How to find correct prop specs?

[wormboy]

I am worried that I am "over-propped" on my 1989 Evinrude 150, because of low WOT rpm readings. I am trying to borrow a hand-held tach or timing light w/tach to check my tach reading (is there any problem with using an automotive one with the CDI ignition?), but was wondering how someone determines what propeller is appropriate for the boat and motor to get the approp WOT rpm range? Is there a chart somewhere or website? The motor is an E150STLCEM on an 18.5 ft center console w/ max load of 2000 lbs-- i use it mostly for freshwater fishing for lake stripers, but also pull the kids on a tube with it sometimes. Any advice is greatly appreciated!
Also-- in case the loaner tach doesn't show, is there a way of checking the tach with a voltmeter or multimeter to see if it is operating correctly?
Thanks!!8)

 

[AlanR]

Re: How to find correct prop specs?

What prop you got on there now? I could guess a 16 or 17 would do you good but like a 21 would be to tall

 

[JB]

Re: How to find correct prop specs?

Wormboy,

Please repost your question in the Prop Forum.

 

[wormboy]

Re: How to find correct prop specs?

Thanks for the reply Alan-- I'll check it out tonight and get back to you; it should be stamped on the prop somewhere, correct? In any case, where can someone look up this info, i.e., what pitch and diameter is appropriate for top rpm for a particular boat configuration? It would seem odd to have to try different props to get to the correct rpm by trial and error--- not to mention expensive if they don't allow returns on the prop!!