Tohatsu 90 (2-str) whine

[al40]

Got a new (had been lying in stock since end of 06) Tohatsu 90 2-st at the start of the year. I noticied after a few hours that there was a distinct "whine" to it, especially around the 4000 rpm mark. Sounds like the whine you get off a turbo. I reported this to Tohatsu who took it back and effectively re-built the engine but the whine is still there... Tohatsu have put it down to noise from air intake ports but I'm not convinced!

So any of you Tohatsu 90 owners out there got this problem? It seems to vanish above about 4300 but is really quite bad in the 3800 to 4100 rpm range. There is one speed where it's actually uncomfortable to listen to!

I can't run it with the cover off as every time I come off the plane (no matter how slowly I do it), there is a chunk of water gets thrown onto the back of the case (turning at the right moment doesn't help either)!

Thanks!

[Jizm]

any possbility you can run it in a test tank?

[codprawn]

Try removing or adding an air filter - may change the noise - something like a K+N or even a bit of foam cable tied on.

[al40]

Originally Posted by Jizm

any possbility you can run it in a test tank?

The Tohatsu guys did this for 4 hours at varying rev's after they re-built the engine. I assume this was just to remove any "boat influence" from the equation? I don't have access to a test tank locally unfortunately.

[al40]

Originally Posted by codprawn

Try removing or adding an air filter - may change the noise - something like a K+N or even a bit of foam cable tied on.

Yeah that's a good idea! I guess also removing the air filter altogether for a quick test would determine if that's where the noise was coming from..

[codprawn]

Got to be better than running it with the cowl off!!!