Will running low RPM's on Mercruiser for sustained period hurt engine.

[hz293]

I have a Mercruiser 5.0 engine with Alpha 1 Outdrive. I have recently taken up salmon fishing on the Columbia river but this is not a fishing question. I was trolling with my Chaperral 19 ft for the first time at between 700 to 900 RPM's. My question is if running the engine at those RPM's for a sustained period, 2 to 3 hours, will it cause any type of problem with my engine or Outdrive.

 

[Scott Danforth]

if your engine is in good shape, thermostat is working, cooling system working, then no. troll on.

if your thermostat is stuck open, you may run too cold (excessive wear)
if your motor has questionable rings and blows a lot of oil, you may foul a plug

 

[hz293]

Thanks, engine is in good shape, just replaced water pump impeller and it's keeping it at a good temperature. I shall roll on and since you were the first to take the worry off my shoulders, I shall name my first fish after you. Thx

 

[Scott Danforth]

only if you grill it over an open fire with lemon pepper and butter

 

[fishrdan]

The only thing I can think of that's different is you need to lube the gimble bearing more often if trolling, something like every 100 hours. I troll with my old 140HP Mercruiser, and just grease the gimble bearing during the yearly drive service,,, since my gimble bearing is not externally lube-able.

Make sure the carb's idle is adjusted well when the engine is; warmed up, idling in gear, with the boat putting along. You should be able to go in-out of gear with out the engine hick-upping. If the engine loads up and starts stumbling, and you have to raise the RPM's to get it idling well again, go back and adjust the idle. Too lean and too rich are both bad, you have to find the happy medium.

 

[ondarvr]

Your bigger issue would be going slow enough for this fishery. I frequently see people troll with their I/O's going far too fast for the location, species or method, sometimes it's OK and other times it's just way too fast. That's why you see virtually every fishing boat using a kicker in the NW.

 

[Scott Danforth]

Your bigger issue would be going slow enough for this fishery. I frequently see people troll with their I/O's going far too fast for the location, species or method, sometimes it's OK and other times it's just way to fast. That's why you see virtually every fishing boat using a kicker in the NW.

agreed, you may need to back the RPM down. in my 3.0 powered Avanti when trolling, we would use the 15P prop and when going with the wind, back the RPM down to 500 RPM for trolling.

 

[Chad Flaugher]

I run a happy troller trolling plate on my 190 hp I/O. I can get down to 1 - 1.5 mph.