Question for Factory Techs

[Mike722]

The boards are loaded with people wanting to know what hp engine to get. Most answers include the maximum because you can always throttle back.

I want to know if the engine makers agree that running an engine at half throttle will not affect the performance or life of newer engines over time? Does 4-stroke vs 2-stroke matter?

I am looking for what the manufacturers are telling dealers and techs, not what is in the owners manuals or owner's experiences.

I ask because the lawn and garden equipment that I sell and work on, needs full throttle all the time. It isn't in the manuals, but the factory reps and during factory training will stress that the customers must run at full throttle for the best performance and long life. The reason given is that the engines will not get hot enough to work as designed.

 

[tashasdaddy]

Re: Question for Factory Techs

those engines don't have a water cooled system, and thermostat. the thermostat on an outboard is there to keep it at the optimum temperature, at all speeds.

 

[Silvertip]

Re: Question for Factory Techs

Full speed (3600 RPM governed) on a lawn mower, snow blower or garden tiller is a little different than 6000 RPM on an outboard.

 

[JUSTINTIME]

Re: Question for Factory Techs

u are talking about oil cooled vs water cooled

if u run at a lower rpm on oil cooled the oil does not circulate oil that good

water cooled is always cooling due to the water pump

 

[deejaycee_2000]

Re: Question for Factory Techs

Full speed (3600 RPM governed) on a lawn mower, snow blower or garden tiller is a little different than 6000 RPM on an outboard.

I agree ....

 

[Mike722]

Re: Question for Factory Techs

My shop experiences, with the small engines, are that water cooled engines (Radiator and thermostat equipped) have more problems than the air cooled ones, if they are not run at full throttle. The problems include fouled spark plugs, excessive carbon, and moisture build up in the crankcase. On new engines, the rings may not set themselfs correctly.

My gut feeling was that the a boat engine is always under a pretty good load and has higher rpms, so they will build up enough heat to run right at most throttle settings.

From what I am seeing here, is that the factories are not mentioning this to the dealers or techs.

Thanks for your info
Mike

 

[rodbolt]

Re: Question for Factory Techs

and raw water cooled EFI motors, slightly overpropped, add a whole new dimension.

 

[Texasmark]

Re: Question for Factory Techs

Dhadley can fill you in on combustion temps inside OB engines.

OB engine spark systems are deliberately designed to remain at full advance for a time as the throttle is reduced.....One mfgr calls it "back drag". And the purpose is to improve fuel economy. They designed it in and they feature it. So they must support the theory.

Course you have to factor the boat's performance into this. If you are running a fast hull, like the one in my Avatar (logo pic on the left side of the post) I can throttle back to 4000 rpm's before the boat starts settling in the water......loading up the engine. On a heavy hull, or one that pushes hard, like a deep V, you could really be putting a load on the engine if you cut her back.

And, like D and others have said, the OB is constantly pushing the boat; the lawn equipment runs unloaded quite a bit. Also, on BS air cooled engines, I think they want the rpm's at 3600 to insure that the cooling fan is cooling properly.........course I run air cooled Hondas and Kohlers at significantly less than rated rpms, with syn oil that I change annually and have nothing but stellar performance. I had a Kohler lawnmower that was 5 years old and peeked thru the sparkplug hole one day and I could still see the crosshatch pattern from the cylinder hone when it was built.

So, I'd say it depends.

HTH

Mark