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Blind hole mount blues (pics added)
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| Mr T |
Posted on 10/07/09 - 10:10 PM
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Decided tonight was the night to raise my motor (1990 88SPL Evinrude) on the Nauset.
Got a plug cutter for the holes, some epoxy for the plugs, printed up the diagram from here, bolts, drills, vodka, all the stuff needed.
Mounted a hook in the garage and hung a strap on it around the motor. Dropped the trailer tongue all the way down then snugged up the strap; blocks of wood under the skeg holding it in place. Crack the bolts; all good except for one blind hole bolt. Not coming loose, finally had to go borrow a breaker bar and impact socket from the neighbor. Starting to think about the vodka, but no, not yet. Get the motor loose, well that explains it. The bottom blind hole on the motor mount is rusted pretty good and the bolt looks like it’s getting eaten up.
So on with the pattern, line everything up, and decide to drill a small pilot to see where this comes out, because it looks like it is going to be VERY close. Turns out, it’s too close. The hole comes out in the curve of the splashwell. I made sure I went in at 90 degrees to the transom, but this is not going to work. I go back, recheck everything, the pattern and the bolt holes all line up right but it is clear that at 7 ¼ inches the holes will come out in the bottom of the well.
Ended up not being sure how high it could so I chickened out and drilled two more blind holes and mounted the motor two holes up. Hope it works.
Oh yeah never did get to that vodka….
Edited by Mr T on 10/10/09 - 7:47 AM |
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| Joe Kriz |
Posted on 10/07/09 - 10:28 PM
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Hi T,
How far down on the transom are the upper holes drilled?
2 inches? 1 7/8 inches?
We really would like to know how far down the upper holes are drilled.... Thanks...
I would imagine if they are 2 inches down then that might put the lower holes slightly lower.
There is a possibility to cheat when drilling. Slightly drill up instead of 90º into the transom but this can be tricky...
At any rate, I think you will be fine with the 6 1/2 inch vertical spacing which means your engine will be mounted in the 3rd bolt holes in the upper engine bracket which is 2 holes up...
Edited by Joe Kriz on 10/08/09 - 9:29 AM |
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| Mr T |
Posted on 10/07/09 - 11:06 PM
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Joe you nailed it. They are at just over 2 inches, perhaps 2 1/16 or so. It threw everything off. I kept looking at the holes and thinking this should work, but it didn't. Finally I looked at the top and decided to checkit, and bang there it was.
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| bottomfish |
Posted on 10/08/09 - 8:26 AM
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That was the problem on my Montauk. When I pulled the motor it had be initially installed with the top holes 2 1/4" down making any lower bolts a non option. I plugged the whole thing and redrilled. I cheated the whole pattern up a 1/4" and hit the splaswell perfectly. It was done nervously but came out great. Another option I saw done on your type hull was a 6" hole was cut in the front wall of the inboard side of the splaswell just above the rigging tube. The foam was dug out and the bottom holes were drilled to allow throughbolting in the mid to lower range of the bracket. A 6" deck plate was then installed to provide access and keep out water. Interesting way to do it I thought.
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| Tom W Clark |
Posted on 10/08/09 - 8:27 AM
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Larry -- That's too bad that the original installer drilled all the holes too low.
The other thing you could just as easily have done is to drill the lower holes 6-1/2" below the top holes instead of drilling another set of blind holes.
It won't matter with your current motor, but if you ever repower, it would have allowed the new motor to bolt on without further modification.
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| Joe Kriz |
Posted on 10/08/09 - 9:39 AM
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I misread the part about you using blind holes again.
I agree with Tom, drilling the Green colored holes in the drawing which are at 6 1/2 inch vertical spacing would have allowed you to use any engine in the future.
Just goes to show us that those upper holes can vary and dictate which lower holes we can drill, the yellow colored at 7 1/4 inch spacing or the green colored at 6 1/2 inch spacing...
Edited by Joe Kriz on 10/08/09 - 10:03 AM |
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| brooks89 |
Posted on 10/08/09 - 12:35 PM
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bottomfish wrote:
Another option I saw done on your type hull was a 6" hole was cut in the front wall of the inboard side of the splaswell just above the rigging tube. The foam was dug out and the bottom holes were drilled to allow throughbolting in the mid to lower range of the bracket. A 6" deck plate was then installed to provide access and keep out water. Interesting way to do it I thought.
This is precisely what was done to mount my motor. I also like that I can unscrew the deck plate while the boat is in the garage for the winter, allowing any moisture in there to easily dry out.
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| Tom W Clark |
Posted on 10/08/09 - 12:45 PM
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I've seen it done many times myself but is one of the worst things you can do to a Whaler and COMPLETELY UNNECESSARY if folks can just understand that outboard motors do NOT need to mounted all the way down on the transom of a Whaler.
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| brooks89 |
Posted on 10/08/09 - 1:58 PM
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Not sure what you mean by "all the way down on the transom"? I have a 2000 70 HP Johnson and from the looks of it there's only one position the motor bracket would mount correctly on the transom...
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| Joe Kriz |
Posted on 10/08/09 - 2:10 PM
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brooks,
Take a look at this article that we have been talking about with the blind hole mounting.
http://www.whalercentral.com/articles...icle_id=82
When the engine is mounted all the way down on the transom using the upper bolt holes on the engine bracket and the lower blind holes, no one can raise the engine when mounted this way.
The blind holes are the problem as the motor is not using the lower slots in the engine bracket.
If the lower slots are used instead of the blind mounting holes, then the motor can be raised and lowered easily.
To utilize the lower slots, the lower holes have to be re-drilled in the location of the yellow or green colored holes in the drawing.
Edited by Joe Kriz on 10/08/09 - 2:16 PM |
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| Tom W Clark |
Posted on 10/08/09 - 2:52 PM
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brooks89 wrote:
Not sure what you mean by "all the way down on the transom"? I have a 2000 70 HP Johnson and from the looks of it there's only one position the motor bracket would mount correctly on the transom...
No, there are several ways a motor can be correctly mounted on the transom, not just one. That is why there are multiple bolt holes in the mounting bracket of outboard motors.
"All the way down" means as low as an outboard can be mounted. This usually involves the use of the top set of bolts holes on the mounting bracket and results in the "hooks" of the motor mounting bracket resting on the top of the transom, or nearly so. This is not an optimal motor mounting position.
On a 16'-7" Whaler hull, moving the motor up set of holes (3/4") will result is satisfactory performance with even the most old-fashioned aluminum propellers.
With modern stainless steel propellers, a "two holes up" position can and should be used.
Being able to raise the motor on the transom has the added benefit of negating the need to use lag bolts, or dig out foam or even use the non-standard blind holes on the OMC motors by allowing the BIA standard specification bolt spacing to be used instead, albeit compressed vertically a bit.
Edited by Tom W Clark on 10/08/09 - 2:53 PM |
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| Tom W Clark |
Posted on 10/08/09 - 3:25 PM
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Here is a photo of the motor on my last Montauk. You can see it is mounted using the second set of bolt holes. We call this mounting position "one hole up" for obvious reasons. The "hooks" are about 7/8" above the top of the transom.
Note the lower bolts are only 3/4" higher than normal. In other words they are 7-1/4" below the top bolts. There are full washers on the lower bolts in the splashwell and the washers clear the bottom of the splashwell by quite a bit. The holes were drilled at an angle but not much of one and more than it really needed.
At this mounting position, the Mercury 90 performed well with no ventilation or cavitation even with its original crappy aluminum prop. With the Laser II that later went on the motor, a "two holes up" mounting position would have resulted in even better speed, acceleration, fuel economy and lighter handling with less bow rise on acceleration and a reduced tendency to porpoise.
[img]http://www.whalercentral.com/images/engine_mounting_height.jpg[/img]
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| brooks89 |
Posted on 10/08/09 - 6:54 PM
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interesting... the hooks on my motor mount are resting on top of the transom with the upper bolts located in the second set of holes on the bracket, not the top ones. I don't recall off hand the location of the lower ones in relation to the bracket. When the boat comes out the end of the month I am going to take a closer look. I bought the boat like that and never thought about raising the motor. I have a standard OMC aluminum prop on the 70HP motor and can do about 35 MPH on flat water. Assuming I am able to raise the motor one hole do you think it would make a significant difference in performance?
Edited by brooks89 on 10/08/09 - 7:26 PM |
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| Mr T |
Posted on 10/08/09 - 7:21 PM
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I considered trying the 6 1/2 inch holes, but looking at the mount on the motor, it appeared that would raise me way above two holes on the top bolts. From all I have heard 1-2 holes is the right position, and I could see that the 6 1/2 position woul take me above that.
I do not anticipate changing the motor anytime soon as I am not cash rich, so it did not freak me out too much to go with more blind holes.
yeah,I chickened out.
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| Tom W Clark |
Posted on 10/08/09 - 7:43 PM
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Uh, the 6-1/2" spacing would have, in your case, resulted in a motor height somewhat below the standard "two hole up" mounting position, not above it.
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| Joe Kriz |
Posted on 10/08/09 - 8:34 PM
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T,
The bolt holes on the engine bracket are spaced 3/4 inches apart.
The colored holes are the same 3/4 inches apart.
Mounted all the way down the red hole would be 8 inches down which we can't drill and use thru bolts.
The yellow hole is 7 1/4 inches down from the top holes which would mount the engine in the second to the top bolt hole which is called mounting the engine one hole up.
And the green hole is 6 1/2 inches down from the top holes which would mount the engine in the third to the top bolt hole which is called mounting the engine two holes up.
We can see in Tom's photo above that his engine is mounted using the second set of bolt holes which is mounted one hole up and you can see the empty bolt hole above the mounting bolt.
We can also see that the lower slotted holes has the bolt in the top of the slot. This bolt is slightly above the center of the drain tube. As Tom mentions, this works but you have to be careful.
We also need to make sure that the upper holes are not drilled lower than approximately 1 7/8 inches or that also lowers the lower holes which may not clear the bottom of the splashwell.
If anyone can drill the hole using the yellow 7 1/4 inch distance down from the top hole, this would be the best situation.
I wouldn't suggest using a new blind hole at all but rather use the green hole at the 6 1/2 inch distance down which would easily clear the bottom of the splashwell and raise your engine 2 mounting holes...
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| Mr T |
Posted on 10/08/09 - 11:14 PM
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I must have missed something then. I looked at the drawing, looked at the motor, and the mount and for the life of me the lower slots were not going to mate up with any of the three settings, at 6 1/2, 7 1/4, or 8 inches.
Well too late now either way. I'm not going back in there until that current motor blows.
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| number9 |
Posted on 10/09/09 - 1:06 AM
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Joe,
FYI, I've tried to do some fact finding on the standard mounting holes for transoms. As you stated in the article the upper black holes and the red holes are spaced correctly for the standard. They allow for mounting in full down, full up or in between positions of motors with that hole pattern.
The standard is for vertical spacing between hole centers and horizontal spacing between hole centers or from transom vertical.
There does not appear to be a industry standard for the distance from the top of the transom to the top hole centers. Thought you'd find these examples interesting.
1. Template in Installation Manual for 1987 Mercury 70 HP calls for 1 7/8".
2. 2005 Honda Rigging Guide gives a 2.11 dimension from "transom board top" but also states "the upper bolt holes should be more than 1.3" from the top of the transom" about a 3/4" range.
3. 2005 Mercury Rigging Manual calls for use of their drilling fixture, no dimension given.
4. 2007 Yamaha Rigging Guide gives a 2.0" dimension from "transom top" and say to use a drilling fixture.
5. BRP drilling fixture dimension is approximately 2".
Bill...On the Ogeechee
1984 Outrage 18...Yamaha T50...that's right, 50hp |
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| Mr T |
Posted on 10/09/09 - 7:18 PM
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posted some pics up of the new installation in the two holes up position. As you can see, the top holes are at 2 inches from the top of the transom; the new blind holes are 6 1/2 inches below that, spaced at 10 3/4 inches. The slots are below that spaced at 9 7/8. It looks to me that the slot is 8 or 8 1/2 inches from the top of the transom down to around10 or so inches.
I posted up pics of the new holes from the splashwell, as well. The white spots are the marine tex covering the old holes, on the right side hole, you can see a dark spot on the left side of the white. That is where I drilled the pilot hole at 7 1/4 inches from the top hole. There was no way I was gonna put a 1/2 inch hole that close to the bottom of the splash well, hence the decision to make new blind holes.
Jeez my boat is dirty
Edited by Mr T on 10/09/09 - 11:14 PM |
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| modenacart |
Posted on 10/10/09 - 6:53 PM
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I assume that engine placement really has to do with where the prop is located. Is there a picture of where it should be? I have seen where the brackets are but not the prop. Thanks.
They that give up essential liberty to obtain a little temporary safety deserve neither liberty or safety.
--Benjamin Franklin |
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