4 Stroke Question

[Scott Smith]

I have a friend coming over tomorrow with his new boat. I will be installing an on-board charger for him (he can't tell the difference between a hammer and a screwdriver).



He has a 25 hp Yamaha 4 stroke on the boat, it's brand new. He's had it out once and claims that the motor runs a little rough and is unusually loud for a 4 stroke after everything he has heard about them being so quiet. This is all the info I have right now.



Not knowing much about the 4 stroke motors, is this normal for a new one..? If not what are some basic things I/We could look into as to why this is happening...? Does the mixing oil with the gas during break in procedures pertain to the 4 stroke motors also..?



Thanks for any info...

 

[Steve Rizza]

Maybe he had it running with the motor out of the water.I had a pontoon with a Honda pass by while I was fishing one day,and could barely hear it running.

 

[TrepMan]

I rode in a guide's boat down here with a Honday 225 4stroke and MAN that thing was quiet at idle (never knew he had it on!!).



One thing I DO KNOW is do NOT mix OIL AND GAS in a 4 stoke!!! A 4 Stroke is what your car/truck is, and OIL directly into the gas will do a LOT OF HARM! I know Bob B. and the motorheads will pop in soon, but DO NOT add oil to the gas!!

 

[Lon Weekly]

I've got a Merc 60 hp 4 stroke and as Scrawney! said, "NO oil in the gas!" Mine's been quiet since day one. I can't think of anything that should make it run rough, but make sure he didn't put any oil in the gas.

 

[Bill Gintzel]

I also have a 4S Merc 60 and can carry on a conversation with my boatmate at full throttle without raising my voice.



If he used any oil in his gas he may have a problem. He should at least remove and clean the plugs and purge the system with clean oiless gas.



I haven't seen any Yamaha 4Strokes but the Hondas are very quiet.

 

[Greg. Avery]

smitty I have a 4 stroke Yamaha 50 hp & you can't tell if it is running , NO oil mix. If he ran

it out of water it is no quiter then any other motor.

 

[Anotherdink Scott Chambers]

my bro has a merc 115 4 stroke ( think yam makes all the larger merc 4 srtokes, just re caled)and in the water it is really quite, we can actually talk normal level while on plain, and I have asked him before if his motor is on at the ramp before I float him off the trailer at the ramp, he just laughs and nods his head.

 

[Michael Frank]

I'll go along with what everyone has said, most four-strokes are very quiet at idle. We have a Johnson 140 4-stroke on our tri-toon, and you can't hear it running while sitting at the helm at idle. Very smooth, and the noise level is mellow even at full throttle.