How loud should a 3.5 ho Merc. 4-stroke be?

I just bought a used 2007 Merc 3.5 hp 4-stroke from a used boat place here in Crystal River, FL. At idle it is darn near silent but at my trolling speed, it is far noiser than my old 3hp 2-stroke Johnson. Trolling speed is about 3kts on my little 10' Jon Boat.

I thought it was a little noisy in the test tank but dismissed it as being in the tank. The first time I tried the engine on the boat it cranked then made a loud pop and nothing. It wouldn't crank after that. I took it back to the boat place and they found a broken crank shaft. The bolts appeared to have backed out. I spent $92 for parts.

Yesterday I put about 45 minutes on the engine. I got tired of the noise at trolling speed. At cruise speed, maybe 5mp, it is is 2-3 times louder than my old 2-stroke Johnson. I cannot put up with the noise.

I wouldn't sell the engine to anybody because I don't believe in screwing folks. I'd like to sell it back to the dealer or get the dang thing fixed.

Any suggestions as to what the problem might be?

Re: How loud should a 3.5 ho Merc. 4-stroke be?

A single cylinder engine, 2 or 4 stroke, is normally 3-4 times as loud as a JohnnyRude 3HP twin. I often compared my JW-13 to a Singer sewing machine.

Re: How loud should a 3.5 ho Merc. 4-stroke be?

It's just the exhaust system. Trade it up at the dealer and get rid of it.