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Engine mount
JPB
#1 Print Post
Posted on 04/12/14 - 3:38 PM
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I am mounting an engine with the standard bracket and it will require me to fill the blind holes and drill new holes like has been discussed well on this site before. After looking at all the reference here, I would like to describe my plan and get some feedback to be sure I'm right.

After filling the original blind holes, I will drill the green holes at 6.5 inches below the original top holes. I understand that I should be able to use the original top holes. The top bolts will be mounted through the last of the top holes...(see picture of the bracket on personal page. The bottom bolts will be mounted through the first of the bottom holes. If I measured right this will place the top of the bracket aboutt 1.5 inches higher than the top of the transom? Based on what i read this is desirable?

The boat is a 1982, 17 foot custom and the engine is a 40 mercury two stroke tiller with electric start and power trim. The boat is only outfitted with a wood bench seat across the back, one battery in back, 94 QT cooler in center, and 12 gallon gas tank forward. I was also wondering what prop might be good for this setup?

Thanks in advance. Joey


Edited by JPB on 04/12/14 - 3:50 PM
 
Joe Kriz
#2 Print Post
Posted on 04/12/14 - 4:31 PM
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What year is that 40hp Mercury?

Most newer motors have 4 or 5 bolt holes at the top and slots at the bottom (except Mercury where some have bolt holes also at the bottom instead of slots).
See this photo of a 40hp Yamaha.
http://www.whalercentral.com/images/p..._64/13.jpg

Are you sure 40hp is going to be enough for you?
http://www.whalercentral.com/articles...ticle_id=5

I have seen a pair of 40's on the back but never just one 40hp.
The boat is rated for 100hp max and 35hp min
http://www.whalercentral.com/userphot...lbum_id=14


Edited by Joe Kriz on 04/12/14 - 4:33 PM
 
JPB
#3 Print Post
Posted on 04/12/14 - 5:01 PM
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The mercury is a 1999 two stroke tiller. I thought it was unusual to only have 3 holes on top as well. There are no slots on the bottom...only 3 holes there too. I added another picture of the overall outboard on my personal page.

The 40 horse tiller will be sufficient for our needs.

Thanks


Edited by JPB on 04/12/14 - 5:26 PM
 
Joe Kriz
#4 Print Post
Posted on 04/12/14 - 5:33 PM
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Maybe some of the Mercury experts can give you more info as I am not a Merc Man.

 
gchuba
#5 Print Post
Posted on 04/13/14 - 6:46 AM
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Wouldn't a Jack Plate solve the issue of motor height? Saves from drilling into the transom with a "guess" at best height for the specific motor (only 3 holes of movement). Also, if a repower in the future, adjust the height of the Jack Plate instead of potentially drilling holes over again at the original location. Just my $ .02.
gchuba

 
Tom W Clark
#6 Print Post
Posted on 04/13/14 - 8:20 AM
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Joey -- I think your plan is good.

Yes, the smaller Mercurys only have three set of holes instead of their usual five.

Verify the spacing on the holes in the motor mounting bracket before drilling the transom.



 
Tom W Clark
#7 Print Post
Posted on 04/13/14 - 8:25 AM
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I do not see a jack plate as a very solution to this problem.

- If the transom holes are not BIA standard then the jack plate won't fit them either and the jack plate will need to be drilled

- The jack plate will add considerable expense to the project and may add a delay waiting for it to arrive

- A jack plate will add some setback which is the last thing a tiller steered 40 HP motor on a 16'-7" hull needs.

- A jack plate may offer more vertical adjustment but again, we are talking about a 40 HP tiller steered motor and once the best height is found I do not think it going to need to be readjusted, and three sets of bolts holes ought to be more than enough to find that best height.

 
gchuba
#8 Print Post
Posted on 04/13/14 - 9:18 AM
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Tom, I see your point. I did not think that a 2 1/2 " set back with a smaller jack plate would create leverage issues with the tiller handle. I thought the versatility of the plate wold be an advantage for long term use. I just keep reading about all these fellows at some time or other having issues with "how many holes up?" and having to remove the motor for adjustment.
gchuba

 
Tom W Clark
#9 Print Post
Posted on 04/13/14 - 9:26 AM
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What versatilty does one need once the motor is set?

 
gchuba
#10 Print Post
Posted on 04/13/14 - 9:46 AM
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Tom, along the lines of drilling holes at the incorrect starting height within the motors adjustment limits (did not take into account the body weight of a person at the tiller) or a repower down the road occurs with different engine dimensions. I was also under the impression that the jack plate improves the dynamics of a boat.
gchuba

 
Tom W Clark
#11 Print Post
Posted on 04/13/14 - 9:56 AM
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I don't follow you. If one can't drill holes in the right spot, they probably shouldn't be trying to install a jackplate either. A jackplate won't fix stupid.

Jackplates can have dramatic influence on a boat's handling and speed in some instances on some boats. I do not think a 40 HP tiller steered motor on a 16'-7" Whaler is any sort of high-performance rig that would benefit.

Repowering in the future is one very good reason to get the transom bolt holes on the industry standard BIA lay-out now, so its done with once and for all. Trying to accommodate those old blind holes just delays the inevitable the next time a new motor is installed. That makes no sense to me.

 
gchuba
#12 Print Post
Posted on 04/13/14 - 10:07 AM
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Tom, I did not understand that his approach was BIA standard. I was under the impression that the method "...6.5 inches down..." was random for the motor. I thought that jack plate once mounted, would bring his bolt pattern for the motor up to standard.
gchuba

 
JPB
#13 Print Post
Posted on 04/13/14 - 10:31 AM
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To clear up my original thoughts.

In the OP....I mention it is a standard bracket and I will drill the green holes which are 6.5 inches below the original top holes.

Because this mount only has 3 holes of adjustment and the distance between lowest top hole and the highest bottom hole is 6.5 inches there will be no adjustment with the green holes. I like the idea of drilling the green holes instead of the yellow to avoid the bottom of the splash well. Mounting this engine with the green holes will leave the bracket 1.5 inches above the transom. Of course this would also allow mounting any other standard bracket in the future . I am going with this plan. Thanks guys for the feedback.

I know there are not many choices for this engine but could you recommend a prop for this setup Tom?

 
JPB
#14 Print Post
Posted on 04/19/14 - 5:35 PM
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I got the blind holes filled this week and replaced two of the drain tubes on the transom. I was ready to drill the green holes however the engine looked a little high to me so I took some pictures for some feedback. The last 4 pictures on my personal page shows the engine mounted all the way up.

Picture one: the bracket is about 1.5 inches off the transom.

Picture two: a board laying across the cavitation plate with engine trimmed all the way down.

picture three: motor is trimmed up slightly

picture four: board is in same position as 3 and engine is trimmed all the way down.

My question is will this mounting position work?

Thanks.

Joey

 
dgoodhue
#15 Print Post
Posted on 04/19/14 - 7:41 PM
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In your pictures, it looks fine to me. The water height rises from the back of the transom by the time it gets your motor. You really do not need the yellow holes. I would drill the green holes.


Dave
 
Whalerbob
#16 Print Post
Posted on 04/20/14 - 11:42 AM
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I'm getting ready to do the same job and have read all of the related threads. I'm not sure I understand the bolt pattern of that 40 but the reason I don't want to drill the Red holes (all the way down) is you won't have room for washers inside the splash well and drilling the green holes (all the way up) doesn't leave options if it's too high. I'm planning to drill the yellow holes (middle) and mount 2 holes up. I'll let you know how it goes.

 
Joe Kriz
#17 Print Post
Posted on 04/20/14 - 11:54 AM
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Whalerbob,

Drilling the Green holes will mount standard bracketed motors 2 holes up.

You would not be able to lower the engine less than that but your could go up another hole.

Remember, measure and layout both the inside and outside of the transom holes before drilling anything.

 
tmann45
#18 Print Post
Posted on 04/20/14 - 1:32 PM
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JPB wrote:
Picture two: a board laying across the cavitation plate with engine trimmed all the way down.

picture three: motor is trimmed up slightly

picture four: board is in same position as 3 and engine is trimmed all the way down.

Joey

The usual way to measure ventilation plate height is to have the plate parallel to the bottom of the hull, as it seems to be in picture three.

 
JPB
#19 Print Post
Posted on 04/21/14 - 11:38 AM
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Yes, picture 3 shows the engine trimmed up slightly so that the angle of the ventilation plate is close to the same angle as the bottom of the boat.

How much higher can the ventilation plate be above the bottom of the keel?


Edited by JPB on 04/21/14 - 2:38 PM
 
Finnegan
#20 Print Post
Posted on 04/21/14 - 3:45 PM
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Assuming the 7-1/4" vertical spacing can be accomplished (it's going to be VERY close!), I would use that spacing. It will mount the engine at Whaler's specified height, and should work well with any propeller. This also gives you the option of going up one more hole if needed.

With only 40 HP on that hull, your top end speed is only going to be around 28 MPH. This is not the realm of elevated engine heights are performance props, nor is tiller steering.

With engine only one hole up, and at these speeds, you can use a Mercury's surprisingly good aluminum prop with good results. If you go up one more hole, you may need a more expensive SS prop to avoid ventilation/slippage.

Later and current Mercury 40-60HP engines now have the 5 hole mounting pattern restored.

 
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