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ContinuousWave: Whaler Performance
Prop for 17' Montauk with 90HP
|Author||Topic: Prop for 17' Montauk with 90HP|
posted 04-02-2000 11:41 PM ET (US)
I have a 1998 17' Montauk with an 1997 Evinrude
90HP carbureted two-stroke. The boat is primarily
used as a dive boat, usually with two
people (340 pounds) and 200+ pounds of
dive gear. Some times there is a third
person with another 100 pounds of dive gear.
Occasionally we take it water skiing.
I'm not interested in top speed but rather
in holeshot (starting the skiier and up
big swells) and gas mileage.
The boat came from the dealer with an
It's annual bonus time, and I'm thinking
posted 04-08-2000 12:22 AM ET (US)
I currently own a 1998 17 Alert with a modified Montauk console and a Mercury 75 2-stroke. With a light load trimmed out it will turn 5600RPM at 35.3 knots. A more normal load of fuel and fish will give 5300RPM and 32 knots. I have tried 6 different props and have found a Ballistic 13.25"x19" the best. Very good hole shot, very good top speed, and little cavitation.
posted 06-25-2000 09:33 AM ET (US)
I think you could use a 19 or 21" prop. The Alert is heavier than the Montauk. With a 90Hp on my 17' and a 19" prop, I can turn over 6000 rpm lightly loaded which is way too much.
I've ordered a 22" which, by my calcs, should be perfect and should develop 50+ mph.
Steel will give you better performance at the same pitch for a couple of reasons: the blades don't flex under load, so the prop retains it shape, and 2) the blades are thinner (compared to an aluminum prop) so they have less drag in the water.
Usually the manufacturers (OMC, Merc) make very high quality props compared to the aftermarket ones sold by the discount houses. Most dealers will let you try props to get the proper size and performance.
posted 07-01-2000 08:22 AM ET (US)
Well, I've installed a 22" pitch Laser II Merc prop on my 17' Montauk with a Merc 90 HP Outboard (both Year 2000).
I can turn 5200 rpm lightly loaded and the boat is doing 39 knots.
The next lower step in the Laser II series is 20", probably too low. But I think a 21" prop would work as well and give the same top speed.
posted 07-02-2000 06:42 AM ET (US)
wds, You don't say how boat was loaded when you tached 5200rpm. If lightly loaded, then you need to drop to a 20" pitch... your engine is rated a 5500 rpm at WOT (trimmed out) and dropping 2 inches should get you 5500- 5600.... right on the money! An inch of pitch (up or down) generally nets 200rpm (up or down..).. You will get better hole shot, highter top speed and better fuel mileage as well as a happier engine with longer life.. happy Whalin'... Clark
posted 07-03-2000 09:04 AM ET (US)
I should have mentioned that the above is a general "rule of thumb" and may not work out especially if prop type/style/manufacturer etc, is changed in the process.. apple to apples..etc..etc.. BigZ just reminded me of our experience on his 27 "Amy's Whaler" with twin CR Yamahas... his top rpm was 5000 with stock yamaha 19" pitch ss props... he dropped to 17" pitch "PowerTech" Yamaha/Merc ss props and , bingo, still only 5000 rpm! Only thing we could figure was that blade design may be different,,, etc.. etc... Anyway, he needed a spare set of props but I thought (and so did the local Yam dealer) that he would pick up 5-600 rpm.. So testing is the only way to be sure... don't want to steer anyone wrong here... Happy Whalin' .. Clark.. Spruce Creek Navy
posted 07-03-2000 09:09 AM ET (US)
Whoops, another mistake! I should have said 4-500rpm! Well, guess it's just one of those days, week, etc.. will take a break and go sit a Whaler for awhile... that should straighten me out! Clark
posted 07-25-2000 07:06 PM ET (US)
I just purchased a 99 leftover 17 standard with a 90 hp merc (2 stroke). It sounds to me like a 20" Laser II is the right prop to obtain the 5500 rpm operating speed. Has anyone experimented with elevated engine heights? I was considering raising my motor a hole or two.
posted 07-25-2000 07:48 PM ET (US)
Merc Laser props are meant to be run at an elevated transom height, minimum of 1 bolt hole up (3/4"), maximum of 2 (1 1/2"). They give reduced performance when run totally submerged.
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