RPM"s running a bit high

[wcsparky05]

'89 merc 4 cyl 3 ltre 140 hp
used to run wot at 4500 now runs over 5200. new plugs,oil, thermostat, impeller, fresh water, what didn't i do right? still runs great but i am concerned. and it did stall on me for the first time ever last week. that wasn't cool in front of the chicks!! prefer for that to never happen again.thx.

 

[Bondo]

Re: RPM"s running a bit high

Is the boat Noticeably Faster,..??..??......

Hard to Believe a Tune Up would get you an Extra 700rpms.........Musta been a real Dog before.........

Might be time for a New Bigger Prop........

 

[cheburashka]

Re: RPM"s running a bit high

'89 merc 4 cyl 3 ltre 140 hp
used to run wot at 4500 now runs over 5200. new plugs,oil, thermostat, impeller, fresh water, what didn't i do right? still runs great but i am concerned. and it did stall on me for the first time ever last week. that wasn't cool in front of the chicks!! prefer for that to never happen again.thx.

I'm not sure if this engine has electronic ignition or not. If it has points, did you reset the point gap? If so, you may have changed the dwell and the timing. Overly-advanced timing could cause the higher rpms. In any case, I'd check the timing. Could be it was retarded before the tune-up and is right now, but if it's too far advanced it could cause problems later on.

 

[Don S]

Re: RPM"s running a bit high

I've seen it happen when people reprop their boats instead of fixing the engine. You have to have the dwell, timing, carb mixture, and idle speed all to specs, then it will run and idle properly.
Did it die when you took it out of gear???? That could indicate a faulty shift cable.

 

[wcsparky05]

Re: RPM"s running a bit high

no, bond-o, never was a dog. does about 35 i think with 5 people. no, not any faster just higher rpms. but the tune up was this winter and just recently the rpms went up. is that a good thing? and my prop is brand new this winter. 14.5 /17. thx everyone, i guess i'll check the timing.