what type transmission fluid?

I'd like to add that our past marine transmission specialist Eric from FFM also warned about using synthetic. He said it was too slippery. Regular non synthetic works. Also, being on a SS budget and a covid furlough from part time employment, I can't see playing the higher cost especially that purple bling stuff JQ is always pushing. I think he has stock in the company!

Maybe to put it a little differently

You won't go wrong with any fluid with a Dexron 3 or Dex/Merc rating.

Notice the distinct lack of any mention of whether it should be dino oil or synthetic oil.

It has to meet the same specs whether it's synthetic or dino stuff.

Plenty of people swear by either.

Is synthetic necessary?..................No , but it won't kill your transmission based on the number of people that use it with no problems

Your tag on your 90 may say to use 20 weight engine oil but that's changed over the years.

PCM couldn't make up their mind in the early years of the PCM transmission.

Maybe somebody will tell you that synthetic is too "slippery" but all those people using synthetic for a whole lot of years now seems to have disproven that reasoning.

With that said..............you can make your own decision   

proc wrote: what type trans fluid should i use in 1990 sport nautique 1.23 pcm ? thanks

I have a '93 with a PCM 1.23 and use Valvoline ATF Dex/Merc for vehicles requiring Dexron III .
Do not use synthetic.