Mounting 2020 Merc 30 EFI on 2021 Lund SSV-16

[Albertan]

After a *long* search, I finally managed to find an outboard for my new tinny. The Merc was my second choice, but I'm not complaining with the shortage of outboards this season.

I tried to research as much as I could about mounting the outboard to the boat. This is the first time I have tackled it myself. I've seen some conflicting info about mounting height, so I went ahead and mounted it where I think it's correct and thought I would get some feedback before sealing it to the transom. I know a test run would be ideal, but I'm trying to get ready ahead of time and I'm hoping I won't have to remove it once it's sealed down.

Speaking of sealing the holes, I'm still debating whether it would be better to use marine-grade silicone or 3M 4200...I have both. 3M 4200 is a little more permanent, while I think silicone might be a little better at dampening any vibrations. Any thoughts on this would also be appreciated.

Without further ado, this is where I have it mounted now...

 

[Weldorthemagnificent]

It looks good and will probably be good but I always like to prove something out before drilling holes. I use a shim, piece of wood, under the clamp to space it up and water test it first before permanently mounting. Like I said, it'll likely be fine but you'll hate it if it cavitates on the turns. A jackplate seems like a good option for tunability here.

Sent from my CLT-L04 using Tapatalk

 

[Albertan]

Well, I already drilled the holes using Mercury's Transom Drilling Fixture (jig). It's in the third hole in these pics, so I can raise the motor one hole or drop it two. I'm comfortable somewhere in that range is where I need to be. I could do a jack plate if it came down to it, but I'm not really concerned with eking out the last .2 mph on this boat...I have a 21' glass deep-V with a 300 Zuke for when I need to cover big water fast. This boat is primarily for mapping lakes and fishing small electric-only trout lakes in my area. I'm more concerned with it staying up on plane at low speeds rather than it's top speed. I realize a lot of that will come from propping.

 

[cody0707]

I think you are really close to where it needs to be. I don't think you will need to lower it. Try it where it is now then try it using the top hole and see which one performs better. The telling sign is where the cavitation plate is in relation to the water's surface while you are on plane.

 

[MrGiggles]

Choice of silicone will have zero affect on vibrations. The mounting plate is still in direct contact with the transom.

3M 4200 is a good choice. It is a lower strength product that is designed for applications that may need to be taken apart in the future. That said, I sealed my engine mount bolts with 5200 (the high strength, permanent product) and had no trouble loosening them to adjust the motor.

As for the motor height, you'll just need to get it on the water. All hulls perform differently, and the prop can have a big affect on it as well. If you can feel it ventilating out of the hole or while turning, it needs to be dropped a little.