Gear Ratio and RPM measurement on 1989 Evinrude 20HP E20ELCEM?

WriterCJ

Seaman Apprentice
Joined
Aug 17, 2010
Messages
47
Can anyone tell me what gear ratio was used on a 1989 20HP Evinrude (E20ELCEM)?

Have a slightly damaged prop after an unfortunate encounter with the bottom (think I hit a disused mooring with no marker buoy at low tide :( ). Before I order a new prop I want to check that the existing size / pitch (10" diameter X 13" pitch) is right for my boat (17ft fibreglass planing hull with cabin -- weight currently unknown but will get it weighed when I pull the boat out of the water in a few weeks).

With current prop, and just me on board (about 234lb) the boat gets up on plane at around 8kt and cruises at 16kt at WOT. With wife and kids aboard too it just about planes and levels off at around 10kt at WOT.

Also, if there's no tachometer fitted how can I check RPM at WOT? Sorry if this is a silly question. Can you get a portable / hand-held tachometer and attach it to the engine to measure RPM?

Cheers,

Calvin!
 

Bob_VT

Moderator & Unofficial iBoats Historian
Staff member
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May 19, 2001
Messages
26,019
Re: Gear Ratio and RPM measurement on 1989 Evinrude 20HP E20ELCEM?

Sounds about right for a 20 HP in a fiberglass boat.

Look on ebay or on the internet for a "Tiny Tach" which is used by many with smaller outboards.
 

WriterCJ

Seaman Apprentice
Joined
Aug 17, 2010
Messages
47
Re: Gear Ratio and RPM measurement on 1989 Evinrude 20HP E20ELCEM?

Thanks Bob... will check out the "Tiny Tach".

My first outboard... so much to learn :).

Cheers,

Calvin!
 

WriterCJ

Seaman Apprentice
Joined
Aug 17, 2010
Messages
47
Re: Gear Ratio and RPM measurement on 1989 Evinrude 20HP E20ELCEM?

Anyone used one of these laser / optical tacho's successfully on an outboard?

I'll only use the tacho very occasionally, so looking for the most economical option.

Looks like you just put a piece of reflective tape on the rotating part you want to measure (the flywheel?), then point the device at it.
 

WriterCJ

Seaman Apprentice
Joined
Aug 17, 2010
Messages
47
Re: Gear Ratio and RPM measurement on 1989 Evinrude 20HP E20ELCEM?

Gear ratio update -- think the gear ratio on the E20ELCEM is 2.15:1 -- found that info on a prop manufacturer's website... but will try and verify it elsewhere.
 
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