1989 Montauk 17, Yamaha 90

Optimizing the performance of Boston Whaler boats
17MontaukHelena
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1989 Montauk 17, Yamaha 90

Postby 17MontaukHelena » Wed Jul 10, 2019 12:05 pm

Hi all, I am reaching out for advice on my boat's performance. Here are the data:

1989 17 Montauk
24-gallons Fuel
One Person- 250-lbs
Two Batteries at Stern
2007 Yamaha 90 two-stroke with 230 Hours, Cylinder pressure 125, 122, 120-PSI
Yamaha 17K propeller painted stainless
Engine mounted in lowest position
Boat has bottom paint
Maximum boat speed is 31-MPH.
Max engine speed is 4700-RPM (Factory spec is 4500-5500)
Empty, at rest the boat floats properly

My buddy's 16 Nauset with an older 70 Yamaha comes right on past me.

Do you all have any suggestions?

Thank you,

Whaler 1.jpg
Fig. 1. The boat under discussion, tied to the dock and seen from astern.
Whaler 1.jpg (125.93 KiB) Viewed 6497 times


Whaler 3.jpg
Fig. 2. The boat under discussion.
Whaler 3.jpg (111.26 KiB) Viewed 6497 times

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Phil T
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Re: Performance Problems 90 Yamaha 89 17 Montauk

Postby Phil T » Wed Jul 10, 2019 12:32 pm

Your engine is not operating properly.

Most likely you are only running on 2 cylinders, not 3.

The expected WOT performance with your setup is 39-43 mph @ 5400 rpm'.
Member since 2003
1992 Outrage 17, 1992 Evinrude 115

17MontaukHelena
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Re: Performance Problems 90 Yamaha 89 17 Montauk

Postby 17MontaukHelena » Wed Jul 10, 2019 12:50 pm

Hi Phil, I have had two reputable mechanics sea trial the boat and both verified normal operation of the outboard. It sounds great at all RPM ranges. Is there anything I can do myself to test the operation of all 3 cylinders?

17MontaukHelena
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Re: Performance Problems 90 Yamaha 89 17 Montauk

Postby 17MontaukHelena » Wed Jul 10, 2019 12:57 pm

I should add that the carbs were rebuilt 2 years ago and the motor preformed the exact same prior to rebuild of the carbs

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Phil T
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Re: Performance Problems 90 Yamaha 89 17 Montauk

Postby Phil T » Wed Jul 10, 2019 1:18 pm

With the engine NOT running - Unplug the top spark plug boot.
Start the engine. Run for a minute. Monitor sound.Shut down.

Reinstall top plug boot. Remove middle boot.
Start engine, Run for a minute. Monitor sound.Shut down.

Reinstall middle plug boot. Remove bottom plug boot.
Start engine, Run for a minute. Monitor sound.Shut down.Reinstall bottom plug boot.
Member since 2003
1992 Outrage 17, 1992 Evinrude 115

17MontaukHelena
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Re: Performance Problems 90 Yamaha 89 17 Montauk

Postby 17MontaukHelena » Wed Jul 10, 2019 1:32 pm

Phil T wrote:With the engine NOT running - Unplug the top spark plug boot.
Start the engine. Run for a minute. Monitor sound.Shut down.

Reinstall top plug boot. Remove middle boot.
Start engine, Run for a minute. Monitor sound.Shut down.

Reinstall middle plug boot. Remove bottom plug boot.
Start engine, Run for a minute. Monitor sound.Shut down.Reinstall bottom plug boot.
'

Phil, can't thank you enough. I will give it a shot and report back tonight or tomorrow. Thanks man!

flymo
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Re: Performance Problems 90 Yamaha 89 17 Montauk

Postby flymo » Wed Jul 10, 2019 1:45 pm

How long have you had the boat? Has it always run this way, or is this a recent problem that has cropped up?

I very much doubt you are running on two cylinders - you'd likely not be able to even get on a plane if that were the case.

Is the bottom in decent shape, or rough and nasty? That can make a lot of difference.

17MontaukHelena
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Re: Performance Problems 90 Yamaha 89 17 Montauk

Postby 17MontaukHelena » Wed Jul 10, 2019 1:51 pm

flymo wrote:How long have you had the boat? Has it always run this way, or is this a recent problem that has cropped up?

I very much doubt you are running on two cylinders - you'd likely not be able to even get on a plane if that were the case.

Is the bottom in decent shape, or rough and nasty? That can make a lot of difference.


I have had the boat for five years and it has always performed exactly the same as now.

The bottom isn't dirty in the respect that it never stays in the water.

At some point in its life, however, it had an owner that LOVED adding bottom paint. Lots of coats on her and its not in good shape. It has been recommended to me to have the paint removed and bottom gel-coated.

I am not sure who in Maryland would do that for me.

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Phil T
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Re: Performance Problems 90 Yamaha 89 17 Montauk

Postby Phil T » Wed Jul 10, 2019 3:01 pm

Really bad bottom paint will only reduce speed by 3-4 mph.
Member since 2003
1992 Outrage 17, 1992 Evinrude 115

jimh
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Re: 1989 Montauk 17, Yamaha 90

Postby jimh » Wed Jul 10, 2019 5:42 pm

As seen in Fig.1. the battery is on Port. Move the battery to Starboard. Propeller torque tends to make the boat lean to Port, and having the battery on Port increases that tendency.

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Phil T
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Re: 1989 Montauk 17, Yamaha 90

Postby Phil T » Wed Jul 10, 2019 5:54 pm

Just for the record.

Owners with this model and engine combination recommend these props. Engine mounted 2 holes up.

13" x 17" Yamaha Painted Stainless Steel ***
13-1/4" x 16" Yamaha Performance Series Three Blade
13-1/4" x 15" Turbo 1 4.25

***OP reports this is his prop.
Member since 2003
1992 Outrage 17, 1992 Evinrude 115

17MontaukHelena
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Re: 1989 Montauk 17, Yamaha 90

Postby 17MontaukHelena » Wed Jul 10, 2019 6:15 pm

jimh wrote:As seen in Fig.1. the battery is on Port. Move the battery to Starboard. Propeller torque tends to make the boat lean to Port, and having the battery on Port increases that tendency.


There are two batteries. One on the port and one on the starboard side

17MontaukHelena
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Re: 1989 Montauk 17, Yamaha 90

Postby 17MontaukHelena » Wed Jul 10, 2019 6:17 pm

Phil T wrote:Just for the record.

Owners with this model and engine combination recommend these props. Engine mounted 2 holes up.

13" x 17" Yamaha Painted Stainless Steel ***
13-1/4" x 16" Yamaha Performance Series Three Blade
13-1/4" x 15" Turbo 1 4.25

***OP reports this is his prop.


Phil, do you think either of the two props listed below the one I have would help me out?

17MontaukHelena
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Re: Performance Problems 90 Yamaha 89 17 Montauk

Postby 17MontaukHelena » Wed Jul 10, 2019 8:20 pm

Phil T wrote:With the engine NOT running - Unplug the top spark plug boot.
Start the engine. Run for a minute. Monitor sound.Shut down.

Reinstall top plug boot. Remove middle boot.
Start engine, Run for a minute. Monitor sound.Shut down.

Reinstall middle plug boot. Remove bottom plug boot.
Start engine, Run for a minute. Monitor sound.Shut down.Reinstall bottom plug boot.


Hi Phil, I did the test and it sounded the same on each plug I tested

flymo
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Re: 1989 Montauk 17, Yamaha 90

Postby flymo » Wed Jul 10, 2019 9:03 pm

So you have two things that clearly need fixing, those being the rough bottom paint and the motor mounting height. You are running a prop that others have had good luck with, so that's not the concern. It's hard for me to see that the mounting height and rough bottom could account for losing that amount of speed, but still you might as well fix what's broken, before looking at other things.

Any capable marina should be able to soda blast and redo your bottom paint - no need to have it re-gelcoated. Likewise, any capable marina should be able to raise the motor two holes, although if it's mounted using the blind holes, as many of this vintage were, it's a bit more work. I would recommend getting that work done, and seeing where you stand afterwards. Both of those fixes will make your boating experience more fun, so no matter what they are worth doing.

A couple more things, and excuse me if you know these already:

1) you will need to trim the motor out to achieve top speed - this is extra important with your motor mounted low.
2) if your prop is banged up, it can make a lot of difference.

17MontaukHelena
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Re: 1989 Montauk 17, Yamaha 90

Postby 17MontaukHelena » Wed Jul 10, 2019 9:07 pm

flymo wrote:So you have two things that clearly need fixing, those being the rough bottom paint and the motor mounting height. You are running a prop that others have had good luck with, so that's not the concern. It's hard for me to see that the mounting height and rough bottom could account for losing that amount of speed, but still you might as well fix what's broken, before looking at other things.

Any capable marina should be able to soda blast and redo your bottom paint - no need to have it re-gelcoated. Likewise, any capable marina should be able to raise the motor two holes, although if it's mounted using the blind holes, as many of this vintage were, it's a bit more work. I would recommend getting that work done, and seeing where you stand afterwards. Both of those fixes will make your boating experience more fun, so no matter what they are worth doing.

A couple more things, and excuse me if you know these already:

1) you will need to trim the motor out to achieve top speed - this is extra important with your motor mounted low.
2) if your prop is banged up, it can make a lot of difference.


Thank you for taking your time for the lengthy response! Do you think I need to hire someone to raise the motor up or can I do it myself with one other person? Are you thinking 3 rd hole down from the top?

Prop is in perfect shape and yes that rpm and speed is with playing with the trim

flymo
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Re: 1989 Montauk 17, Yamaha 90

Postby flymo » Wed Jul 10, 2019 9:50 pm

Whether you can raise the motor yourself depends on how handy you are, and whether your motor was mounted using the blind holes. If the latter, you'll need to do some filling and drilling. The are some good articles and info here on the subject.

There's no reason you can't clean up the bottom paint yourself either, with sandpaper and some time. It's a nasty, dirty job but it's not rocket science.

That all said, since your prop is OK and you've been working the trim, it does seem like something else is wrong. One simple check is to take the air box off and make sure the carb butterflies are opening all the way at WOT - check with the engine off, of course. If they are not opening you may want to do a "link and sync" on the carbs and linkages. You can do this yourself with the factory manual, or have a mechanic tackle it.

jimh
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Re: 1989 Montauk 17, Yamaha 90

Postby jimh » Thu Jul 11, 2019 7:17 am

Check the spark plug wires. The rubber boot on the plug wire may not be making good contact with the spark plug electrode. I owned some 1987 Yamaha three-cylinder engines. I had to use a nylon cable tie to increase tension of the rubber spark plug boot to hold it in place on the spark plug electrode.

When the three-cylinder engine was running on only two-cylinders due to a loose plug wire, the boat would have extreme difficulty getting on plane.

17MontaukHelena
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Re: 1989 Montauk 17, Yamaha 90

Postby 17MontaukHelena » Thu Jul 11, 2019 7:44 am

jimh wrote:Check the spark plug wires. The rubber boot on the plug wire may not be making good contact with the spark plug electrode. I owned some 1987 Yamaha three-cylinder engines. I had to use a nylon cable tie to increase tension of the rubber spark plug boot to hold it in place on the spark plug electrode.

When the three-cylinder engine was running on only two-cylinders due to a loose plug wire, the boat would have extreme difficulty getting on plane.


Thanks Jim, plug wires are new. The motor performs great and pushes the boat fine even with 7 people on board. It pops right up getting on plane, it will almost throw you if you aren’t holding on.

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Re: 1989 Montauk 17, Yamaha 90

Postby jimh » Fri Jul 12, 2019 9:47 am

What is the elevation of the lake?

17MontaukHelena
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Re: 1989 Montauk 17, Yamaha 90

Postby 17MontaukHelena » Fri Jul 12, 2019 10:33 pm

jimh wrote:What is the elevation of the lake?


Sea level, this is on the Chesapeake and it’s tidal

biggiefl
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Re: 1989 Montauk 17, Yamaha 90

Postby biggiefl » Mon Jul 15, 2019 12:31 pm

I had the same setup and you are missing 10mph and 7-800rpms. First thing I would do is check the throttle and make sure you are getting full throttle. Compression is within 10% and prop is a good fit for that boat. Easy to do. Pull cowl, put throttle to full and then remove the cable at engine and see how much more you can get with it removed. I have seen people not have the full range of the throttle before, I don't think you have an engine problem and bottom paint would not effect that much of a loss, maybe 1-3mph.

As far as raising engine, it depends if in the blind holes. Take a pic of the transom, inside the well and outside so we can see the setup. Many used this mounting as it was customary to have the engine smack down on the transom which has since been overturned as necessary and is just the opposite.
On my 24th Whaler. Currently in the stable: 86 18' Outrage, 81 13' Sport(original owner), 87 11' Sport, 69 Squall. :roll: