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Mounting height of outboard
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| Berger |
Posted on 04/24/15 - 8:49 PM
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Hi All I'm installing a Merc. Bigfoot 60HP on my 15 Sport and would like to know what the best height is. I have in on the 4th hole and it's at 1/4" below the the bottom of the cavitation plate. Is this right?
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| Berger |
Posted on 04/24/15 - 9:27 PM
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Correction: mounting on the 4th hole leaves the cavitation plate 1/4'" below the bottom of the hull.
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| wlagarde |
Posted on 04/25/15 - 4:22 AM
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Sounds like you have it mounted all the way down. I would mount it as high as possible while avoiding aeration - at least 2 holes up and possibly 3 holes up. See here: http://www.whalercentral.com/articles...cle_id=106
1976 Sport 15 w/ 2005 50hp Nissan 2 stroke |
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| Berger |
Posted on 04/25/15 - 6:45 AM
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So are you saying it needs to go higher? as I mentioned it is on the 4th hole and the cavitation plate is 1/4" below the keel.
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| wlagarde |
Posted on 04/25/15 - 7:00 AM
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Are the mounting bolts passing through the most lower hole in the engine mount? If so the engine is mounted all the way down. Do you have a 20" shaft engine?
2-3 holes up would not usually result in the cavitation plate being BELOW the level of the keel. Mounted 2-3 holes up usually results in the cavitation plate being 1-2 inches ABOVE the level of the keel.
1976 Sport 15 w/ 2005 50hp Nissan 2 stroke |
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| Berger |
Posted on 04/25/15 - 7:17 AM
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So where should the cavitation be, even, high or low of the keel?
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| wlagarde |
Posted on 04/25/15 - 7:35 AM
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wlagarde wrote:
Are the mounting bolts passing through the most lower hole in the engine mount? If so the engine is mounted all the way down. Do you have a 20" shaft engine?
2-3 holes up would not usually result in the cavitation plate being BELOW the level of the keel. Mounted 2-3 holes up usually results in the cavitation plate being 1-2 inches ABOVE the level of the keel.
1976 Sport 15 w/ 2005 50hp Nissan 2 stroke |
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| Joe Kriz |
Posted on 04/25/15 - 10:16 AM
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Berger wrote:
Correction: mounting on the 4th hole leaves the cavitation plate 1/4'" below the bottom of the hull.
That doesn't give us enough information.
4th hole from the top or 4th hole from the bottom?
All the way up or all the way down?
Huge difference.
That is why wlagarde gave you this link so everyone is talking the same language.
http://www.whalercentral.com/articles...cle_id=106
Let us know where your motor is mounted according to the link above.
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| wlagarde |
Posted on 04/25/15 - 10:27 AM
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wlagarde wrote:
Are the mounting bolts passing through the most UPPER hole in the engine mount? If so the engine is mounted all the way down. Do you have a 20" shaft engine?
2-3 holes up would not usually result in the cavitation plate being BELOW the level of the keel. Mounted 2-3 holes up usually results in the cavitation plate being 1-2 inches ABOVE the level of the keel.
Also see correction in bold above.
1976 Sport 15 w/ 2005 50hp Nissan 2 stroke |
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| Berger |
Posted on 04/25/15 - 2:14 PM
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The motor is mounted on the 4th hole from the top. This is a Mercury and there are 5 holes.
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| wlagarde |
Posted on 04/25/15 - 2:24 PM
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OK - So you are 3 holes up. I am surprised the anti-ventillation plate is below the level of the keel. Can you confirm your engine has a 20" shaft?: http://www.whalercentral.com/faq.php?...p?cat_id=7
Pictures if available would also help.
Joe and others may also be able to provide some insight.
Edited by wlagarde on 04/25/15 - 2:25 PM
1976 Sport 15 w/ 2005 50hp Nissan 2 stroke |
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| Berger |
Posted on 04/25/15 - 2:30 PM
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Yes 20" shaft 3 holes exposed above the mounting bolts, cavitation plate 1/4" below the keel.
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| wlagarde |
Posted on 04/25/15 - 2:34 PM
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Alright can you post pictures? What prop do you have (stainless?, pitch?) and have you trialed your setup as described? Hole shot characteristics? Top speed via GPS (I would expect around 40+mph depending upon load if optimized)?
Edited by wlagarde on 04/25/15 - 2:44 PM
1976 Sport 15 w/ 2005 50hp Nissan 2 stroke |
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| Berger |
Posted on 04/25/15 - 4:18 PM
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I can take pictures tomorrow and check the pitch and prop. No I have not trialed this setup. I just bought the engine and am trying to figure out the base height and make adjustments after.
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| Derwd24 |
Posted on 04/25/15 - 7:04 PM
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A better indicator of correct height is the relation of the AV plate to the top of the water when trimmed normally and running on a plane:
http://www.veradoclub.com/index.php?t...opic=137.0
Dave - 1983 Outrage 22 |
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| huckelberry145 |
Posted on 04/25/15 - 10:03 PM
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You will find the top two holes are going to be the only ones needed on the 15' classic hull with modern outboards and propellers. My setup in particular likes three holes up. It seems to handle and bite the water better when cornering at that height. I will add though that my interior furniture and rigging in my "Striper" is probably way different than your Sport and you will find four holes up affording you the better handling and speed/fuel economy setup. Have fun experimenting with it and keep us posted on your results.
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| wlagarde |
Posted on 04/26/15 - 5:19 AM
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huckelberry145 wrote:
You will find the top two holes are going to be the only ones needed on the 15' classic hull with modern outboards and propellers. My setup in particular likes three holes up. It seems to handle and bite the water better when cornering at that height. I will add though that my interior furniture and rigging in my "Striper" is probably way different than your Sport and you will find four holes up affording you the better handling and speed/fuel economy setup. Have fun experimenting with it and keep us posted on your results.
Yes - I believe on your mercury 3-4 holes up will be equivalent to 2-3 holes up on other outboards. Those with a mercury please correct me if I'm wrong.
1976 Sport 15 w/ 2005 50hp Nissan 2 stroke |
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| Berger |
Posted on 04/26/15 - 1:14 PM
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Hi Wlagarde I can't figure out how to post pictures here so I emailed them to you. The prop is 13.75x15 aluminum.
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| wlagarde |
Posted on 04/26/15 - 1:32 PM
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Brian you are 1 hole from all the way up and it looks like you are the equivalent to 2 holes up on a non-mercury outboard. I would trial your set up as is and determine the current WOT RPM and MPH using a tach and GPS. Alternatively, you could raise it all the way up and trial there and lower it if you have aeration. Also bring a second person with you who can observe the water flow across the engine as Derwd24 mentions above. I would also use longer engine mounting bolts and stop nuts.
Also, see here about engine mounting and blind holes: http://www.whalercentral.com/articles...icle_id=82.
...and here for what I did as another reference: http://www.whalercentral.com/userphot...lbum_id=64
What year and model is your mercury? We need to know to determine the lower unit gear ratio which will allow us to use the slip calculator here http://www.mercuryracing.com/prop-sli...alculator/ to help size your prop.
1976 Sport 15 w/ 2005 50hp Nissan 2 stroke |
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| Berger |
Posted on 06/17/15 - 7:45 AM
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OK I have splashed the boat and it runs great! I like the engine height but would like more speed. 1978 Sport with 2003 60HP Merc Bigfoot turning a 13,3/4x 15 aluminum prop. Jumps up on plane and at WOT 6000 she tops out at 33Kts. What size prop should I be looking for?
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