So how tall is a 20'' transom?

[5150abf]

Are they actually 20'' or is it a different number

I was running a 25'' motor but the transom is actually like 22 3/4''.

Looking at possibly having to cut mine down for new motor but measured my set back and it is almost exactly 20'' from the top of the set back to the bottom of the boat.

That would be really cool if I didn't have to cut my hull.and the bottom bolt would miss the wood by a 1/2'' so would need to get creative there.

 

[Old Ironmaker]

Personally I would be very hesitant to cut down the transom. I cringe when I have to drill a hole anywhere on my boat let alone take a saw to it, that's just me though. Most likely you are going up in power or going to a 4 stroke, are you? What size of a boat do you have there? With either you are going to increase the weight on the transom. That leaves you more susceptible to getting backwash into your water well or over the transom and into the boat as well as more stress on the transom. If you do cut it you can bolster the bottom bolt opening by sandwiching aluminum to the transom front and rear. Buddy was maxed out on HP but thought he could go up 25 HP and a heavier 4 stroke. As soon as he splashed it he took on water through the drain ports into the water well and the top of the transom was dangerously low to the water.

 

[JimS123]

Boats are specified as short, long or extra long shaft. The 15, 20 or 25" transom height can vary with the manufacturer, based on their own design factors and performance data.

Most motor brackets have holes for vertical adjustment. Position the motor so the anti-ventilation plate is at or above the bottom. Its trial and error.

Don't cut the transom. Buy a motor shaft length that the boat calls for.

 

[5150abf]

Never mind.

I was always under the assumption my engine was a 25'' but it is a 20'', confirmed with the fine folks on the Evinrude board so I am good for the repower without cutting the boat, thank God for that.

I am also not real keen on new holes in the hull.

The boat is an 80 Sea Nymph 16' that I redid from the keel strip up 5-6 years ago, all storage wells and livewell lit, 400 watt stereo, camper top ect. ect, love the boat and being aluminum it should last forever.

Ironmaker, already thought of that.

old engine was @200lb, new is 247 and the boat rides pretty high, 10'' of gunnel above water line at the transom so don't think I will have an issue with wash.

Redid the transom a couple years ago, 2 sheet of 3/4 marine ply Gorilla glued together so the transom is good too.

Boat is rated for 70 and only going 50 so good there too.

Thanks guys