Tacho readings

[puddlesplasher]

Hi all,

I recently discussed an issue about my tacho. Having sourced and fitted a new one I tested it out today on muffs. Ensuring that I had an adequate flow of water at all times from the pee-hole the revs went beyond 4500 before I *pood* myself with shock that it wasnt even at full revs. Considering that the other tacho only read 3300 at WOT.

Therefore on that note is it possible that a tacho will read higher revs with muffs as there is no water resistance against the prop? If so I presume that in the water the revs will indeed drop and again if so. Then what size of prop would give me more revs and hence more speed or is it less revs, bigger prop etc...

Please keep this very simple as I am not mechanically minded when it comes to the variety of prop measurements, turns, distances between blades, pitch etc.....

Many thanks.

 

[Chris1956]

Re: Tacho readings

That motor will rev up very high with no load on it. It will also destroy itself if you continue to give it high RPM without a load.

Dont run it faster than 2000RPM without a load on it. The best thing to do now is take it out on the water and see what the max RPM you can get out of it with a normal load. You want to achieve 5000RPM or so. If the Tach reads less at full speed, decease pitch of the prop (new prop). If the max RPM reads mor ethan 5K, increase Pitch of the prop. Each size of prop difference adds or subtracts about 400RPM from motor speed.

 

[puddlesplasher]

Re: Tacho readings

Well done Chris on excellent simple advice.

The high revs was a one-off.