Motor Mount / Backing Plate

[bergskvb]

I recently purchased an O'Day 25 and need to install a motor mount for an outboard engine - a 4 stroke, something in the 8-9.9 range. I understand there are some issues to consider particular to the O'Day 25 transom to be sure the mount is level and reinforced. I would appreciate any input from folks in the group that have experience with this installation on an O'Day 25.
Thanks

 

[Ward H]

Check out this thread if you have not yet seen it. http://forums.oday.sailboatowners.com/showthread.php?t=147539

In it are a couple of photos of the motor mount on my 25. You will see my bracket is mounted flat on a rectangle of 3/8" (by sight, never measured it) material, which is screwed to the transom. On the inside there is a backing plate of equal size but thicker, epoxy coated plywood. The bracket bolts through to the inside of the backing plate.

I'm 6' and 235lbs and probably could get to the backing plate if needed. If you are larger you might want to find someone a bit smaller to go down and reinforce the inside.
You can see the area where the backing plate should be installed from the port side rear berth. The inside wall of the berth is hinged so it drops flat for access to that side of the area under the cockpit.

Other boats have the bump which angles the bracket down. Don't know if mine did oringally but my set up works well. I do like the hydraulic assist lift for the 115lb 9.9 Yamaha XL shaft.

Being flat to the transom my outboard is slightly off square to the centerline of the boat. When the OB tiller is straight it does turn the boat slightly. I may shim it square in the spring but I don't motor very far so it is not a problem as it is.

I see no need for the bump and I wouldn't worry about it being level, just be sure to reinforce the area inside and out. My bracket and OB have plenty of trim adjustment to account for being flat to the stern.

 

[bergskvb]

Took a look at the post and it is a lot of help. thanks for the information and the quick response! Merry Christmas

 

[Ritdog]

I think the standard Oday mount was the wedge / bump with the motor mount bolted through that through the hull.

My 25 had been rear-ended, and the 3/4" sheet of plywood poly'd to the inside of the transom was cracked in half, from top to bottom. Strangely, the fiberglass and gelcoat were fine - go figure. That plywood was also original to the boat.

I had to grind the whole thing out with an angle grinder in 90 degree weather, and let me tell you, it ws one of THE nastiest jobs I have ever done. I did the king plank down the middle too, as that was getting soft. There was no wood to port.

After it was all gone, I put in a new kingplank 8" wide, polying it to the hull. Used the gudgeon holes to snug it up with bolts. Then cut 3 30" square pieces of 8mm, shaped them to the profile, and snuck that them there one by one with CSM and thickened poly too. I had drilled and filled the bolt hole locations with 1" holes and EPOXY , drilling 1/4" holes in their middles for the mounting bolts. Didn't want any water penetration back there! The bolts tightened up the 8mm, bending it to fit nice and snug against each layer.
Then, poly-puttied the edges all around so the valleys were flush, and added 3 layers of CSM to seal the whole thing.
Just nasty from start to finish : hot, scratchy, stinky, sweaty, etc. Took a week.
Used ss fender washers for the bolts, and the whole thing is bomb-proof...or at least until it gets rear-ended again!

Whatever you do, make sure you back up those bolts with the mount.

Note too that you will have to probably heat the bolts snugging the plywood up with a torch- JUST hot enought to loosen them ...use over-long bolts with nuts on the outside.....

 

[bergskvb]

Thanks for the insight. Fortunately for me I am starting from scratch with the back-up plate. Appreciate the help guys!