How fast should a 2 stroke 90 hp mercury go on a 17ft. bayboat?

Question

I just bought this boat.It,s a center console fiberglass bayboat .I took it out for the first time the outher day on a small lake and tried it out.It was slow coming out of the hole and seemed to lug with the motor trimmed down as I trimmed up to get on plane I was only able to get up to 25 mph.The guy I bought it from said it would run 45mph with 2 people in it.I owned a lot of boats but never a center console maybe I,m doing something wrong.I checked fuel filter and spark plugs and fuel lines they are good but the motor does idle slightly erratically.Got any ideas? thanks

Answer 1

change your spark plugs.

I would think close to 40 MPH

you must have a cylindar not firing.

Answer 2

Mixture, Prop. Those things will give you different power or speed.

Answer 3

My question to you is how long did the boat sit before you bought it?  Sounds like the carbs might have a issue especially if it sat around unused.  I have a 17 ft. Maycraft with a Merc 90 two stroke on the back and it tops out at around 45 mph.

Answer 4

If you have an erratic idle you should put a timing light on each coil wire and make sure they are firing STEADILY. Also move the wire around while testing to make sure moving them doesn't cause erratic fire. If all coils are firing correctly pull plugs out and make sure you have a strong blue spark. If they look dirty just replace them it don't cost much. If the plugs are firing good the problem is most likely fuel system. Make sure you mixed your gas/oil right and using correct oil for motor. Next step would be to clean the carbs with a good carb dip. I would say with 2 people on there it in optimal running condition it should go 35 not 45 though. Keep the trim at about 75% down to keep boat running higher in the water.

Answer 5

working on boats i think it should do at least 35 make the bilge is dry other than that it is a prop issue  if the engine is running properly

Answer 6

There are a lot of other variable including prop., payload, fuel mixture etc.   My experience would say 30-32 mph tops!