props and gear ratio

[Bruce Colley]

purchased a 1989 searay amberjack 270 twin 4.3 ho, I am going to assume with alpha 1 gen 2 legs as that is what i believe they came with. It didn't come with props so i am, trying to source some out. my first twin engine boat. I am assuming one leg is counter rotating. Questions are how can i tell the gear ratio, Any suggestions on pitch and props, and is the counter rotating leg does it take a special prop. I assume the port engine turns clockwise and the starboard engine turns counter clockwise.

 

[scoflaw]

The PO has no info for you ? A lot can change over 30 years, probably a good idea to pull the drives for a look/see anyways. While there off you can rotate the drive shaft while observing the prop shaft to determine gear ratio. If the engines start it will be obvious which drive is the CCW.

 

[Lazy Daze]

In addition to the above, Sea Ray also has a Prop Matrix on their website that would show the various ratios and props for every boat. I believe it's under "Owner's Resources" somewhere. If you post the engine serial numbers, I may be able to tell your ratios.

 

[Bruce Colley]

thanks for the help, it has new engines so those wont help, is there a way to find out using the boat serial number what the original boat came with.

 

[Lazy Daze]

Did you look at the prop matrix on SR's website?

Do you have the drive or transom serial number?

 

[Bruce Colley]

I just looked it up what I thought alpha one, 1.84 was the standard gear ratio, and I found the stock prop pitch and size . I didn’t know about that resource until now