drive ratio

[jmccall001]

1982 sea ray 260, 5.7, pre alpha sterndrive. How do you learn or compute the drive ratio at the prop.Going to have to replace prop (spun out) and want to do it righty. The boat is a 245 weekender, actually 26 ft long with swim platform, <br />Thanks for the information.

 

[pine island fred]

Re: drive ratio

Can you get to the bolt holding the crankshaft pulley or is it covered by the raw water pump? If you can rotate the crankshaft with a large socket, see how many turns it takes to rotate the prop once. regards fred

 

[Don S]

Re: drive ratio

Look at the port side of the drive on the upper gear housing. It normally has a gear ratio stamped in it.<br />But you should have a 1.50:1 ratio.<br />The gear ratio shouldn't really be a concern if all you want is a new prop.<br />What is the prop part number of your old prop. And what was the WOT rpm you were getting with it.<br />All the calculations in the world only get you close. On the water testing on your boat will give you the answer to which is the proper sized prop.