Trojan Boat Forum

I have an 89 trojan 10.8 m International Sedan (sportfish). 454's
I can find no tags on the velvet drives. How do I determine the gear ratio so I can replace the port trany?

well I figured out a couple of things. the 71-1017's are rated for up to 310hp. the 72-1018's are rated for up to 475hp. I have 350hp so that puts me in the 72-1018's. now for solving the ratio

hi bruce i think one way to figure it out is if you have the tranny out of the boat you can mark the input shaft at say 12:00 and also mark the drive end at the same location-put it into gear and spin one shaft 360 degees and count how many time the other shaft turns. if it spins once you have 1 to 1 and so on. if it goes 1 -1/2 to 1 or 1-3/4 to 1 you can compare it to what was an option for that year or a tranny place can then tell you good luck

That method won't work do to the clutches slipping . The trans needs to spin around 500 to engage the clutches . Now with a photo tach you can do it with the engine ruining compare engine speed to shaft speed , of course a slipping trans will throw you off.

Whats wrong the the trans ? Way not rebuild that one ?

and most likely you do have the 72 sere as

You can tell a 1 to 1 by looking at it no reduction unit on it . But I doubt you have 1 to 1

thanks for info on that prowler didn t take clutches into consideration. good to know though thanks

Thanks for the information. My boat with size, motors, being a sportfish and so forth It comes down to the 1.88 to 1. It also helped that a velvet drive mach happened to show up at the marina.LoL. But he told me my boat (size, motors, style etc.) only came with two choices of trany. Looking at them with no hesitation he said 1.88. it is now stamped on the casing. Again I thank all for the replies. This ole boat has been out of the water for 3.5 years. damn near new everything now and going in the water thursday morning. a few more small things to do over the next few months but its so close now.

thanks again, Bruce

oh yes, what was wrong with the transmission;:::::::: the engine was running at to slow of an idle (300rpm) so the trany rattled, clanked or what ever you want to call it. By raising the idle to 600rpms it slipped in and out with no sound at all. NO REBUILD!!!!!!!!!!!!! After working so hard on the motors I had no desire to pull the trans.....so I got lucky I think.

That's great news.