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Performance Advice Needed 17 Montauk 90 Yamaha
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| 17whalerhelena |
Posted on 07/10/19 - 10:05 AM
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Joined: 07/10/19
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Hi all, I am reaching out & looking for some advice on my numbers on my boat. Here is the info below.
1989 17 Montauk
24 Gallons Fuel
1 Person- 250 lbs
2 Batteries at Stern
90 Yamaha 2 Stroke (2007)- 230 Hours- Compression 125, 122, & 120
Factory 17k Propeller (Painted Stainless)
Mounted all the way down (top hole)
Boat is bottom painted
Max Speed is 31 MPH.
Max RPM is 4700 (Factory spec is 4500-5500)
Empty, the boat floats properly
My buddy's 16 Nauset with an older 70 Yamaha comes right on past me.
The carbs were rebuilt 2 years ago & I have had (2) mechanics run the boat and tell me its running within spec.
Do you all have any suggestions?'
Thank you,
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| Blackduck |
Posted on 07/10/19 - 2:19 PM
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Two quick points. Boat should be doing 42 mph, or so. Prop is wrong, you should be running at 5500 rpm. Too much pitch. Try a different prop with less pitch and performance will improve.
Walter Reynolds
1973 Boston Whaler 16 Nauset 90 HP Yamaha |
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| Phil T |
Posted on 07/10/19 - 2:52 PM
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Walt is right on the RPM's but I don't think it's the prop.
Here is a list of the recommended props for the Montauk with the Yamaha 90 2-stroke that members have tested.
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
Raise the engine so the top bolts are in the 3rd hole from the top.
Top
0
0
0 <---- top bolt in this hole.
0
I think that it may be the engine is not running right. Dropping a cylinder or bad powerpack?
1992 Outrage 17 I
2019 E-TEC 90, Viper 17 2+
2018 Load Rite Elite 18280096VT |
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| 17whalerhelena |
Posted on 07/10/19 - 3:11 PM
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Blackduck wrote:
Two quick points. Boat should be doing 42 mph, or so. Prop is wrong, you should be running at 5500 rpm. Too much pitch. Try a different prop with less pitch and performance will improve.
I too agree I would like to see more RPM out of it. If I reduce pitch however (currently at 17) I will increase rpm and drop even more speed. Right?
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| 17whalerhelena |
Posted on 07/10/19 - 3:13 PM
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Posts: 4
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Joined: 07/10/19
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Phil T wrote:
Walt is right on the RPM's but I don't think it's the prop.
Here is a list of the recommended props for the Montauk with the Yamaha 90 2-stroke that members have tested.
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
Raise the engine so the top bolts are in the 3rd hole from the top.
Top
0
0
0 <---- top bolt in this hole.
0
I think that it may be the engine is not running right. Dropping a cylinder or bad powerpack?
I will try changing the mounting of the outboard as you suggest. I had two mechanics run the boat and they said it is operating correctly (spec is 4500-5500)
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| 17whalerhelena |
Posted on 07/10/19 - 5:37 PM
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Member
Posts: 4
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Joined: 07/10/19
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Phil T wrote:
Walt is right on the RPM's but I don't think it's the prop.
Here is a list of the recommended props for the Montauk with the Yamaha 90 2-stroke that members have tested.
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
Raise the engine so the top bolts are in the 3rd hole from the top.
Top
0
0
0 <---- top bolt in this hole.
0
I think that it may be the engine is not running right. Dropping a cylinder or bad powerpack?
I did the cylinder test tonight removing each plug and listening. They all sound the same. How can I tell if it’s the power pack? My current prop is the first one you listed. If I reduce pitch I will gain rpm and lose speed. If I increase pitch I’ll lose rpm and gain speed but at 4700 rpm I don’t have any to lose at this point
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| Walt Krafft |
Posted on 07/10/19 - 6:21 PM
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Change one thing at a time. Raise the motor and retest before messing with the prop.
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| Blackduck |
Posted on 07/12/19 - 7:36 AM
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Well yes, probably isn't just the prop. If you could gain 1 mph per 200 rpm, you would be at only 35 mph, on the optimistic end. So, either the motor is not making 90 hp ,or the boat weighs a whole lot.
Walter Reynolds
1973 Boston Whaler 16 Nauset 90 HP Yamaha |
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| biggiefl |
Posted on 07/16/19 - 10:22 AM
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Posts: 890
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Just like on the wave....put throttle at full and make sure you are getting 100% throttle. Very easy to mess up or have a bad cable that is limiting the range.
PS if that is good, check timing advance.
Edited by biggiefl on 07/16/19 - 10:23 AM
24 Whalers so far.... |
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