tiny tach on 30 hp 4 stroke tohatsu

[hipster dufus]

am thinking about putting one of these on the new rig. i am concerned about the firing of the spark. does this engine fire once every 360 deg or twice? the tach is adjustable. thanks

 

[Midnight Krawler]

Re: tiny tach on 30 hp 4 stroke tohatsu

On a 4 stroke engine a cylinder will fire every 720 deg and a 2 stroke will fire every 360 deg.

 

[pvanv]

Re: tiny tach on 30 hp 4 stroke tohatsu

The 3-cylinder motor has a piston come up to TDC every 120 degrees (both on compression and exhaust). Each individual cylinder has its power stroke every 720 degrees, as MK noted, staggered 120 degrees apart. If you have any sort of dash board, I would suggest the factory tach, as it won't get a dead battery in a couple of years, and reads very reliably and accurately. OTOH, if you just want to dial-in the best prop, and then pull the tach off, a tiny tach is OK. Some of the induction tachs have troubles due to the very high energy of the 3-cylinder CD, and can occasionally get confused, giving "impossible" RPM readings. The trigger-wire routing is very important on induction tachs, to reduce that "confusion". But... One nice feature of some of the induction tachs is that they may have an integral hour meter -- handy for determining service intervals.

 

[hipster dufus]

Re: tiny tach on 30 hp 4 stroke tohatsu

no dash board. i really like the hour meter on this tach for maint intervals. on the order form they ask for engine info in case they do have to put a filter on it. i had one on my 9.8 and it did not work well because of the spark firing order. u can reset this one to read once every 360 or at 180. will it be good enough for break in procedure and prop dial in? after that i will use it for maint intervals. thanks

 

[Sea Rider]

Re: tiny tach on 30 hp 4 stroke tohatsu

Using a TT will definitely be good for break in, max rpm at wot, prop selection, gear, engine oil changes, track of parts hour change, maintenance intervals and total engine meterd worked hours. Set at 360? should work ok, 180? are for 2 strokes Tohatsu engines.

Happy Boating

 

[Barnacle_Bill]

Re: tiny tach on 30 hp 4 stroke tohatsu

You need to check with TT for your setting. Many 4 strokes now have what is called a waste spark.

 

[hipster dufus]

Re: tiny tach on 30 hp 4 stroke tohatsu

got the tach, it has total hours, resetable hours and can be set for any firing order. so the 30 ho fires once per revolution right. if it sparks more than that i can set the tach up for that. like i said i will use it for maint and break in along with prop selection. unfortunately i have to wait another month for the new boat and motor.