By the way... I recently tested a 15 HP 4-stroke Mercury on the same 1996 Lowe 1248 mentioned above.
The owner ran a rowing school, and having the motor run well could mean life or death. They sometimes had kids flip boats, or get too close to the rapids, and they needed a reliable engine to do rescues. This meant that I had to thoroughly water test the engine after repair.
Since the 15 uses the same block as the 9.9, I figured it would be fine on the 1248. The Lowe was rated for 9.9 HP and 3 people.
The motor was considerably bigger, but it looked good on the boat:
View attachment 114054
I dropped the boat in, and noticed that the nose sat pretty high, but didn't pay attention to how low the back was. (Lesson learned) It looked fine, looking down at it:
View attachment 114055
Notice that I had put the battery and fuel tank as far forward and the cable and hose would allow. I thought that would give it deent balance to offset the heavier motor.
But I was wrong.
Right after that picture was taken, I stepped in the boat, onto the back bunk. The back corner of the boat dipped below the surface and about five gallons of water jumped in instantly. Shocked, I jumped to the front of the boat, and then back up onto the dock. That was a close one! A few more seconds and that boat would have gone down.
I used a minnow bucket and dipped the water while laying down on the dock. I pulled the fuel tank forward and then tried to see if sitting in the middle bunk and reaching back to control the motor would work.
It seemed better, so I putted around in a circle, but anytime I gave it any throttle, the back would squat almost to the surface, and I would back off quickly. Could not get it up on plane safely. No tiller extension made it too dicey.
If I could have moved the battery and fuel well forward, plus an extension handle on the tiller, I think it would have been okay, but I didn't have any extensions with me. I loaded the boat up and got out of there, REALLY glad I didn't sink the boat.
I ended up testing the motor on a 16' boat, and it ran great, no issues. The problem had been a perforated diaphragm @ the accelerator pump of the carb flooding the motor. So a kid would flip a boat, and the instructor cou
If you go with a 4 stroke, be careful until you find the balance of the boat. If your boat has a 20" transom, you will probably be fine, but test carefully first.