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  Intial setback plate height on Montauk?

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Author Topic:   Intial setback plate height on Montauk?
Wild Turkey posted 04-22-2002 03:38 PM ET (US)   Profile for Wild Turkey   Send Email to Wild Turkey  
I installed a CMC setback plate (ML-65) this weekend on my 1989 Montauk (90 HP V4 Evinrude). Can anyone suggest a good starting point for proper engine height? Currently, the plate is adjusted so that the cavitation plate is about 1 1/2" above bottom of the transom.

BTW, before installation of the plate:

40 mph @ 5200 rpm (light load)
19 pitch OMC SS

Can I hit 45 mph?

Thanks in advance,

lhg posted 04-22-2002 04:59 PM ET (US)     Profile for lhg    
That's about as high as you'd want to go. Even at that height, you should be running a "surfacing" performance prop, like an OMC Raker or Mercury Laser, or one of the aftermarket brands like a Stilleto.
Wild Turkey posted 04-22-2002 10:42 PM ET (US)     Profile for Wild Turkey  Send Email to Wild Turkey     
Larry... should I start at a lower setting and work my way up?

The prop is a OMC Rapture...


lhg posted 04-22-2002 11:27 PM ET (US)     Profile for lhg    
"Rapture" is a tradename used by Michigan Wheel, not OMC, but it is a performance prop and should be fine. Start at about 3/4" high, and move it up until you get excess slippage. Just be careful you don't pull the water intake openings above the water flow, or you'll start drawing in air and burn the top pistons. 2 1/2" is about max for most engines and props without high performance water intakes. You can easily measure this distance on your engine.

There are a lot guys on this site who have had experience with your situation.

Bigshot posted 04-23-2002 10:46 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
If already mounted...try it. I have mine about 3" up.
seagull posted 04-23-2002 01:10 PM ET (US)     Profile for seagull  Send Email to seagull     
I have a CMC with a 90 Yamaha mounted on the top engine hole and the jack plate is about 3" up. I may have a 1/2" of travel left and may go up, because I have not blown out at the 3" mark yet. Wheel wash at normal cruise trim is just starting to look about right.
Wild Turkey posted 04-23-2002 02:49 PM ET (US)     Profile for Wild Turkey  Send Email to Wild Turkey     
If anyone is interested.... here are some pictures of the installation:


Bigshot posted 04-23-2002 03:30 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Jack that thing up. I would have started with it up higher on the plate....but too late now. You can go about another 2".
seagull posted 04-23-2002 03:32 PM ET (US)     Profile for seagull  Send Email to seagull     
I have the same jack plate and started out with the engine about the same hight you have in the pictures. Like I mentioned in above post there is only about 1/2" left of travel and the prop has not blown out yet.
Landlocked posted 04-24-2002 04:36 PM ET (US)     Profile for Landlocked  Send Email to Landlocked     
When I had the new 90 put on my montauk, the mechanic mounted it two holes up to avoid the problem with the lower bolt hole in the well.

To check height I set the motor level while on the trailer and sighted down the cavitation plate to make a mark on the hull with a pencil. I then measured this mark up from the bottom of the boat. It is almost exactly 1.5". The motor gets plenty of water at this height but I think if I had it any higher it wouldn't. I can only use a moderate amount of trim without breaking the prop lose.


Wild Turkey posted 04-26-2002 07:00 PM ET (US)     Profile for Wild Turkey  Send Email to Wild Turkey     
I tried out the new jackplate setup this afternoon. Ended up about 2-1/2" above the bottom of transom.

All data by GPS and light load:
WOT - 43.8 mph @ 5600 rpm. A little chine walk and HOLD ON!!
cruise - 31.1 mph @ 4000 rpm

Not bad for a 13 year old Envinrude 90Hp V4.
A sincere thanks to all those that helped!!


Ogden Dunes posted 09-29-2002 11:50 AM ET (US)     Profile for Ogden Dunes  Send Email to Ogden Dunes     

I am thinking about putting a stetback plate on my supersport. I have a Yamaha 4s which is heavier than your application. How much lower did the transom drop compared with no setback plate?


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