Yamaha AR 230 RPM DROP

[crowleyp]

Hi all, I have a 2008 Yamaha AR230 with about 145 hours. I change plugs every year, ignition coils as needed. But I have had a recent unexplained RPM reduction, where both engines used to spin at 10500, then one , then the other can only max at about 8700 RPM. I checked throttle cable adjustment and they are up against the stops so no further adjustment. My intakes and exhaust's are clear, auxiliary cooling exits are functioning and the impellers are not cavitating. Boat receives annual maintenance oil change etc. Any suggestions?

 

[Scottintexas]

Glad to have you on board, update your profile with your location so we know where your at,

most of us MR-1's change plugs every year or two but very few ever have to change coils,

I wonder since it's both engines if it's fuel related, either bad fuel or maybe you picked up some water in the tank?

maybe disconnect the fuel line and pump some into a glass jar and let it sit for a day to see if water is there,
otherwise try to run it low and fill up with some quality fuel to see if it helps,


.

 

[Beachbummer]

I'm hunting for a similar problem. Most everyone else that has it fixes it with new plugs. I would replace plugs to troubleshoot if you haven't already.

While you are at it, you can swap coils with the other engine to see if it follows.

 

[crowleyp]

Hi all, i changed plugs in the beginning of this season and my port engine was at 10500 rpm and a week later all can get out of it is 8700 rpm. I had a coil crack which needed , (starboard side )replacement but when they go it’s not gradual at all. Do you think my new plugs have gone bad so soon ? Maybe replace with higher end plug ? I think if it were fuel related my other engine would had dropped off even further no? I’m puzzled by this , I’ll try and replace the plugs as that’s the least expensive option for now

 

[Scottintexas]

the MR1's are extremely sensitive to plugs (especially if you're only turning 8500rpm and have had coil issues previously)

be sure to look at the link in my sig. below for common issues with our model boat, especially the scupper valve,


.

 

[crowleyp]

the MR1's are extremely sensitive to plugs (especially if you're only turning 8500rpm and have had coil issues previously)

be sure to look at the link in my sig. below for common issues with our model boat, especially the scupper valve,


.

Thanks Scott, so you are familiar the ignition coils I have sit right on top of the spark plug so there are 8 of them , only one had to be replaced as the plastic housing just cracked ...thanks