portable Tach - alternatives to tiny tach? Maybe timing Light?

[BF]

Hi,

I got a new 25 hp EFI 4 stroke merc to break in this spring, and want to be able to check WOT rpm's when the time comes. It's a tiller steer, going on an open utility boat, so I'm not sure I want to bother to fit a permanent tach in there. I know tiny tach has a following on here, and I checked them out on-line.... I don't like the non-replaceable battery, and that it'll probably only use it a couple times. I'm just wondering what alternatives there are... How about an automotive timing light with a tach function? Should do the trick, shouldn't it (?) Can they be switched between 2stroke and 4stroke? If not, they would read double rpm's when connected to a 2 stroke, right? (BTW, yes I said this motor is a 4 stroke, but I'm thinking about whether I can use it on my other small motors too)

Also, correct me if I'm wrong, for rpm's taken off an timing light, there shouldn't be any setting based on the number of cylinders... right? All it knows is that for a 4 stroke, the actual rpm's is twice the rate that spark is being sent to that particular cylinder... right (?).

Does anyone has a timing light with tach that reads correctly both 2 and 4 strokes (settable for 2/4 stroke). One concern is that if they only read the correct rpm for 4 strokes, that when attached to a 2 stroke it will be out of range (at 12K rpm), when running at WOT (actually 6000 rpm).

Thanks for your $.02

 

[Scaaty]

Re: portable Tach - alternatives to tiny tach? Maybe timing Light?

I got an digital "Actron" off Ebay for about $70. All the bells and whistles. Like any other timing light, it counts the spark off any plug wire (don't need to be #1 if just a tach reading)
Just need a 12 volt battery to run it. And set it to Tach. Thats it..half the reading for 2 strokes
I'm not sure about the 12k rpm though. Some smaller Honda 600 bikes twist over 16,000, and it being digital, probably goes way over that. Have to check the specs when ordering ...

 

[Mike722]

Re: portable Tach - alternatives to tiny tach? Maybe timing Light?

I have one that is made for testing hand held power equipment. Mine was made by Echo. It is wireless or has a spark plug wire lead clamp. I assume it has a changable battery, but I have had it for 10 years and it still working.

 

[deejaycee_2000]

Re: portable Tach - alternatives to tiny tach? Maybe timing Light?

quicksilver makes a small digital tach, and stihl have one that works great (they use it on chain saws)

 

[BillP]

Re: portable Tach - alternatives to tiny tach? Maybe timing Light?

To check motors without tachs I use a handheld type made for rc model planes. It's about the size of a cigg pak and runs on self contained batts. It's made for 2 or 3 blade props. To use on ob motors I take the motor hood off and place masking tape across the flywheel...it duplicates a 2 blade prop. Hold the tack and aim down at the flywheel. I also use it to check other tachs...it even worked on my full size plane when sitting in the cockpit and pointing though the windshield. Cost is around $20-$25 and they are very accurate. Calibration is done by aiming at a lightbulb. Mine came from Tower Hobbies. It's about 18yrs old and still working.

bp