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Author Topic:   Yamaha c90/Montauk Performance Update
compounder posted 06-04-2001 11:36 PM ET (US)   Profile for compounder   Send Email to compounder  
I now have about 23 hours on my new Yamaha and she's off the double oil.

I put about 125 miles on this past weekend and seem to have averaged about 5mpg.

Top speed (gps) at WOT (5300 rpm) in still 39.7mph.

How does this compare with your Montauk/90hp set-up?

Joe

JimU posted 06-05-2001 11:33 AM ET (US)     Profile for JimU  Send Email to JimU     
I, getting 42-44 mph at wot per gps depending on how loaded. Jim
lhg posted 06-05-2001 01:14 PM ET (US)     Profile for lhg    
I think you guys are running different hulls, the Montauk 17 vs earlier 16. Your results confirm what I have thought for some time. The earlier 16 is a faster, lighter (by about 150lbs) hull.
andygere posted 06-06-2001 11:02 AM ET (US)     Profile for andygere  Send Email to andygere     
I get 39 mph out of my Montauk w/ 85 hp Johnson running 13.25x17 prop. This is under ideal conditions, 2 aboard, medium load, and lots of tweaking with the trim.
johnk posted 06-06-2001 06:53 PM ET (US)     Profile for johnk  Send Email to johnk     
1986 Montauk
no bottom paint
2 people
average fishing load
one battery
stock 27 gallon gas tank (full)
2001 Johnson 90hp OceanPro
13.25x17 Rapture cupped prop
33 MPH cruise @ 4000 rpm
46mph WOT @ ~5300 rpm

good luck

john

whalernut posted 06-06-2001 08:07 PM ET (US)     Profile for whalernut  Send Email to whalernut     
I run an OMC 3 blade prop with 19 in. pitch(not sure of diameter) on my 73` `16 Currituck with a 75` 85h.p. Johnson. First off it it runs really fast with 1 person with 12 gal. gas, and moderate load. It runs fast with 2 people with same load. With 3 people it starts letting me know at full speed that I could use a 17 in. pitch! I usually fish alone or with 1 other person, so I believe the 19 inch prop is proper overall on my boat engine combo. If I were to ski someone, I belive with 1 other person in the boat, I would need a 17 in. or 15 in. prop? Regards-Jack Graner.
Eric posted 06-07-2001 09:55 PM ET (US)     Profile for Eric  Send Email to Eric     
My 1962 Nauset has a 90 horse Johnson with 28 hours, and a 13&7/8 x 17 Viper prop (3 blade, heavily cupped). This is another OMC prop, I don't know how it compares to the Rapture prop referenced above. My boat's very light, with one battery, an aluminum 20 gal tank, fiberglass console and a plastic swingback seat. No stainless rails, no windshield. It also may have a bit less wood than the later 16 foot hulls. Fresh gel-coat, no bottom paint. I haven't had a GPS on it yet, but have some experience for comparison, and think it may approach 50 mph. Had a family member out this weekend, she said it's a lot faster than the 45 mph speedboat her friend has. I hope for some real numbers soon. I've outrun some jet skis pretty easily. Lots of fun there, they make a run at me for some wake jumping, and can't catch up!
lhg posted 06-08-2001 12:44 AM ET (US)     Profile for lhg    
Eric - sounds about right to me, and you're using an excellent higher raked performance prop. That's where you're getting the "action". It's probably better than than the Michigan Wheel Rapture, and is more expensive to buy. Those older 16' Whalers fly!
Kelly posted 06-08-2001 11:51 AM ET (US)     Profile for Kelly  Send Email to Kelly     
Are you happy with the "C" model? Would you get the "C" or the oil injected model if you were doing it again? Kelly
Hank posted 06-09-2001 12:30 AM ET (US)     Profile for Hank  Send Email to Hank     
Compounder
You fail to mention in your post what your prop pitch is.
With a 17 in pitch prop your theoretical speed is 42.6 MPH.
With a 19 in. pitch prop your theoretical speed is 47.6 MPH
By theoretical speed I'm referring to moving with zero slip of the prop in the water. Some of the reports in these posts show negative slip. If you can do that I would expect that you will find more fuel in your tank after you've run for a while than you started with.

At 39.7 MPH with a 17 in. prop your slip is in the range of 3.5% to 5.0% . That sounds good to me.

If you're running with a 19 in prop your slip would be 16%. You may need trim adjustment or something else is contributing to drag.

I have an old magazine article which shows tests run with a 1986 montauk and a 90 HP Yam with 17 in. pitch prop. At 5000 RPM they show a speed of 38.3 MPH. at 5400 RPM (WOT) they show a speed of 41.9 MPH.This is an older reference and their data was obtained with radar guns. This is in good agreement with your data.(If you're running a 17 in.prop) They show gas mileage in the 5 MPG range, also in agreement with your results.
Hope this helps you.
Hank

TightPenny posted 06-11-2001 10:24 AM ET (US)     Profile for TightPenny  Send Email to TightPenny     
2000 Montauk
2001 90hp Johnson
17" Michigan Wheel Rapture

Load full 28 gallon Tempo
One oversized Engineer
fishing gear and electornics

WOT 5200-5300 RPM - 37.1 Knots GPS
4000 RPM +/- 30 KNots GPS

bones posted 06-11-2001 04:22 PM ET (US)     Profile for bones  Send Email to bones     
2000 Montauk - 950 lbs
2001 Yamaha 90(oil injection) 270 lbs
Standard 17" pitch aluminum prop
25 gallons fuel
cooler
12+ beers
2 bags of ice
1 person & a few small extras
WOT (5300 rpm) 42-43 mph
This is water by the hull - not GPS

(Although I'd rather run @ 3600)

bones

66Sakonnet posted 06-12-2001 04:34 PM ET (US)     Profile for 66Sakonnet  Send Email to 66Sakonnet     
66 Sakonnet
71 Mercury 1150 with T&T
2 full-size batteries
1 small reserve battery
12Gal Fuel in factory steel tanks
Wooden Center console
wood pilots seat
rear seat
all rails
waterlogged hull (lives in the water)
1 large pilot
1 skinny 1st mate
1 70LB Labrador retriever
standard "fishing gear"
33MPH GPS
maverick posted 06-12-2001 05:09 PM ET (US)     Profile for maverick  Send Email to maverick     
Bones wrote: 2000 Montauk - 950 lbs, 25 gallons fuel, cooler,12+ beers, 2 bags of
ice, etc.

QUESTION: What kind of beer? heh heh. sorry, couldn't resist. Mav

bones posted 06-12-2001 09:19 PM ET (US)     Profile for bones  Send Email to bones     
Dear Mav:

You should know by now...
only the 1st beer matters...
after that...
who cares.

Hey Mav, who and where are you?
I don't see you anywhere on this thread.
What's your boat?

bones

JimU posted 06-13-2001 05:14 PM ET (US)     Profile for JimU  Send Email to JimU     
The beer factor can be a significant variable. Is it a light or heavy beer and what size/type of container? Down here in Cajun land the weight of 12 beers can vary substantially as we call a "beer" anything from a "pony" Miller to a "pony" keg. AHHH--EEEE!!! JIM
simonmeridew posted 06-13-2001 07:29 PM ET (US)     Profile for simonmeridew  Send Email to simonmeridew     
What's the top RPM supposed to be with a '99 Johnson 70 HP low(40) hours on it? My book says 5000-6000 rpm but "check with dealer," whatever that means.

I'm running as follows:
84 Montauk with a little bottom paint
24 gal tank
1 batt
350 lbs of people and gear
13 3/8 X 17 alum. OMC stock wheel
GPS indicates 32 mph, trimmed out well.

Am I over the "red line", if so should I go to a 19" prop?
simonmeridew

whalernut posted 06-13-2001 08:40 PM ET (US)     Profile for whalernut  Send Email to whalernut     
Simon, it seems most people run 90h.p. engines on their Montauks. That said it seems with the OMC 90h.p. engine with certain pitches of props they run about 45-50 mph. So that being said, I belive their probably using 19pitch. props? You said you are getting 32mph. from a 70h.p. Johnson with a 17pitch. prop. I think with a light load you may get a few miles per hour out of it? That being said, you may not like the performance from a 70h.p. with a 19 pitch prop with any moderate to heavy load? The 70h.p. 3 cylinder is much less powerful that the 90h.p. V4. The big V4 swings the 19 pitch prop with a lot of power! The 70h.p. might need some help in the 17 pitch? I don`t know how much you would benefit from a 19 pitch prop? Anyone else have any ideas? Regards-Jack Graner.
Erik posted 06-13-2001 09:24 PM ET (US)     Profile for Erik    
Remember that a 15 with a 70hp gets around 45mph. A 17' Montauk is harder to push but it should 35+mph with a light load(you,gastank,anchor),if i where you i would get a 17pitch stainless steel cupped prop and if you can find a little smaller diamiter it should be a good combo.-Erik

PS- I also would not recommend a 19pitch.If anything you want to go down maybe a 15pitch SS with aggresive cupping.

Lil Whaler Lover posted 06-13-2001 09:38 PM ET (US)     Profile for Lil Whaler Lover  Send Email to Lil Whaler Lover     
Gentlemen, You cannot compare the pitch of propellers for performance when comparing the OMC 70 to the OMC 90. They have different gear ratios in the lower unit, the 70 has a 12/29 and the 90 has a 1/2. Each size must be propped to its specific uses. Yes they do share the same size propellers but the speed potential with the same pitch and the same rpm will be about 17% slower on the 70. Dave
simonmeridew posted 06-13-2001 09:39 PM ET (US)     Profile for simonmeridew  Send Email to simonmeridew     
Thanks for all replies. Any particular brand or style aggressive cupped ss prop? Any suggestions?
Still wondering about the 5600 rpm.
simonmeridew
Erik posted 06-13-2001 10:55 PM ET (US)     Profile for Erik    
Are you running at 5600rpms, you didnt mention that before. According to my Johnson cataloge your well within rpm range of 5000-6000rpms.
Well if ur runnin at 5600 then stick with your current pitch. As far as what prop to buy, I would go with a OMC Viper. I have heard only good things about those props. If you go to www.a1discountprop.com you can find some great prices too. When you get there go to OMC and look under your engine catagory. Also check out umm... http://www.evinrude.com/info/parts/props/allprops.html A Viper 13 7/8 x 17 sounds good. For something cheaper Powertech is good too but remember you get what you pay for.
Bigshot posted 06-15-2001 03:50 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
My 15 sport CC with a 70hp Johnson mounted high, trimmed to the hilt(5' tall rooster tail) and a 21" SST would GPS(i swear) The best at 46.7 mph. It ws downright scary due to chine walking. My 17' Montauk with a 115 Johnson mounted stock and a 19" alum would do about 43-44mph. With some tweeking and a SS prop 46-48 would be possible. I raced a guy in a new 17 with a C-90 and we were about neck and neck. He was running a 19" SS prop so I would say 43+. I just bought one todayso I will let you know(17 w/ 90Yam).
Seabrook posted 04-02-2002 10:29 PM ET (US)     Profile for Seabrook  Send Email to Seabrook     
1983 Montauk, 27 gal fuel, two adults, too much gear, pushed by a 1982 Johnson 115. Motor was original on the boat and still strong. I added a hydrolic jack plate and have a dolfin. RPMs were too high with the 17", so had had repitched to a 19". RPMs still to high, so bought a Johnson SST 21" pitch. Hole shot is slower, but still planes quick. Working the T&T and the Jackplate, WOT at 5800 RPMs and 48 MPH. My 115 still runs perfect but has way too many years of salt. I too am looking at repowering with a newer 90HP motor.
Salmon Tub posted 04-03-2002 10:04 AM ET (US)     Profile for Salmon Tub  Send Email to Salmon Tub     
In reference to Hank's post, I guess almost a year ago now, I too have experienced with my 90 (nissan) that at certain ranges the actual speed will over-exceed that theoretical speed. No clue why - act of God, natural phenomenon, extra-terrestrial intervention... In any case, I think that first, with cupped props, the pitch is a reference more than an absolute (even though stated in inches), I.E. you buy a size ten shoe - what ten inches, ten centimeters..., also, there will always be some discrepancy in measurement. When you drive a car, you put on the Cruise Control and it goes steady. I have never been able to get neither my GPS nor my Speedo (paddle wheel style connected to fish finder) to hold a steady speed, always +/- .1 to 1.0 mph. In reality the real deal is: two Montauks leave San Francisco Bay at the same time with the 90 HP engines, same size props, but different engine makes. both proceed to run to the Farallon Islands at WOT. The distance is approximately 27 miles. The faster boat traveling at 45 mph will get to the Islands in about .6 hours or 36 minutes. The slower boat, traveling say 40 mph will get there in .675 hours or 40.5 minutes, four and a half minutes later. Both boats will have beat the #@!&* out of their respective passengers. The moral of the story is it really does not matter for practical purposes. Now, on the other hand, if one of those 90's say puts out a real 94 HP, and the other puts out a real 86 HP, though both are rated at 90, then that is a different story, would take a lot of time and money to squeeze out a few more horses.
Eric posted 04-03-2002 10:22 AM ET (US)     Profile for Eric  Send Email to Eric     
It's interesting to see this thread come around again. Here's an update on my 1962 16 Nauset with 1999 Johnson 90. Now rigged with a windshield/grabrail on the console, also 1 battery, 20 gallons fuel, 2 anchors, lots of fishing tackle, icechest and ice, 14 gallon baitwell, and one person.
With GPS, I've hit 44, but get a reliable 42 to 43. Still have the 13 3/8 X 17 OMC Viper. It turns about 5600-5800 rpm, so I'm still underpitched and am having the prop repitched. I thought that this prop would be perfect as I added weight, but the torque of the V4 seems to ignore the added load. I've turned 5700 rpm with three people in the boat. I also still have the engine mounted all the way down, and will be raising it (one hole?)when it next goes for service. Looking for a few more MPH with the repitch and raised motor, from what I see above I suppose about 45-48 would be possible on this light weight hull.
compounder posted 04-03-2002 09:41 PM ET (US)     Profile for compounder  Send Email to compounder     
I've gotten so used to having my sun top up almost all the time that I didn't even think,until recently, that it probably has some effect on my top speed.

Though I have a complete Mills setup, I usually use a much larger, custom made top. Seems to me this would have to lower top speed somewhat.

I haven't had the old girl in the water since early winter, but I'll provide some more stats soon with the top down.

Anyone else out there have some numbers top up vs. top down?

Bigshot posted 04-04-2002 01:45 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
That was my second post here on the 1st day i registered and bought my current 17'! It is a tearfull moment;)

Being a ways back i would say my 17 with a 90 Yamaha did the best of about 41.5 with the GPS running a 13x17 OEM SS prop. My 70 4 stroke does about 2mph less and burns half the fuel. Nah nah na nah nah!

Glad to see I am still obnoxious!

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