Prop/RPM Question

[rutcutter]

Although this does not apply to my boat I was thinking about it over the weekend. My question concerns 2 stroke and 4 stroke RPMs. I understand propping a motor to run in the upper limit of it's RPM range to avoid lugging the motor. Is this as important in a 4 stroke as opposed to a 2 stroke? They are certainly 2 different animals. In the 4 stroke it seems to me that as long as you do not exceed max RPMs that it would not be as important.
Your info is greatly appreciated.

 

[Bondo]

Re: Prop/RPM Question

Is this as important in a 4 stroke as opposed to a 2 stroke?

Yes....

 

[Silvertip]

Re: Prop/RPM Question

Yes it is just as important and what makes you think that it isn't? It doesn't matter if the engine is a two stroke, four stroke or a wankel -- if that engine cannot reach the manufacturers maximum recommended WOT RPM you are lugging the engine. Four strokes don't like to be lugged any more than a two stroke. Besides, you wouldn't be able to reach the maximum potential for the boat, engine, prop combination. All three engines can suffer damage from over-reving as well so under propping is just as bad as over propping.

 

[Frank Acampora]

Re: Prop/RPM Question

It is MORE important to prop correctly with a four stroke engine. The four stroke engine only has one power pulse per cylinder for every two revolutions while the two stroke has twice that.

 

[rutcutter]

Re: Prop/RPM Question

You are right Frank and I did not think about that. I appreciate you guys comments.