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Author Topic:   25" shaft outboard on montauk
Disco Stu posted 02-10-2003 12:22 AM ET (US)   Profile for Disco Stu   Send Email to Disco Stu  
I have found a excellent opportunity to purchase a brand new 90hp 4 stroke merc for my Montauk. There's one hitch: It's a xlong shaft. The seller seems to think I would have no problem using a jackplate to mount the engine 6" or so above the transom. Has anyone had any luck with a simmilar arrangement, and would any of you be worried about having so much weight that high above the waterline? Could that effect the center of gravity causing the boat to be less stable?
Bigshot posted 02-10-2003 09:48 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
I turned down a brand new 115 Yamaha because it was a 25". I do not think it will look right but it can be raised the 5" with a jack plate. It better be a real good deal....I mean really good.
lhg posted 02-10-2003 04:57 PM ET (US)     Profile for lhg    
I would not do it, considering the high weight of the engine. It is relatively easy to have the engine converted back to 20". Get a price on that work.
John W posted 02-10-2003 05:14 PM ET (US)     Profile for John W  Send Email to John W     
I agree with Bigshot & lhg. I believe the Honda is one of the, perhaps the, heaviest 90hp motors available. I ould be reluctant to put an even heavier 25" shaft model on the transom.
Disco Stu posted 02-10-2003 06:08 PM ET (US)     Profile for Disco Stu  Send Email to Disco Stu     
Thanks you guys. I called a Mercury dealer and they said the conversion to a 20" shaft with all new parts would run over 3500 bucks. Though using a used gearbox would be cheaper, I can see that it's still too pricey for my budget.


Sal DiMercurio posted 02-10-2003 10:58 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
$ 3,500 !!!!!
Theres a place in Ohio that makes aftermarket shaft extensions & shorteners.
The cost should be close to $700.00
I don't remember the name of the place, but if you post it on the WMI board, [ boating ], Dunk should know.
Bigshot posted 02-11-2003 11:22 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Uh need to replace the midesection to make it 20", you are not just removing an extention plate and a drive/shift shaft.
lhg posted 02-11-2003 02:44 PM ET (US)     Profile for lhg    
I thought the 3500 was ridiculous also. Mercury does not make a one piece 25" center section for their mid-range 4 1/4 greacase engines. So the 25" 90HP would have a 5" extension kit on it. It should be easy to eliminate this spacer.

That dealer is going to have a hard time selling a 25" 90. There is little demand for them.

Bigshot posted 02-11-2003 03:37 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
I know the 25" Yammie was in the midsection. I believe the OMC/Bombardiers are the same as well as Zuki's. Merc would be the only one still making 25" 4cyls with an extention plate and longer shift/drive shafts. If that is the case why would the dealer quote such a high price? Replacing the shafts can't be more than $1000 with the parts.
lhg posted 02-11-2003 03:54 PM ET (US)     Profile for lhg    
That's what Sal and I wondered. Believe me, Mercury only makes 25" one piece shafts on the V-6's. Check photos on, Saltwater 115's.
Sal DiMercurio posted 02-11-2003 05:45 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Uhhhhh Big shot, In 2000, I had the choice of getting [ from omc ], either fresh water [ blue engine ]200s with 20" shafts, for far less then the saltwater [ white engine ] w/25" shafts.
I looked into it & found the place in Ohio.
They would sell me the extension for the shaft & the mid section & whatever I needed for under $700.
I think the dealer he was talking with, was thinking he had a sucker, cause theres absolutly no way it should even come close to $1,500 compared to $3,500,...."UNLESS" you buy from the manufacturer of the engine.
Aftermarket is lots less.
I got the saltwater engine because I fish salt water.
Sal DiMercurio posted 02-11-2003 05:54 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
IHG, Merc puts 20" shafts on "
LOTS" of their V6 engines.
I live on the Sacramento river in Ca. & every bass boat going 60+ mph is running a 20" shaft on their V6s, even their 280 hp [ says 250, but puts out 280 hp ]comes in 20".
Bigshot posted 02-12-2003 09:13 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Sal we know that! The question is not whether it is easy and cheap to convert a 20 to a 25"(which it is) but how do you convert a 25 to a 20" which may be as simple as undoing an aftermarket conversion or replacing a whole midsection. For instance your fict if a 25" will NOT convert to a 20" unless you are real handy with a plasma cutter.

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