kinda surprised). One big difference was the ability to trim the engine way out since the Enertia has incredible bite at higher trim angles, but I rarely run the boat like that. Overall I liked the mid-range handling of the Apollo better..... I never compared economy since I didn't have the fuel management at that point. Lots of good prop options, but regardless I think a 15p works great on the 21se. Even if you lose a mile or two on the top end, it's really not a speedy hull design.

I'll take a picture of my current engine height this weekend. With the lousy Spring we've had, I'm embarrassed to say the boat is still in the driveway :x

 

[Bigboy]

I have a 21SE with a 150 carb Yamaha. The boat came with the Yamaha 17 inch pitch but with the load I carry, the motor would only turn 5000 rpm. I went to a Propco 15 inch and I'm very happy with the increased performance. WOT with a load is now 5300 and with a light load I can get 5500 and 41mph. The sweet spot with that prop and motor is from 3700 to 4000 rpm.

I raised the motor from the second hole to the third and it seems the performance is up a notch. I only tested the rig once since the change but because or rough conditions, I couldn't compare with the old engine height.

 

[Regulate It]

Thanks BigBoy. I think I have just enough room due to the factory bolt pattern to go one notch, but not two. I am on the first bolt hole and using the starting point measurement from Warthog - its way too low. I hope raising the motor, new prop (15 pitch seems to be the universal way to go) and the planned filter clean out should improve performance. Will post back once its all done, but weather and jobs are getting in the way.

 

[Regulate It]

Well it seemingly took forever to get a new prop to try and get back on the water. I pulled the old 13 3/4 x 17p prop off the yammi and per Brad's suggestion put an Apollo prop - roughly a 15x15 and what a difference. Got up to 5300 rpm from around 4800 and close to 40 mph with a heavy load. Brad appreciate all the advice definitely a worthwhile upgrade.

 

[Brad 21se]

Glad that worked out Seems to be a good match for the 21se with a 2-stroke.

 

[Regulate It]

Brad - I could not be happier. Don't see the need to raise it up any longer. Plenty RPM and speed for me. Thanks again. Jason