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Author Topic:   Feelin' the NEED for SPEED!
Landlocked posted 09-06-2000 11:20 PM ET (US)   Profile for Landlocked   Send Email to Landlocked  
What speed should I reasonably be able to obtain with 78 Montauk/ 79 Johnson 85hp (low profile, V4) Combo...

Right now alone in the boat with top down, on smooth water, and wind at my back, I can get 31mph (gps). With 3 other guys and a cooler full of cool-aid and oreos, I get 25mph. (usually cruise at ~20) at somewhere less than WOT. I'm not sure of the pitch of my prop - not stamped on outside and I havent taken it off yet. Also, don't have tach yet, looking for one to match my speedometer...

Is this about as good as I should expect, or should I start the process of trying out different props....

Quick take off isn't really my bag, just want more speed for those loooong river trips.


triblet posted 09-07-2000 02:02 AM ET (US)     Profile for triblet  Send Email to triblet     
My '98 Montauk with Evinrude 90 and 17"
prop will do 36 knots (41 MPH) (DGPS) on flat
water with just me in it. I hear tales
of faster Montauks.

Get a tach before you start messing with
props, and pull the one you've got to see
what it is (you should pull it and regrease
the splines yearly anyway).

Chuck Tribolet

Lil Whaler Lover posted 09-07-2000 07:30 AM ET (US)     Profile for Lil Whaler Lover  Send Email to Lil Whaler Lover     
If the speeds you are posting are accurate I would check a couple of things on the engine before I invested money in a tach or a prop. The speeds are way off for a 85 and a little off of what is reasonable for a 50 HP. Therefore I would recommend a compression test and a carb cleaning before re-propping. No sense spending good money on an engine that may have other problems. Should you choose to re-prop first, a 17" pitch usually gives the best overall performance with an OMC 85 but a strong 85 will pull a 19" pitch adequately. Most importantly DO NOT EXCEED 5,500 rpm's with this engine.
When you do get the prop off let us know what size it is. If you cannot read the numbers on it try some carb cleaner and a wire brush where the numbers are and they often will become readable again. If you only get the prop number not the diameter and pitch, list the number it can be looked up. Dave
bigz posted 09-07-2000 07:48 AM ET (US)     Profile for bigz    
Chris -- I heartily endorse Dave's suggestion get the engine checked out first and foremost -- if she is pulling extremely low compression then a new prop ain't going to help ---
I might add this should be the first step anyone takes if they feel there boat/engine is not performing to specs --- Tom
Landlocked posted 09-07-2000 03:31 PM ET (US)     Profile for Landlocked  Send Email to Landlocked     
Thanks guys, I'll take the prop off and check it tonight. The speeds are accurate, I have a Magellan Map 410 GPS that is dead on with the truck speedometer. It is also giving me within 1 - 2 MPH of what the boat speedometer is reading.

The only engine symptoms I have noticed is that it is very hard to get started when cold, have to pump the bulb several times during the process of starting it and choke the be-dicksons' out of it. Once warm, however; it runs fine and starts fine.

I'll post more info when I get it...


Landlocked posted 09-07-2000 03:34 PM ET (US)     Profile for Landlocked  Send Email to Landlocked     
One more thing, you got my wheels turning. Are you suggesting that I may be looking at a ring job, or a whole new power head? If its the latter, will one of you tell my wife.

Lil Whaler Lover posted 09-07-2000 05:02 PM ET (US)     Profile for Lil Whaler Lover  Send Email to Lil Whaler Lover     

Ain't suggesting any such thing, just that you need to have the condition of the engine evaluated based on your reported performance levels, and then you will be able to make an informed decision about your 21 year old engine.

One other question is how much gear do you have aboard? Are you carrying literally hundreds of pounds of weight that could be removed? Is there any chance that you have absorbed water into the foam? Extra weight is the greatest performance killer of all.

Your description of starting the darn thing could indicate poor fuel supply to the carbs or dirty carbs that I mentioned in an earlier post. I would check the fuel pickups in the tanks, the fuel filter at the fuel pump and consider replacing the fuel pump if the compression test is good. If the compression test shows a bad cylinder or 2, get it to a OMC certified service tech for an estimate. Good luck, Dave

lhg posted 09-07-2000 05:17 PM ET (US)     Profile for lhg    
I would agree with the consensus here. Even an older powerhead rated 85 should do better than 31 on a Montauk. A friend with an old 1975 Merc 70 could do about 36, and another with a powerhead rated Merc 90 in-line 6 could get about 46/47 out of it. Something's wrong! Whaler's 1978 catalog shows speed for your boat/engine combination at 38mph.
Peter posted 09-07-2000 07:24 PM ET (US)     Profile for Peter  Send Email to Peter     
I also agree with the observations and advice here. Just another benchmark. A few years ago a 17 GLS with an 88 SPL was estimated to be about 1 to 2 mph slower than my 18 with 150 Johnson. As configured back then, my 18 would do an easy 48, thus putting the 17 GLS in the 46-47 range.
whalernut posted 09-07-2000 08:25 PM ET (US)     Profile for whalernut  Send Email to whalernut     
Chris, I have a 73` `16 Currituck with a 75` 85h.p. Johnson, this boat screams with a 19in. prop, I may try the 17incher though. My engine just needed a power pack, but at 25 years old and the parts are all original, it is a screamer, all freshwater used. I haven`t a clue to how fast the boat goes, but I`m guessing 45-50 mph. Mind you my boat ways about 300-400 lbs. lighter than you`re Montauk. Eventually, I will switch to a 50-60 h.p. 4-stroker. Regards-Jack Graner.
Landlocked posted 09-07-2000 09:14 PM ET (US)     Profile for Landlocked  Send Email to Landlocked     
To the wife's chagrin, I am sitting in the Kitchen with Prop in hand. I can find no numbers on the inside. On the outside I have found the following:

o 209
721 11U

The guy I bought the boat from a couple of months ago, was religious about taking care of it cosmetically. Hull and deck or sound with the exception of a few spider cracks. The boat was always on a hydrolift in a covered boat house; so I have no reason to believe that there is water in the hull.

He saved every reciept since 1980. (spent more on the top than I did on my first boat)

The things he took it to a dealer for amaze me. "fabricate wood blocks for cooler". On the other hand, He seems to have not noticed mechanical things , though he took it in every year for a tune up and new lower unit fluid.

The trim/tilt will work when not under way but with pressure on the motor, it won't tilt. He said it had always been that way. (I added fluid with-out results, must be a leak)

When I got it, it had just enough reverse to be dangerous, I made adjustments recomended by dave and now have plenty of reverse...

It is entirely possible that something is just out of whack with the tuning. If you guys don't see anything wrong with the prop, I'll eat my pride and take it to a real mechanic. I re-built the engine in my bronco myself. These boat motors just don't make sense.


Landlocked posted 09-07-2000 09:51 PM ET (US)     Profile for Landlocked  Send Email to Landlocked     
A little more info.... I got a "spare prop"
with the boat. The seller said it was the original prop. It appears to be the same size as what's on it now. Imbossed in the hub are 13 x 19 and 382 765.


Lil Whaler Lover posted 09-07-2000 10:00 PM ET (US)     Profile for Lil Whaler Lover  Send Email to Lil Whaler Lover     
These numbers off your prop do not lead me to believe that it is a OMC or Michigan prop. Assuming it is aluminum, the only company I have seen that might have some numbers like those is an outfit called Propco. I have no information on them so I am not able to translate.

What I would expect is that some of the stamped numbers are rebuilders codes. It sounds like the prop may have been rebuilt more than once.

As far at the trim'n'tilt goes. It is probably more difficult to properly rebuild than the engine. My mechanic last summer literally required a sterile field for rebuilding a trim'n'tilt unit as even a small bit of dust could cause it to not hold its position. The normal test is to leave the motor tilted up and measure the leakdown time for it to untilt.

Chris, it sounds like you just need to get an estimate from a dealer you feel you can trust and you will know what it takes to make your engine as nice as your boat sounds.

One more thought. Thanks for letting me know that you were able to adjust your throttle setting to achieve more power in reverse, BUT the question is did you lose any throttle advance when in forward gear??? Did the performance change any after the adjustment???

ALso one more question: does the engine seem to be revving up well (really need the tach to know)? If so could you have a spun hub on the prop that limits performance.

Keep us posted, Dave

Lil Whaler Lover posted 09-07-2000 10:03 PM ET (US)     Profile for Lil Whaler Lover  Send Email to Lil Whaler Lover     

Just got your 9:51 post. That is an OMC prop number and size. Try it and see if your performance changes. That is truly the simplest first step and may answer some of the questions that have been asked. The boat should pull a 19" pitch if the engine is running well. Dave

Landlocked posted 09-07-2000 10:29 PM ET (US)     Profile for Landlocked  Send Email to Landlocked     
Thanks dave,

No loss of performance after making the shifter adjustments. I moved a key switch that was obstructing forward motion and got back the play I lost by moving splines forward.

The un-identifiable prop is indeed aluminum.
I'll switch to the spare and see if anything changes this weekend.

One note, I have always preferred alluminum props because of the amount of debris in water around here. I'd rather break a prop than a lower unit. any thoughts?


Landlocked posted 09-07-2000 10:38 PM ET (US)     Profile for Landlocked  Send Email to Landlocked     
forgot to answer the revving up question...

It revs up to a nice high hum but has never sounded quite like the Johnson 140 I have on my 72 Outrage. the 140 is definately a higher pitch sound. I attributed that to the difference in Hp.

I will get a Tach as soon as possible. I know hum isnt exactly a technical term you can make a judgment on.


reeltime2 posted 09-08-2000 09:15 AM ET (US)     Profile for reeltime2  Send Email to reeltime2     
All this talk about Shifter adjustment got me thinking. Have you checked to make sure your carbs are in the full open position when tour throttle is at w.o.t.
Just a thought,
Landlocked posted 09-08-2000 09:38 AM ET (US)     Profile for Landlocked  Send Email to Landlocked     

I have not. I'll take a look at that tonight. Frankly wasn't even sure I had a problem until I got to talking to you guys. My 140 runs about 47 mph wide open. I figured 31 out of the 85 on my new boat was doing ok. That is until I made an 80 mile round triper on the Tennessee River this weekend. Long ride.

By the way, That trip took 30 gallons of gas. Does that sound like normal fuel consumption? Just looking for problems I might be able to Identify that could account for the slow speed.

bschmitt posted 09-10-2000 09:29 PM ET (US)     Profile for bschmitt  Send Email to bschmitt     
Ahm ... seeinmg that this ist a '78 vintage.
I recently bought a '82 Montauk witn an '82 Johnson.

Did 20knt when I got it. Zzzzzz. Motor fine, hat it checked.

But: The thing has no power trim. So I started playing with the (manual) trim and got 30knt at WOT.

Landlocked posted 09-10-2000 09:50 PM ET (US)     Profile for Landlocked  Send Email to Landlocked     
I have power trim, though not working properly. I raised it to the next notch manually and got too much cavitation.

At the current setting, motor top is parallel with water wide out... I think trim is about right, problem must be elsewhere.

bschmitt posted 09-11-2000 11:06 AM ET (US)     Profile for bschmitt  Send Email to bschmitt     
>I think trim is about right, problem must be elsewhere.<

Well, in that case, and if you are weirded out by outboard engines (me 2 ... I looked for the ignition coil on my '82 Johnson V4 and found several possibles ..), I would find myself a good engine doc and let himself have a look at it. They usually also have a set of spare propellers. I'd look for a trustworthy independent guy and ask him 2 questions:

1.) Is the engine worth the additional work or should it be put out of its misery?

2.) If in the affirmative, how do I get the maxmimum top speed possible, and how much will it cost?

Landlocked posted 10-17-2000 08:43 PM ET (US)     Profile for Landlocked  Send Email to Landlocked     

I finally had time to look at the carbs this weekend. If you look on the side of the motor where the cable linkage connects with the throttle body - there is a Peg at wide open. The butterfly valves can't be opened past this point.

Right now with my shifter at full out - I'm only about 7/8 of the way to this peg. Another words. At full throttle - The butterfly valves are not completely perpendicular to their closed position.

There are three notches on the bracket at the linkage adjustment. 1 (the center one) says "start". One - I believe to be Idle. The third I'm not sure about... Is it WOT. If so, I'm way past that when lever is in full even though valves are not completely perpendicular.

I adjusted the cable to allow the throttle to open all the way to the stop but that messed up my idle so I put it back.

Any suggestions.


reeltime2 posted 10-18-2000 08:26 AM ET (US)     Profile for reeltime2  Send Email to reeltime2     
I have to say im a little confused about the pegs & notches you discribe. But I do know if you dont have the butterfly valves in a full open position when you are at full throttle you are not getting full horsepower. You said when you adj. the cable to get WOT it messed up you idle make sure yor valves are fully closed in nutral and fully open at WOT.
Good luck W/ it,

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