tranny gear ratio

Go with the ratio and prop diameter that was in the Prostar originally. The ratio has already been matched to the hull. The pitch of the prop may change if the HP of the engine is different than the original.

kapla wrote: And that would be a 1:1 ?

Sorry Seb. That's a question to post on a MC site!

It came with either a 1:1 or a 1.52:1, the prop shaft is either 1 or 1-1/8 respectively. You need to use one of those two transmissions or your in a world of hurt for prop selection and mounts that will fit original holes. If you change from one to the other you need a new strut, prop, coupling, packing log, etc. You would get slightly better holeshot and whatnot with the 1.52:1.

The 1.23:1 trans would have you with a prop that turns opposite of what came on the boat and most likely needing more expensive or at least harder to find custom parts.

Like pete I am assuming your friends are using the same hull, if they are starting from scratch and just pulling gear off the MC then as Chris recommends I would probably use the 1.23 to 1.

They are coming out of a bare hull so they have to buy everything new no parts to recycle.

79nautique wrote: since it is a GM 5.7 and a volvo motor I doubt it is reverse rotation so there wouldn't be any issue with using the 1.23:1, and it is my understanding that the down angle of the tranny is the same as if it was a 1:1 so I'm really missing where any parts need changed oh well what do I know. After all wasn't the 1.23:1 tranny designed to replace the 1:1 so that it maintained the same shaft angle but leveled the motor, Oh Well you guys are the know it all's anyway, too bad it's not always right.

Personally, I would tend to take Joe's word on whats involved with a 1.23 tranny swap since he's working on that project this spring, rather than resort to BS speculation and namecalling.

79nautique wrote: JoeinNY wrote: The 1.23:1 trans would have you with a prop that turns opposite of what came on the boat and most likely needing more expensive or at least harder to find custom parts. Like pete I am assuming your friends are using the same hull, if they are starting from scratch and just pulling gear off the MC then as Chris recommends I would probably use the 1.23 to 1. since it is a GM 5.7 and a volvo motor I doubt it is reverse rotation so there wouldn't be any issue with using the 1.23:1, and it is my understanding that the down angle of the tranny is the same as if it was a 1:1 so I'm really missing where any parts need changed oh well what do I know. After all wasn't the 1.23:1 tranny designed to replace the 1:1 so that it maintained the same shaft angle but leveled the motor, Oh Well you guys are the know it all's anyway, too bad it's not always right.

I stand by my previous statement, because I also assume its not a reverse rotation motor. I say they wouldnt want to use the 1.23 because it would give them a RH prop and that boat came with a LH prop. So now you change the rotation and put in a ratio that also wasnt available it opens a can of worms. I don't know much about mastercrafts but I have experience trading motor rotations, prop rotation, and transmissions.   I believe this guy would end up with one of a kind parts, its only a question of how many, and none of his parts are going to come off a mastercraft list.

As to the info on shaft angle its not relevent, except in that by making the motor level he might also need a new engine box as well since that happens by lifting up the transmission and rear of the engine significantly.
   For general knowledge of those considering it swapping a 1:23:1 for a 1:1 requires complete new rear mounts (that adjust higher), new engine attachment blocks in the front, new damper plate (different input splines), new driveshaft (51 vs 54 inches), and an appropriate prop.

Don't see an issue with the prop plenty selections to choose from 1, 1-1/8 w and w/o spline, so that's a moot point, might be a little expensive shipping it though. So if availibilty in Argentina is and issue then the prop's availible there needs to drive the decision.

for the dampener plate well why are you re-using an old one to start with? guess you just like tearing things back apart later after it fails befor eeverythink else. Don't understand why a new one would not be installed from the get go, again availiblity is not an issue no custom stuff needed but again local availibilty might be an issue.

for the shaft, well odds are your going to need a new one regardless unless you use the exact same set-up that was in it, or if a shorter one is required then the old one can be reworked and a new couple made to mate with the tranny's coupling. But again it's most likely all ready there and matched to the logs and strut so the question gets to be is the right length, and if not is it to short for the application where a new one is required. After all they don't last for ever and if your going to do all of the other stuff then why not buy a new one to start with.

Good point about the higher mounts but again easy fix, plenty of ways around that with out spending money if the stuff is all ready laying around the garage floor or bought fairly cheaply.

so I'm really not seeing all the problems, you act like they never ever had a 350 hooked to a 1.23:1 tranny before, which we all know isn't true, so picking the correct prop should be pretty simple might need to tweek it a little playing with the cup to get the rpms where they need to be, but oh well what do I know.

JoeinNY wrote: It obviously can be done but its more difficult and gives you a prop that doesnt turn the way the boat came with, so the upside over going with one of the original setups is?

STARTING WITH A PS190 HULL did you catch that, so do they have a shaft, do they have a prop? they didn't say..... so if your buying new big deal if it's not a stock set up.. you can get the right pitched, correct rotation prop be it RH or LH easily. You got to position the motor anyway as I'm sure they're not using the mounts from the volvo maybe they are, regards less they still have to get them for the tranny or use what is on the tranny all ready.

So again let's just say oh go with the orignal set-up not that they will be able to get the pieces since they're over sea's and it would be easier to get stuff locally rather than shipped, oh well just don't agree with the BS your feeding them scaring them and bring up minor stuff, cause if you have to build from a manual or a drawing then you better not start this type of project, but to me seems real simple stuff but I don't use drawings or manuals to fix stuff either.

F-IT, hang an outboard on the back of it, South of the border it wouldnt be out of place