I have a single 1967 Mercury 50hp outboard motor and I would like to make it into a double outboard with another 50hp motor same as I already have. The transom is rated for it. I am wondering if I need to do anything to the motors to run them the same? Or can I just stick it on to the back and go? Thanks
I assume you have a Reinell, by your name. But what model? When you say "its rated for it" are you referring to the HP capacity? You need to have space to mount both motors side by side--typically they are 20-inch centers--to allow for turning and to be able to remove the cowlings for service. So, first, figure that out,
Second, you wont likely be able to use your existing motor as one of the twins. Right now, your motor is mounted on centerline. Two engines side by side require shorter shaft lengths becaiuse the V of the hull rises as you move outboard, and the anti-ventialtion plate needs to be mounted within 1/2" of the bottom.
This leads to point three. Your boat, a Reinell, is older and probably has a 20-inch transom--it may even be 15 inches, Yoou need to measure vertical distance from the top of the transom to the bottom at the position that each motor would be located. Then you buy engines with that ( close) shaft length. You will probably need a pair of 15-inch shaft motors for twins on your boat.
You wont find counter-rotating engines in such short shaft lengths or small horsepower, but thats not a concern as 100 total HP isnt too bad to steer with, though your boat will pull to starboard more than normal due to the extra torque created by the second prop.
If you want to go faster, repower with a single 90 or 100-hp . If you want the "get hoime" guarantee of redundant motors, add a 5-HP kicker. Personally, I see no benefit in rigging your boat for twins.