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Author Topic:   Montauk: Repowering with 90-HP Mercury
Landlocked posted 02-26-2002 03:27 PM ET (US)   Profile for Landlocked   Send Email to Landlocked  
Well - after two years of talking about it, I just did it. Dropping my Montauk off to be fitted with a new 90 hp 2-stroke Merc tomorrow. Solved the problem of removing it from the trailer as well. They will move it to one of theirs so I can work on mine while the boat is in the shop.

Quick question - I need to let the mechanics know what set-up I want tomorrow. After going back through the posts from the last two years, I see that almost unanamously everyone recomends mounting 1-hole up. Could not find a consensus on prop though. I see recomendations for everything from 17-22 [inch pitch].

Primary "need" - fuel economy and top speed. Will do very little if any skiing. Mostly cruising and fishing. Average load - 24 gallons fuel, 500lbs people dog and gear.

Any suggestions?


scottfarm posted 02-26-2002 03:39 PM ET (US)     Profile for scottfarm  Send Email to scottfarm     
In my opinion, for the money you got the best performing motor you could get for your montauk. I have a 75 hp merc which is exact same engine(weight, bore and stroke) except for hp. I have mine mounted 1 and 1/2 inches above bottom of transom with doel fin. With the proper set up you should get 50mph out of yours. Clark Roberts had the 90 hp on his montauk and could advise you as to what prop to use.
scottfarm posted 02-26-2002 03:41 PM ET (US)     Profile for scottfarm  Send Email to scottfarm     
The cavitation plate is one and 1/2" above bottom of boat.
Landlocked posted 02-26-2002 03:53 PM ET (US)     Profile for Landlocked  Send Email to Landlocked     
Thanks Scott - The vote of confidence helped that sick feeling I have in my stomach right now.

The folks on this board have helped so much with my decision making process. Wouldn't have know where to start without the help I got here.


llewellyn posted 02-26-2002 06:30 PM ET (US)     Profile for llewellyn  Send Email to llewellyn     
My 2002 90 hp Saltwater Merc. 2 stroke( I really like this engine!) was initially mounted so that the anti-cavitation plate was about 1 and 1/2 inches above the bottom of the transom. Had significant problems porpoising and feeling out of control. At 20 hour service engine was lowered to "1 hole up". Anti-cavitation plate is now just slightly above the transom bottom. Feeling in control now, and slight to moderate trim- in controls any tendency to porpoise. Top speed about 44mph/gps. I'm happy.
Your boat may do fine, though, with less lower unit in the water; giving higher speed,etc. if you want it. Please let us know what you do and how it works for you.
llewellyn posted 02-26-2002 06:34 PM ET (US)     Profile for llewellyn  Send Email to llewellyn     
Forgot to mention, I have a Merc.Laser II prop with 20inch pitch(tried 22 pitch but not enough rpm at WOT)and think it's just right, giving 5400-5500rpm at WOT.
Chesapeake posted 02-26-2002 07:17 PM ET (US)     Profile for Chesapeake  Send Email to Chesapeake     
Hey Chris.......... you shoulda bought the Yamaha.

Sorry, couldn't resist. Good luck. BW

kamml posted 02-26-2002 07:20 PM ET (US)     Profile for kamml  Send Email to kamml     
I just mounted a 2002 90 Merc on my 77 vintage Montauk. This weekend I took some preliminary numbers on Lake Russell. I have a 19" Merc alu. prop and am set at the 1.5" mark on the transom as well. 3000 RPM was good for 26 mph gps, 4000 rpm was good for 32 mph and 4800 was good for 38 mph (all numbers rounded down). Since it was brand new I didn't sustain any speed for more than a minute or two and never exceeded 5000 rpm. I only got up that high momentarily during a trim up on the motor. It porposed when trimmed out too far, otherwise no bad habits what so ever. It planed instantly, and felt down right frisky. At 3000 rpm conversation was at normal volume sitting on the RPS. (yeah I know that would not be a problem with a 4 stroke) Very comfortable motor for the hull. It reminded me of a 66 Corvette I had an opportunity to drive some years ago, the speed was linear with the throttle. I just wish I had more opportunity to run it, I put 35 minutes on it Sunday before the first mate got too cold and her lap dog wouldn't sit still. What a change from the Merc 50. Ken
Landlocked posted 02-26-2002 09:56 PM ET (US)     Profile for Landlocked  Send Email to Landlocked     
BW - I looked at the Yamaha hard but in the end it just came down to economics and getting the most bang for the bucks I had. The merc is a good solid engine with a solid rep and I got it for a price I could swallow - 5,250 with no prop. Yams sure do look nice on the back of a montauk though.

llewellyn - what did that Merc lasor run you? Is it 3 bladed? 44mph in a montauk is flying. I may have to change my name from landlocked to airborn!!!!!

Kamml - we have exactly the same rig. My boat is a 77 (sold in 78) It will be really interesting to compare numbers we get.

Man, I've got the same feeling I had on christmas eve 20 years ago when I knew I was going to get that go-cart I had been asking for the next morning.

whalerron posted 02-26-2002 11:08 PM ET (US)     Profile for whalerron  Send Email to whalerron     

Did you ever calculate your fuel usage with that merc? In your letter, you said you were going to wait until it was broken in before figuring the fuel usage.

Another question. At WOT, is any of your boat in the water or is just the prop submerged?

- Ron

Chesapeake posted 02-27-2002 09:23 AM ET (US)     Profile for Chesapeake  Send Email to Chesapeake     
Chris: Hope you know I was only kidding you. The Merc is a great engine for the Montauk. Sounds like you got yourself a good deal as well. Hope you have a blast with it for a long, long time.

I bought a Yamaha 90 new in 2001 and it was about the same price, but Yamaha seemed to make its margin on the accessories. Binnacle, digital tach, key switch and morse cables added about $625 to the price of the motor, before rigging.

Landlocked posted 02-27-2002 10:31 AM ET (US)     Profile for Landlocked  Send Email to Landlocked     
BW - No problem - that's what I like about this site - great info and enough good natured ribbing to keep you coming back. Nobody says you can't have info and entertainment at the same time.

As far as the prop goes - just got and email from Chuck Bennet at Whaler - He says the factory mounts the Merc 90 with one hole showing and installs a Black Max 12.75 x 21.


Bigshot posted 02-27-2002 01:56 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
You can always raise it more later. You might want to consider a jack plate if not too late.
Landlocked posted 02-27-2002 02:42 PM ET (US)     Profile for Landlocked  Send Email to Landlocked     
Will probably add a Jackplate later. Uncle Sam's refund has been depleated.

Chuck said that with the BW recomended setup I should expect 42mph. I think that will do just fine for now. Beats the heck out fo 31!

Bigshot posted 02-27-2002 03:34 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
What did you have a 25 on that thing:) You will think you hit Mach1, no wonder you are anxious.
Landlocked posted 02-27-2002 03:50 PM ET (US)     Profile for Landlocked  Send Email to Landlocked     
That could be the problem - maby someone just painted 85 on my old cowling - it was a 25 in disguise.

Glad I won't spend this summer working out bugs like last year (remember the motor or prop problem post that went on for ever?) I think I spent about 40 hours and a couple hundred bucks to gain 2 mph!!!

Got a buddy that's thinking about putting my old 85 on a 17' monarch work boat(aluminum)
I think we will both be happy.


Bigshot posted 02-27-2002 03:56 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
She's tired but that don't mean a carb cleaning and a decarb won't do wonders.
Landlocked posted 02-27-2002 04:18 PM ET (US)     Profile for Landlocked  Send Email to Landlocked     
SHhhhh - my wife might hear ya - I've got her convinced the ol' girls on her last leg!

Just kidding. Just too many worries. Want a dependable motor. Its not just me out there anymore got a little girl that doesn't react well to being stranded. Time to put more fun and less stress in our trips.


Bigshot posted 02-28-2002 11:42 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
I hear ya...I traded my 1989 in on a new one.
jimh posted 03-01-2002 09:04 AM ET (US)     Profile for jimh  Send Email to jimh     
[Changed TOPIC. Was "new motor'.--jimh]
Landlocked posted 03-01-2002 10:04 AM ET (US)     Profile for Landlocked  Send Email to Landlocked     
Sorry Jim - Was just trying to keep it short. Will be more concise in future.


Chesapeake posted 03-01-2002 05:38 PM ET (US)     Profile for Chesapeake  Send Email to Chesapeake     
Chris: How does the old saying go -- More truth is said in jest than not? I went through the same thought process this summer. We had a 76 Johnson '85 without tilt / trim. It ran pretty well. But it would take two or three (more?) cranks in the morning to start. Out on the water it might take a couple to restart. Was that kind of situation where you didn't mind running it on a small inland lake, but the thought of taking it out on Lake Michigan was unnerving.

So, the conversation with my wife about how we absolutely needed a new motor was kind ... interesting. Bringing up safety with our 3 and 4 year olds in the boat made the decision pretty easy for both of us to live with.

And it really nice to have a fast boat with power-tilt, isn't it??


Landlocked posted 03-02-2002 12:29 AM ET (US)     Profile for Landlocked  Send Email to Landlocked     
Sounds like we were having the same experiences Bob. The old 85 never left me stranded - just left me out a little longer than planned a time or two. Hard to start, made noises it shouldn't and generally stressed me out everytime we went out. But no more!!! I'm a mercury man now - ha ha.

No wise cracks about the Mercury Blues OK.


Flipper posted 03-02-2002 07:28 AM ET (US)     Profile for Flipper  Send Email to Flipper     
...None from me...congrats!I too, would suggest a jackplate when you get the chance.
llewellyn posted 03-04-2002 09:35 AM ET (US)     Profile for llewellyn  Send Email to llewellyn     
Ll, I took Chuck Bennett's advice too; the engine is mounted 1 hole showing; the bottom tip of the engine will not quite clear the garage floor, but it performs great!The Merc.Laser II is a 3 blade, stainless, 20 pitch. I bought it used for $150. No fuel consumption yet, Ron. If I raise my arms the boat doesn't touch water:-)
alaskadan posted 03-06-2002 04:51 PM ET (US)     Profile for alaskadan  Send Email to alaskadan     
I have a 89 Montauk that I recently repowered with a 90hp Honda. I have not had the boat in the water and hope to do so as soon as the the weather is better to do some tests. I was concerned about the weight of the Honda 9OHP. I spoke to someone at the Boston Whaler factory and was assured that the Honda would be an very good combination.
They sent me an article about some tests which convinced me to go ahead with the Honda. I would like to hear from someone who has actually had some experience with the Montauk and the Honda 90. I am eager to get out there and test it and hope performance is good. We usually ride with only two people.
kamml posted 03-09-2002 05:13 PM ET (US)     Profile for kamml  Send Email to kamml     
Despite the cold front moving in I took the Montauk up to Lake Murray (near Columbia SC) this afternoon. I figured I had a couple of hours in 70+ degree temperatures before the weather moved in. I was able to get about 1.5 more hours on the 90 Merc before it started to get chilly on the water. The conditions were fair to poor because of a strong northwest wind across the lake. Still I managed a short flat out run up to 5200 RPM and 41 mph gps with three people aboard. It gets quite hairy in a stiff chop at that speed so I backed off before it was fully wound out, too much bouncing around for any comfort. But I still have the grin an hour and a half later. I noticed that the prop torque all but goes away with just a little trim up. My last Merc had hydraulic steering so I never noticed the strong torque affect before. Its obvious this boat doesn't have NFB steering controls. Ken
Landlocked posted 03-11-2002 10:06 AM ET (US)     Profile for Landlocked  Send Email to Landlocked     
That's what I want to hear!!! Looking forward to breaking mine in as soon as the Bass Pro Guys finish. Currently experiencing reservations about my choice of shops but I'll withhold comment until I see the finished job.


jhill posted 03-21-2002 03:48 PM ET (US)     Profile for jhill  Send Email to jhill     
I have a 89 Montauk with a 89 Johnson 88hp. I can get 46 mph gps with three to four people. I has power trim. You people aare not living right. A friend with a 2000 model has a 125 Merc and gets 50mph.
Landlocked posted 03-29-2002 09:41 PM ET (US)     Profile for Landlocked  Send Email to Landlocked     
Some preliminary numbers

Took the new motor out for the first time today. Horrible chop and up to 20 mph gusts but couldn't wait any more.

After the mandatory 1 hour under 3500 rpm, ( most in the 2000 range because my wife was complaining about spinal injuries) I got to open it up for a few 2 minute runs and then back to 3/4 Throttle. Downstream, with the wind to my back and going fast enough that the boat was just going across the top of the waves, the ride was bearable.

The boat popped up on plane immediately and the mid-range torque was absolutely incredible. Did not have my GPS out today but my Speedo has always been extremely close to the GPS readings.

Wife child and me in boat & 24gal gas, 42 mph
@ ~ 5000 rpm. Me alone in boat 44mph at 5,200 rpm. This was WOT and trimmed to the brink of control. I could increase RPM's by trimming further but the prop broke lose at the slightest bump and it was definately on the edge of control.

Motor was mounted 2-holes up. Requested 1 but apparently they didn't want to deal with the lower bolt hole problems.


MikeG posted 03-30-2002 12:58 PM ET (US)     Profile for MikeG  Send Email to MikeG     
I am running a 88 Montauk with a '88 88SPL. I'm getting 38mph on the gps with a light load, 36mph with 6 adults. Big difference from 46mph. The engine was just checked over and has good compression on all 4 cyl. I'm adding TnT this week but I have a few questions about your set up...

1) Do you have bottom paint? (I do.)
2) What type of prop are you running? (I have a 17" pitch SS.)
3) Do you think the ability to trim the engine is getting your additional speed? ie: does it really add 8mph?

Thanks for any replies! Mike

kamml posted 03-31-2002 09:18 AM ET (US)     Profile for kamml  Send Email to kamml     
Way to go! Sounds like your motor is running great. Flat out my hull gets a little hairy, chine walking from side to side, bumping around and across the water. Mine too has terrific midrange, it wants get going, and I mean mean get going, anytime I advance the throttle. On my hull 26-28 mph seems to be a good cruising speed. It is quiet enough to talk to the first mate at the lower end and she is is still comfortable at the upper end of this speed. My T&T isn't much good, if I trim out a little it lessens the torque steer, but starts to porpoise if I go to far up. At full throttle it porpoises almost as soon as I dial in any T&T. I went to Hilton Head this weekend and put another 1.4hrs on the engine. After about 3hrs 45 mins total I am only half way through my original 24 gals of premix. Since I added a qt. of Quicksilver to the engine tank I know the VRO is working and fuel use doesn't seem to bad. Great to hear your engine is running so well, Happy Easter. Ken
Landlocked posted 03-31-2002 11:23 PM ET (US)     Profile for Landlocked  Send Email to Landlocked     
Thanks Ken,

28-30 is probably optimal comfort wise on my boat as well and is where we'll spend most of our time. (Nice to be able to cut loose when you want to though, isn't it) Noted Fri. that I could turn 31 at slightly over 4000 rpm. I note 31 just because its the old top speed I could get with the 85 Johnson - and that was Wide out. Like you say, at ~4000 rpm you can carry on a normal conversation at in the RPS. NO way with the old motor.

Long and short, very happy so far. Have about an hour and a half on the motor so far and 6 gallons of gas. That's about twice the range I was getting before.


Landlocked posted 04-01-2002 12:08 AM ET (US)     Profile for Landlocked  Send Email to Landlocked     
One thing I forgot to mention is that I now know the importance of a properly set trim tab.

Fri, after dropping wife and child off at the dock, I went back out for one more run.

Wide out at 44mph, I let go of the steering wheel for just a second. Don't remember why, just let go.

The motor immediately swung hard right and the boat went into an extreme turn. Luckily I was seated and had my left hand on the console rail. I was able to grab the wheel, straighten enough to regain control and reduce throttle. I admit, it was one of the closer calls I've had. I don't spend a lot of time in big water like a lot of you guys but I spend a fair ammount of time pumping 600 - 800 volts of electricity into swift water while trying to avoid rocks and collect fish. What happend Fri scared the crap out of me.

The funny thing is I had noticed some pressure on the wheel that I had never noticed before but it didn't seem to be anything dangerous - just resting my hand on the wheel was enough to counter it. The second I let go though, wham. Those of you getting new motors - watch out until you get that trim tab set.


Salmon Tub posted 04-01-2002 09:56 PM ET (US)     Profile for Salmon Tub  Send Email to Salmon Tub     
It is all about the intake and then about the exhuast. You can always add horsepower, but you got to remember, if you take say a 90 merc, and tweak it up say even 10-15 horses, can all the internals take it. I believe in the mercs, isn't the 115 a different block from the 90? As for the two posts above about the discrepancy in performance between the 88 hp's, one may have a real hot 88, and the other a real cold one. It has everything to do with the most minute adjustments in the carbs, the timing. Engines like to breathe but give it a little to much air, and you will scorch the pistons. I don't trust myself nor any mechanic to mess with that stuff, the few extra MPH or HP are not worth it.
bajabreeze posted 06-14-2002 05:27 AM ET (US)     Profile for bajabreeze  Send Email to bajabreeze     
The 90 and the 115 are the same motor the differnce is the exhaust tube and carb jets. Can it take it, well the bottom end is the same. Give it a try.
bajabreeze posted 06-14-2002 05:32 AM ET (US)     Profile for bajabreeze  Send Email to bajabreeze     
Hey Landlocked, get some hydraulic steering and then you can take your hand off the wheel without becoming a WOOB, Whaler Owner Over Board.

All you guys are touting over 40MPH on GPS with your Whalers, my pathetic 36 MPH (33 Knots) by GPS makes me wonder, what's up with my Montauk? 90HP Mariner, 19P ALum prop. Might be the non whaler custom console, 2 27 series batts and the 34 gallons of fuel?

My friend has a 17ft Montauk as well, we mounted a 140HP Evinrude on it a number of years ago for water skiing and the max we could ever get out of it was 47MPH WOT.

Is the air thinner where you guys are?

Landlocked posted 06-14-2002 10:21 AM ET (US)     Profile for Landlocked  Send Email to Landlocked     
As far as hydraulic steering - its on my wish list - maby next year.

As far as speed, the numbers I have reported have been checked and rechecked and are accurate.

I'm only slightly over 40mph but definately over. I would imagine the difference is in the weight of our respective set-ups. My whaler is completely stock. I only have 1-battery. Maximum fuel load is 24 gallons.


ewalsh posted 06-14-2002 12:51 PM ET (US)     Profile for ewalsh  Send Email to ewalsh     
My father has a 87 17' SS with a 91 Johnson 100GT. No bottom paint. Lake boat. Aluminum prop. With one person, a little fuel and full trim, the boat does 50mph/GPS.

I think it has to do with the driver's seat position being further to stern than the Montauk. Plus the boat has less than 50lbs of gear. And I have heard that the 100GT's are a little HOT.

FISHNFF posted 06-19-2002 12:04 AM ET (US)     Profile for FISHNFF  Send Email to FISHNFF     
I am convinced that the fastest configuration is a Sport/SuperSport with a low console. Less wind resistance and weight. My console mods puts the windshield above eyelevel (very anti-aerodynamic), and the console box adds another 55 lbs. On the Bay today with 12+11 gallons fuel, 2 batteries, 17 gallon livewell, and a scum line from 2 weeks in the water, the WAAS GPS maxed at 35.1 knots turning a 17" Ballistic 5900RPM on a Merc 90 4S. Oh yeah, 6 Stripers(10-16lbs) and a Ling for a 1 hour trip. Loving Life!


kysard posted 06-22-2002 03:14 PM ET (US)     Profile for kysard  Send Email to kysard     
The 90 merc is not the same block as the 115 anymore it is the same as the 75.

Does anyone have fuel conumption data for the 90 merc 2 stroke, it is absent from their website. I know for the 90 yammy is considered fairly fuel efficient would like a comparison between the 2.

jstachowiak posted 06-24-2002 08:38 AM ET (US)     Profile for jstachowiak  Send Email to jstachowiak     
Check out this Mercury website and search the engine you are interested in.
Does not have fuel consumption info.

Ogden Dunes posted 06-28-2002 05:57 AM ET (US)     Profile for Ogden Dunes  Send Email to Ogden Dunes     
I know you are all talking about the 90 merc. I just put on my 17 Super Sport a 100 4 stroke Yamaha. I have put on about 20 hours so I thought it would be a good time check speed on the GPS. I have a Turning Point-express 13.25 diameter 19 inch pitch stainless prop. I am turning 5900 rpm with 450 lbs of breathing meet as passengers ( no not just me!) and 18 gallons of fuel. The speed on my Garmin 3 is 45.4 mph. When I check the Garmin against my two autos it reads 1 mph slower. So I Guess it is running between 44 and 47 mph (light chop). The Yamaha is mounted one inch high on the transom.

I am very happy with the quitness and torque of this new motor although the cost is quite a bit higher. I hope to get more hours out of this unit.

kamml posted 07-06-2002 08:26 PM ET (US)     Profile for kamml  Send Email to kamml     
Landlocked Just got back from vacation today. Yesterday running in to the dock I hit a smooth patch of river and running "uptide" I clocked 39 on gps with 3 on board (550lbs) and 14 gallons left in the tank. That was running my 13x17 prop and maxing it out around 5500. I switched down to the 17 for ocean running and passenger hauling. Needless to say the acceleration is super at most any speed with the 17. On the smooth Colleton River I was able to trim up, take it over the edge, then bring it back for the speed run. Real loud, but lots of fun. I expect my numbers with the 19" will have gone up some now that I have 21 hrs on the motor. Ken

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