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Author Topic:   BW15 - raising motor - blind holes alignment with standard
russellbailey posted 05-03-2002 10:46 AM ET (US)   Profile for russellbailey   Send Email to russellbailey  
I'm the keeper of our family's 1980 Striper 15. It's on its second 70 Evinrude, a 1987 with power trim.

The motor appears to be mounted using blind lower holes - there are two bolts in about the right place and they seem to be snug from the inside. It is mounted all the way down. Also, on each side below the mount is what appear to be a zinc-like material apparently mounted to the hull - maybe a 2" wide, 1" deep, 3" high piece. I don't know what this is. I was 17 when the new motor was mounted and my father was in charge of the details then.

I've come to the conclusion the motor is too low. When we run, you can't even see the Doel-Fin or any sign of it. The cavitation plate is right at the bottom of the hull.

Question 1 - are the blind bolt holes in line with the lower mounting holes, only higher? If they are in line, I could use the same mounting holes just by raising the motor.

Question 2 - If #1 is true, how high would I have to raise it to use the standard lower mounting? My impression from others here is that you can raise it up 2-3 holes without a jackplate (it seems like the 15 may ride deeper and thus take more height than the 13 or 17). Would this be high enough to line up?

I realize I can determine this myself by unbolting it and moving it around on the transom. But, I'd rather first find out if someone knows.

I can't use a jackplate - we keep it in the garage and I already had to shorten the trailer tongue and knock out drywall to fit it in - the propeller sits inside the drywall next to the sheathing.


PS - hoping to waterski on Lake Lanier (GA) for the first time of the year this weekend.

Tom W Clark posted 05-03-2002 11:17 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
Yes the blind holes align with the lower mounting slot.

If you look at the mounting bracket on the outside of the hull you may be able to see the "bulge" where the blind holes are and thus be able to measure the minimum distance you can raise the motor. Probably a couple of inches.

Go ahead and experiment. It is not that difficult to unbolt and re-bolt the motor.

russellbailey posted 05-06-2002 11:05 AM ET (US)     Profile for russellbailey  Send Email to russellbailey     
Thanks for the reply Tom. I think I'll have to go up two holes and it should work. I had to get some additional nuts this weekend - the bolts in the blind holes are identical to those in the top and will work, but obviously did not have nuts on them.

As far as I can tell, the bolts on there are not high strength - they are simply 1/2" with 13 tpi, stainless. The nuts are plain - I plan to use LocTite on them when I put them back on.

I've searched the site for info on whether to use polysulfide (e.g., 3M 101) or polyurethane (e.g., 3M 4200) when I re-bolt the motor. My impression is that either is fine, though it sounds like 101 would be preferred. Any suggestions?


Tom W Clark posted 05-06-2002 11:41 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
Generally speaking, stainless steel fasteners are comparable to grade 5 fasteners. All the outboard (larger than 40 hp) mounting bolts I have seen are 1/2" x 13.

You should not use regular nuts but rather nylock lock nust for security.

You can do it either way buy I like the nuts to go on the outside of the transom. That leaves the bolt heads on the inside where it looks nicer.

You can use either polysulphide or polyurethane caulk. You can use silicone too for that matter, but whatever you do, use something with low adhesion. This is one instance where 3M 5200 is inappropriate.

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