mercon III to 5w20?

[R-mallis]

has anyone changed out there trans fluid with 5w20 oil to get rid of that high pitch whining noise? i have a 1990 sport and i was just wondering if thsi would be a good idea.

[nms1991]

R-mallis the whinning noise will not go comletly awy it is due to using straight cut gears in the reduction part of the trans. Pcm used straight 20w oil in that year of trans to try to quiet them down. You could also have a Pcm trained service tech try to readjust the gears by reshimming the gears or replacing the gears with new ones. But otherwise it is normal noise comming from the trans of that vintage of boat, ihave seen some boats with over 1500 hours with no problem from motor or tran except normal matenance.

[tryan]

mercon and other atf's have anti-foaming additives. 'oil' does not.

if you do change fluid types, it is possible to develop leaks unless you put in new seals and do a complete flush.

my advice would be to run what's in there.

[R-mallis]

thanks for the advise guys i think ill just put up with the noise