76SeaRay
Lieutenant Junior Grade
- Joined
- Aug 24, 2017
- Messages
- 1,047
Finally got the boat moved to my shop in Washington state and getting a chance to move forward on restoration.
I started the restoration work on the transom. The transom measures about 3 feet high and about 7 feet wide on the inside (more like 4 feet high on the outside) and I have pulled out most of the plywood. Lower foot was pretty saturated with water and so are the stringers. I cut the floor and stringers back from the transom about 8 inches wide across the stern and cleaned out the hull of foam and wood to get to the bare hull. I am leaving the rest of the floor and stringers in place until I complete the transom replacement for added stability of the hull.
So, now for two questions on the transom.
First, the boat had an OMC outdrive and I am going to a Mercruiser Alpha 1. The specs call for the transom thickness to be 2 inches to 2 ¼ inches. The inside of the hull behind the transom wood is cleaned off and I measured the hull thickness at the OMC opening. It tapers from the bottom to the top of the OMC cutout. At the base it measures 0.550” thick on the port side to 0.604” on the starboard side at the edges of the OMC hole. At the top of the OMC hole it measures 0.460” thick on the port side to 0.439” on the starboard side. I need to find a tool to measure it farther out to see if the taper runs all the way across the transom. I am wondering the best way to make it flat for mounting the Alpha. Assuming the outside of the transom (gelcoat side) is flat, then the taper bottom to top is on the inside and underneath the plywood. Should I sand away the excess thickness at the bottom of the transom or add glass at the top before replacing the transom wood? It looks like the magic number for hull thickness will be 0.50 inches. Would it be better to lightly sand the bottom and fill at the top maybe to get it flat over the Alpha mounting surface?
Second, I need to buy the new transom material so what layers of resin and glass should go between the new board and the hull? I understand that you should put a layer of fiberglass on the hull to bond the new board. I am new to fiberglass so how thick will this bonding lay-up be and then how thick will the top finish layer(s) of resin and fiberglass be? Need to know the stack up of thickness so I can order board to meet the 2 inch to 2 ¼ inch specs. Right now I am leaning towards Coosa board in 1 ½ inch thickness but that might be too thick once glassing is done. Next size down in Coosa board is 1 inch but I don’t want to do a lot of fiberglass build up either.
Thanks.
I started the restoration work on the transom. The transom measures about 3 feet high and about 7 feet wide on the inside (more like 4 feet high on the outside) and I have pulled out most of the plywood. Lower foot was pretty saturated with water and so are the stringers. I cut the floor and stringers back from the transom about 8 inches wide across the stern and cleaned out the hull of foam and wood to get to the bare hull. I am leaving the rest of the floor and stringers in place until I complete the transom replacement for added stability of the hull.
So, now for two questions on the transom.
First, the boat had an OMC outdrive and I am going to a Mercruiser Alpha 1. The specs call for the transom thickness to be 2 inches to 2 ¼ inches. The inside of the hull behind the transom wood is cleaned off and I measured the hull thickness at the OMC opening. It tapers from the bottom to the top of the OMC cutout. At the base it measures 0.550” thick on the port side to 0.604” on the starboard side at the edges of the OMC hole. At the top of the OMC hole it measures 0.460” thick on the port side to 0.439” on the starboard side. I need to find a tool to measure it farther out to see if the taper runs all the way across the transom. I am wondering the best way to make it flat for mounting the Alpha. Assuming the outside of the transom (gelcoat side) is flat, then the taper bottom to top is on the inside and underneath the plywood. Should I sand away the excess thickness at the bottom of the transom or add glass at the top before replacing the transom wood? It looks like the magic number for hull thickness will be 0.50 inches. Would it be better to lightly sand the bottom and fill at the top maybe to get it flat over the Alpha mounting surface?
Second, I need to buy the new transom material so what layers of resin and glass should go between the new board and the hull? I understand that you should put a layer of fiberglass on the hull to bond the new board. I am new to fiberglass so how thick will this bonding lay-up be and then how thick will the top finish layer(s) of resin and fiberglass be? Need to know the stack up of thickness so I can order board to meet the 2 inch to 2 ¼ inch specs. Right now I am leaning towards Coosa board in 1 ½ inch thickness but that might be too thick once glassing is done. Next size down in Coosa board is 1 inch but I don’t want to do a lot of fiberglass build up either.
Thanks.