Tach for Small Outboard

[cheddar 86]

I have a 20hp Yamaha 4-stroke Outboard. I would like to find a cheap method to verifying idle rpm. I've looked online for tachs and find that there are $40-50 options available - Tiny-Tach, Sendec, ENM. My hesitation is that I've read in multiple places that Outboards generate more engine noise, but I don't know if that is problematic in my case. Some of the reviews of aforementioned products state that they get weird or incorrect readings - which may be due to number of cylinders or possibly electrical noise. I don't trust return policies for electronics and the hassle of doing so.

Anyone have an actual successful experience doing this - and if so what specific tach did you buy?

[kerryd15]

I went to the Tiny tack HSOforum and ordered direct. Describe what you are using it for and they will custom build one for you. I have a side consel and wanted longer lead and they put a filter diode in it for noise. Think it was $70 delivered. Works real well. Wanted to use it for setting idle and max RPM for prop. Has an hour meter on it as well for oil changes and maintenance.

[311Hemi]

This is what I ordered and have used on my Yamaha 20hp 4-stroke to check RPM's. It just wraps around a plug wire. I have also used in my my snowblower and some other engines. It works great. I just needed a tach to check various motors and was not concerned with oil changes since that occurs once a year on most of my small engines.

"Hardline Products HR-8061 Hour/Tach Meter"

Automotive; $33.06

Sold by: Amazon.com

[cheddar 86]

Thanks for the info...

When you check rpm did you check idle....and was it accurate? (mine is around 1175 rpm @ idle after 10 minute warmup)

[311Hemi]

I actually have an F25, not an F20 so my idle RPM's are a little different than what yours will be.

I think mine may have been a little low....875? I don't remember for sure. I was more concerned about testing a new prop to get as close to 6000 as I could.

Spec on min is: 950 +-50 rpms. I tried to get it right at 900, but it does bounce a little on the tach if I remember correctly.

[kerryd15]

When I read the manual my merc idle is set with a warm engine, in forward gear, and has to be in the water for the resistance or basically not by the hydrant with ear muffs.