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Author Topic:   115 Merc 4s re-power on Montauk 170: WOW
Marsh posted 07-18-2004 10:11 PM ET (US)   Profile for Marsh   Send Email to Marsh  
On this past Wednesday, I picked up my 2004 Montauk 170 after re-power to a 2005 model Mercury 115 HP 4 stroke EFI engine. All I can say is WOW! I am much more pleased with the boat's performance now. Especially in the 3500 - 4500 rpm range. With the 90 hp engine, WOT would bury the tach, but speed per my brother's GPS was only about 41 mph. It did not handle all that well at lower to mid rpms( 3000-4000) either. All is different now.

After break in on Wednesday and Friday trips, I wrung her out pretty well today. WOT now is only about 5800 rpms (still tinkering with trim settings), but performance in 3500-4500 rpm range is outstanding. WOT speed is probably faster than I usually want to go, except on mirror glass lakes. But it's nice to be able to out run those pesky pontoon boats for a change! I don't have a reading for new top speed (no GPS), but it's plenty fast for me. I'm still running the stock SS prop from the 90, but will experiment with others as I get the chance.

I'm lovin the 115. Whaler shoulda made it stock, IMHO.


dogfish2 posted 07-19-2004 02:55 AM ET (US)     Profile for dogfish2  Send Email to dogfish2     
I totally agree. Made the switch myself and what a difference the EFI makes! It is a much smoother running engine and idles without a burp.
erik selis posted 07-19-2004 05:01 AM ET (US)     Profile for erik selis  Send Email to erik selis     
Glad to hear you are pleased with your motor now Marsh.

What does it cost to upgrade if I may ask?


imko posted 07-19-2004 04:26 PM ET (US)     Profile for imko  Send Email to imko     
Do you have more information about this engine?
What is the fuel comsumption comparing to the 90 4-stroke?
I have a 90 4-stroke, and replaced the Vengeance(13,25x18) prop for a Trophy (13,75 x 19 4-blade)
The mid range (3000-4000 rpm)improved
a lot, but is very hard to handel on high speed.(to much bow lift) The gear ratio (2,33:1 for the 90 4-stroke and
2,07:1 for the 115-4 stroke)is better for the Vengeance
prop. I think if you replace the Vengeane for a Laser II,
(13,25x20)the mid-range is improving a lot !! (± 2800-4000 rpm) Also you can use vent plugs with this prop for better hole shot.
What is the top speed with the Vengeance prop ? (with the
115 4-stroke EFI)



Maximus posted 07-19-2004 10:45 PM ET (US)     Profile for Maximus  Send Email to Maximus     

Glad to see you are happy with the 115. However, I would like to make the point known that the carbed 90 4stroke is still a wonderful motor for the Montauk 170. The motor starts with no choke and with ~half a revolution of the flywheel. Idle is rock solid and as quiet as can be. Fuel consumption has been a consistent 4.5 MPG.

Power from the 90 is more than adequate. Top speed with the 90 is 42MPH. This is right on with what my old 16'7" would do. Hole shot performance is a bit doggy but power comes on fast and furious at higher RPMs. This is the where I could see the 115 EFI being a benefit. Cruising speeds at 6 MPH at 1800 RPM and running at 4000 RPM gives 26-27 MPH.

AQUANUT posted 07-19-2004 10:46 PM ET (US)     Profile for AQUANUT  Send Email to AQUANUT     

WELCOME TO THE 115hp 4s Montauk 170 CLUB!

my 115 hp 4s turned 6100 out of the box....
mercury rep told us that the 115hp doesn't really come alive til your at 5500 rpm...with WOT @ 6000 rpm..I turn 6100 WOT at 6200 I hit the rev limiter and start dropping cylinders..I actually fine adjusted my throttle cable and linkage to get the 6100 and no more.


NOGAR posted 07-21-2004 10:13 PM ET (US)     Profile for NOGAR  Send Email to NOGAR     
Where can I buy a new Montauk and have a 115-HP four-stroke motor installed?
jimh posted 07-22-2004 08:12 AM ET (US)     Profile for jimh  Send Email to jimh     
The Boston Whaler 170 MONTAUK is sold at authorized dealers. Arranging to purchase it with a 115-HP engine would have to be negotiated with either the selling dealer or perhaps with another engine seller.
LHG posted 07-22-2004 06:21 PM ET (US)     Profile for LHG    
If you really want that boat to move, put a Mercury 115 2-stroke on it. This engine consistently outperforms the 115 4-stroke. See published Nantucket performance comparisons.
Marsh posted 07-22-2004 06:46 PM ET (US)     Profile for Marsh  Send Email to Marsh     
To answer some questions...

I still don't know top speed (no GPS), but I out ran a jet ski last weekend. (Whether he actually knew I was racing him was another question, LOL)

Fuel consumption may be a bit more than the 90, but it's hard to tell. The 115 is so much more fun, I operate it in a much more "spirited" fashion.

No doubt, the 90 4 stroke was adequate. No argument there. But that's all it was: adequate. Here in the lakes of east Tennessee, with all the bass boats and jet skis running around, if your boat can't do 50+ mph, you get left behind. With my 90, the only crafts I could keep up with were pontoon boats.

Erik, Nogar:
I traded my 2004 model 90 to a local Mercury dealer for a 2005 model 115. One model year newer engine. He did all the de-rigging, and the re-rigging. One day turn around: in one afternoon, out the next. Total cost for trade up, rigging, and taxes (9.75% here) amounted to right at $2,700. Lots o' bucks, I know, but if I keep this boat as long as I intend to, I will be glad I did the trade up.

The 2 stroke may be a good option as well. But for me, I wanted the clean burn, the quiet ride, and the freedom from oil mixing of the 4 stroke.

I will look into throttle cable adjustment, I have run the 115 a few more times now, and have not yet been able to hit 6,000, despite trying various throttle, trim/tilt settings.


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