Lower RPM on one engine

[ACO175FO]

Hello everyone, this is my first post here, so thanks for the help in advance.

I have a 2009 SX210 that I bought used several months ago. It has been running very well for me all except on minor issue. The right side engine will only get to about 7000 RPM on the water. The left side will go slightly above 8000. RPMs on the right engine also seem to flutter a bit at any throttle setting.

At first I thought it was an issue with the throttle cable as the right engine cable would not go all the way to the throttle stop. I tightened the cable and now it will go all the way to the throttle stop, but I'm still having the slightly low RPM issue.

When I have the boat out of the water to flush the engines the right engine will go above 8000 RPM the same as the left. I am not sure what else I should be checking. Oil level appears to be right directly in between the full and low marks on the dipstick.

 

[Babin Farms]

When was the last time the spark plugs were changed??? I would change them out to see if if they’re your problem.

 

[buckbuck]

I agree with @Babin Farms about changing plugs and would recommend you never take an unloaded engine to max rpm. Be careful.

 

[ACO175FO]

When was the last time the spark plugs were changed??? I would change them out to see if if they’re your problem.

Previous owner said he changed them every year, if true they were changed last season. I think I will go ahead and change them now anyway. Any idea what size spark plug socket is needed for the MR1 engines?

 

[buckbuck]

The typical 5/8".

 

[ACO175FO]

Changed the oil and spark plugs today. Minimal fouling on the plugs, although the ones on the right engine did look worse. The oil filters were tough to get off, must have been over torqued the last time. I only managed to pump out about 1 1/2 qts from each engine. Also pulled the air filters and washed them.

Test run possibly tomorrow morning.

 

[ACO175FO]

Took the boat out on Saturday and everything worked great. Both engines making about 8500 RPM at full throttle and got it up to 43 knots.