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Since everyone was posting their speed, i figured I would check mine out on the GPS. I am 36-38 with me and my buddy. This is with just 12 gallons and minimal gear. The motor is a 96 Mercury 90.. I figured I should be in the 40s from what I was reading earlier. My RPMS are at 3500 or so, bu I think the tach is on the wrong setting. The mechanic looked and said the prop should be fine. Before I changed the tach, I was right at 5000 rpms, so I think the tach is just reading wrong. Either way, should I be in the40s, or am I okay? From what I can tell, water in the hull should not be an issue.

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I have an '87 Montauk w/ '87 Merc 90hp and was running 38 mph in a small chop yesterday. Also had a 12 gallon tank, single battery, 9.9hp kicker motor, and one buddy in the boat. Don't have a tach so not sure what the RPM's are running. Seems we have pretty comparable rigs, with comparable results. I think w/ glass flat water she'll run a 40.

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I got 39 mph on the GPS at 5400 rpm the other day in a light chop with 4 people, 20 gallons of fuel and a 6HP kicker on board. I got the last 1 or 2 MPH by playing with the tilt trim. I have a 76 Montauk with a 1995 Johnson 90. I'm not sure what the prop is- it as an aluminum prop I got with the boat.

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My 1982 Montauk with a 90hp Mariner was maxed out at 42.3 mph 36-39 with extra people..

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36 to 38 MH is way too slow and indicates something is wrong. That boat/motor combination should do 40 to 44 MPH depending on how it is rigged.

What details can you offer? Motor mounting height? prop? Bottom paint? Hull weight? Accessories installed? Typical conditions?

If you formerly were hitting 5000 RPM and now only 3500 RPM, then the motor is not firing on all cylinders or something more sinister is happening.

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My 2010 170MT goes over 42 mph... 90 4stk

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I have a Johnson Gt 100 V4 and maxed out at 58 mph (according to GPS) while riding by myself.

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single person down hill with a (2000 year) Suzuki DF 70 14x19 pitch cupped GPS speed 36mph

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I have seen 42 MPH per a GPS at 5100 RPM with a 19K series SS Yamie prop. Mounted flush on the transom

Someone above this post said 58 MPH... WOW... My 17 would blow over backwards in a light gust at that speed...:-)

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58 mph with a Johnson GT 100 V4 on a Montauk is total BS.

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Must of been riding down hill with GUts LOL
1972 Cohassett 115 Yamaha 50 mph flat calm. BG

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For those of you that don't know what I meet by ("down hill" ) This term is used here on the left coast with the swell behind you giving you a push. And up hill would be just the opposite headed into the swell, Wind is also a factor, which I had had at my back when I took this speed reading. I'm not trying to be rude, I'm posting this because some people never get on the ocean and are unfamiliar with this term. Reporting there speed on flat water in a lake or something like that. So my reported speed (36 mph) would not be the same on flat water.

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I got mine up to 65 this morning... pulling it on the trailer.

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hc...thats a good one

'87 17 mtk w '95 115 evinrude gps'd at 43 at 5200 rpm
me and another, 20 gallons and 2 batteries in a light chop on the bay

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89 Newport with a 2005 ETEC 75HP, 38MPH at 5,000 RPM. 12 gals gas minimal load.

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Agreed on the 58mph being impossible with a GT 100. We only saw 48 on our Montauk with a Inline 6 Mariner (Mercury) tower of power which was know for it's strong, if not underrated horsepower ratings. Granted we were only turning an aluminum prop but there is no way we would have seen 10 more MPH.

On this past Monday I was finally able to log a full set of numbers on the 1976 17' Newport and the 1974 85hp Evinrude Starflite turning the OMC SST 13 3/8" x 17. Motor is mounted all the way down.

The air temps were in the low 70's and so where the water temps. Water conditions were a light chop and slight breeze. Boat had 16 - 17 Gallons of fuel.

2000: 8.5mph
2500: 13.8mph
3000: 20.5mph
3500: 25.6mph
4000: 30.8mph
4500: 34.7mph
5000: 38.4mph
5175: 40.3mph (WOT trimmed all the way out)

After seeing others numbers I am over the moon happy that my 36 year 85Hp powerhead (not prop) rated motor performs like it does.

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GPS speed does not actually give us SOW, Speed Over Water unless there is absolutely no wind and no current.
GPS gives us SOG, Speed Over Ground.

If our boat is doing 48 mph over the water and we have a 10 mph down wind speed or current, then the GPS display will tell us we are going over the ground at 58 mph.

To get the SOW accurate, we need to turn the boat around 180º and run the same test going upwind or up current and then average the two speeds.
In this example, going 48 mph over the water and into the 10 mph wind or current, the GPS display our SOG would be 38 mph.

So, GPS one way says we are going 58 mph over the ground.
GPS the other way says we are going 38 mph over the ground.
Average boat SOG, Speed Over Ground is 48 mph...
This gives us our boat Speed Over Water and the top speed our boat can do if we were running this test at WOT, Wide Open Throttle both ways...

So, to be accurate, you absolutely need to run your speed test in both directions and average these speeds.
Otherwise, any test you do is NOT accurate and you could just be blowing in the wind so to speak.

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WOT on my 03' montauk 170 is 43mph, by myself, fishing package and pads, single battery with bimini down (e.g. minimal equip), minimal swell, no wind (early morning) on inshore ocean at 5400 rpm (merc 90hp 4-stroke), lightly trimmed up.

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'81 Montauk with 1998 2 stroke 75 HP Merc. with gear. Does about 34 (with two 12 gallon tanks) but cruises very nicely at 25-28. I don't think I would want to go 45 in a Montauk on Puget sound.

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39.7 MPH (per GPS) @ 5300 RPM in glassy water with me, my girlfriend, and about 18 gallons of fuel on board. l'm sure the boat would do well over 40 if I could get it to run flat. These old V4 'Rudes pack some punch.

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I am the original owner of a 1989 Montauk 17 rated for 100-HP that's been running with a 1990 Yamaha 130hp since new 20 years ago. It runs over 50-MPH and will deep start 240-lb slalom skier with three adults in the boat on a 21x13.25 original SS Yammy prop. The Yamaha is about at end of life and, since no manufacturer has a 130 at comparable weight, I've ordered an E-TEC 130. The MONTAUK has always been dry stacked. I took it to the landing and pulled it out to wait on the new Evinrude to arrive. The dealer is supposed to call me in a few days for install.

GPS clocked the MONTAUK at 58-MPH running with the tide and 55-MPH against tide at 5,600-RPM for her last run on the Yamaha before the transplant. The original SS Yamaha propeller is 21-inch pitch. I have a 23-inch chopper from an old Allison/Merc setup I used to have that has pushes it just over 60 without hub exhaust, averaged up and down current with GPS. I am hoping to get the same performance from the E-Tec.

I'll keep you posted as this adventure progresses.

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I was the original poster of the GT 100 pushing the montauk 17 at 58 mph. There was definitely wind that day and that was definitely with the wind- but it also went over 50 mph into the wind as well. Sounds like this gentleman has gone pretty fast too in his Montauk. I am only a 165 lb. guy- and I was also the only one in the boat- and it was recorded on GPS- so even if it was "over the ground" speed- it was still pretty fast- and the rpm's were at 5600. Not sure why we have so many critics, unbelievers and otherwise out there.

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Huntingturkey,

There are people who are doubting your claim because they have run performance figures on your hull and engine and the numbers did not add up.

Using Crouch's planing hull calculator a Montauk style hull needs 130 HP to attain 58 mph if the boat had a total weight of 1500lbs. Given a dry bare hull of 900lbs and 300lbs for the motor and 165 lbs for you, 50lbs for the battery, 50lbs for the fuel and 50lbs pound for other gear (seat, console etc...) you might be at 1500lbs. If you went to 1600lbs you would lose 1 mph calculated. By the way if I change the HP to 100 the MPH drops to 50.

Using your motor RPM of 5600 RPM, 2.00:1 gear ratio, estimated slip of 6%, to attain 57 mph you would need a 23 pitch prop. A 21 pitch prop would hit 52 mph.

I am not saying you did not see what you saw. I am just explaining why others may not believe you. It is purely that the numbers do not support the result. Sounds like you have a very light hull or a very high pitch prop, or an inaccurate GPS or a very hot motor or maybe some combination of the above. In any case it has nothing to do with you as a person.

Regards.

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I would be careful with mounting a motor which is over what is rated. I am surprised a dealer would even install that for you. If you get pulled over by the coast guard, there would be big trouble so be careful.

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I thought this seemed rather odd with a boat rated for 100 HP and a 130 on it. I always wondered what, if any, penalties there might be. I have also envisioned the much over rated motor tearing the transom right off the boat on a hole shot.

Correct me if I am wrong here but I don't think the design of the Montauk hull was ever meant for pure break neck speed and right around 40 MPH seems like about enough.

I'll be fine with my Montauk doing 60 behind my truck!

Gary

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Getting back to my original problem, I realized my tach was not set right. It was set on 20 poles, and I believe it needs to beset on 12 poles. I still get the same speed, but now I can see where my rpms are. I will let you guys know the results hopefully this weekend.

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As a note, my 17' Montauk has had a 130hp Yamaha 2 stroke on it for over 20 years.
Needless to say, I've been "checked" by both DNR and Coast Guard at least twice a year. No "official" has ever said a word about the horsepower. My new 130hp Etec is being rigged as we speak. I will probably have it Saturday or Monday.
I'll post as soon as I have new performance results.

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Well bad news unfortunately. I went out after setting my tach right trying to get the rpm readings. While at full speed the motor shuts down. I have no idea why, and I limp back to the dock. When I take off the cowling, my heart sinks. I was sure I added oil before I left, but I didn't. Moral of the story is always double check your oil!! I threw a rod and my mercury is done.

On a side note, if any of you have a late model 90hp you know of let me know!!

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OK..130HP E-tec 1989 Montauk BW now installed. One day (4 hours) of shake down to get past the double oil "break in" and then, today, ran it with GPS. Air Temp 85F, cooler by 8 degrees than the last run on the 1990 130Hp Yamaha. Winds 15mph.

21"x13 Michigan Prop. 53mph against the incoming tide and 56 with the tide. The wind was against the down tide run.

RPM was only 5400 trimed out to the absolute ragged edge. Tech at the dealer says it should pick up a few revs. The Michigan clearly has more blade surface than my old 21" which had been reworked for minor dings over the years and cupped.

This weekend will try pulling deep water starts with 230lb slalom skiier. I have to get my 23" Chopper set up for the Evinrude, probably a week before I get that done.

BTW...at idle this thing is VERY quite and smooth. The loudest noise is the water from the pump hitting the river when out of gear idling. When the "Tuned Exhaust" valve switches on it feels like you've downshifted into "passing" gear.
Will keep you posted.

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Test video running 21" Michigan Prop. 55mph Max, Temp 63F Will be testing addtional props soon.

http://www.youtube.com/watch?v=cWXiHQ0pYoo

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Saw video. That's movin'

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It depends on where you live, I guess. As far as I know, the CG does not specifically prohibit exceeding the max. hp recommended by the manufacturer, but some states and local jurisdictions do have laws against it. You could also be subject to general "unsafe boating practices" laws, if the Coasties or the local Harbor Master really want to bust your chops. Insurance companies don't like overpowering much, either, and they will up your premium substantially if you run an engine that's "too big", if they write you a policy at all.
Of course, you can always use a little subterfuge to keep the LEOs off your back. For years, a neighbor of mine ran an Evinrude "90" with 140 guts inside on his Montauk, and I've known others who have simply switched engine covers or decals to hide what they're running.

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Finally got my prop/speed/rpm headaches resolved with an old SST 13 3/4 x 17. Swapped it for the old 13 x 19 aluminum which only gave me 4600 WOT. I now gwt 5400 WOT and an average SOG of 39.4 mph (I only ever move at 21 mph @ 3000rpm so speed doesn't matter to me. In the testing process my drive shaft snapped, right at the point it enters the housing. My mchanic convinced me to go with a brand new lower unit available from an outfit in FL for $895 (with a 3 year warranty) and he's charging $150 for the swap. It comes to just a bit more than if I would have replaced the shaft, and the new one has a state of the art two=piece shaft. All I can say is thank goodness it didn't happen in one of my usual haunts which would have been over a wreck about 10 miles out in the Gulf...Ralph

PS - regarding overpowering your boat...it's like anything else that's not kosher (cheating)...great until something happens...then all heck breaks loose...ask Tiger, or one of the bass pros who was suspended for life trying for covering a higher powered engine with a hood from a lower rated outboard...these things have a way of catching up with you...be careful.

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1975 Montauk( old hull currituck converted) 1988 Johnson 88 ( a 90 without oil injection), 19" SST II, very light and trimmed all the way out-50 mph. Sea level, 70 degrees F This motor seemed slightly more powerful than other 90 JohnRudes. Just bought 1990 Montauk, 2000 Johnson 90 (not ficht) 19" SST II that runs 46 mph, freshwater 600' MSL, 2 adults, not much gas, with a cavitation plate mounted whale tale dragging in the water at 60 degrees F. I have been in numerous 17's and a good 90 mounted and propped right should run mid to upper 40s trimmed out. just my 2 cents worth

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Van...I agree with you on the speed expectations but my Montauk just wont get there...40 is tops. I do carry dual HD batteries plus 24 gallons fuel, 300 ft. anchor line, tool box, full ice chest and usually almost a dozen rods or half dozen dive tanks plus gear. That may have something to do with it. In any case, matters not, 20 - 25 mph at 3000 - 3500 rpm is all I ever need or can use with the usual chop I'm in.