I am temporarily changing outboard engines. The mounting bolt pattern on the temporary engine is different from the mounting pattern on the engine already on the transom.
Q: What is the best method to fill the transom mounting holes so that I can re-use them later?
I was thinking of using wood dowels to fill the space in the transom wood while leaving a 0.125-inch to 0.250-inch depression below the gel coat. Then fill the depression with epoxy so it would be waterproof.
Temporary Engine Mounting
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Re: Temporary Engine Mounting
Of the two engines involved, which engine has the mounting holes in position according to the BIA standard: the temporary replacement engine or the permanent engine?Oldslowandugly wrote:I am temporarily changing outboard engines. The mounting bolt patterns on the temporary engine is different from the mounting pattern on the engine already on the transom.
What is the duration of the use of the temporary engine?
Re: Temporary Engine Mounting
Don't use a dowel. Cut a plug from marine plywood to fill a large diameter hole in the transom as would occur with an old engine mounting bolt hole, and avoid the mismatch in the wood grain orientation.Oldslowandugly wrote:I was thinking of using wood dowels to fill the space in the transom wood...
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Re: Temporary Engine Mounting
The 48-HP engine has the BIA standard mounting hole locations.jimh wrote:Of the two engines involved, which engine has the mounting holes in position according to the BIA standard: the temporary replacement engine or the permanent engine?
The temporary 30-HP engine has two of the old-time thumbscrew clamps as well as a couple of bolt mounting holes farther down the engine mounting bracket.
The bolt holes are one half inch diameter right now. To match the thickness of the transom I guess I would need several half inch plugs of plywood to fill the holes with. The thickest marine plywood I have is only one half inch thick.
The temporary motor will probably be on for the entire 2021 boating season. After that then those holes will need to be filled as well.jimh wrote:What is the duration of the use of the temporary engine?
I don't understand what you said about the grain orientation.
Would that cause a dowel to be stressed?
Re: Temporary Engine Mounting
Cover the existing BIA-located holes with duct tape.
Clamp the 30-HP on the transom. Drill the minimum diameter hole for any new holes. You don't need a 0.5-inch diameter bolt for a smaller engine.
Clamp the 30-HP on the transom. Drill the minimum diameter hole for any new holes. You don't need a 0.5-inch diameter bolt for a smaller engine.
Re: Temporary Engine Mounting
If you insert a dowel into a transom bolt hole and then cover it with epoxy, it will crack due to the shrinkage of the dowel. The grain of the dowel is going perpendicular to the transom face.
Hardwood plugs are recommended. The grain of the plug runs parallel to the transom.
Hardwood plugs are recommended. The grain of the plug runs parallel to the transom.
1992 Outrage 17
2019 E-TEC 90
2018 LoadRite 18280096VT
Member since 2003
2019 E-TEC 90
2018 LoadRite 18280096VT
Member since 2003
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- Posts: 719
- Joined: Fri Jan 15, 2016 11:19 pm
- Location: Queens NY
Re: Temporary Engine Mounting
I removed the 48hp motor today. The bolts were one half inch but the holes were slightly larger. Phil, I had a 9/16" hardwood rod so I used that. The transom measured two inches thick so I cut the rod into 1.5" lengths. The 9/16" wood plugs fit very tightly into the holes. I left about 1/4" open at each end. That worked well as the wood filled where there was wood, and I used epoxy to fill the 1/4" where the gel-coat layer was. I am confident no water will get in. When I need them again, I can just drill the epoxy and wood filler and have my holes back. Tomorrow I will hang the 30hp motor and make new holes for that mounting pattern.