Tohatsu 90 TLDI

[jshoes52]

I have about 80 hrs on this motor now, and it has been flawless. I have a question about running it. Between about 3000 and 3900 rpm, the motor is noisier than at 4000 or above and 3000 and below. Does that mean I should avoid the noisiest rpm ranges? Is it hurting the engine to run it in that range? It smooths right out above 4k.<br /><br />Thanks

 

[TOHATSU GURU]

Re: Tohatsu 90 TLDI

If you took a DB meter and measured the noise level you would discover that it is louder as you go higher in RPM's. The human ear hears some frequency's of sound much better than others. The particular frequency range on your engine at the "noiser" RPM's is just something that your ear hears better than the frequency's at higher RPM's. It is not hurting the engine, but if you find it bothersome, then avoid it. Just as a side note, four-stroke engines are often perceived as being quieter at some higher RPM's than at some lower RPM ranges. Direct injection engines have sound qualities that are closer to four-stroke engines than older two-stroke designs.