Replacing outdrive.

[deputydog21]

I have a 2002 Bayliner 215 with a Mercruiser Thunderbolt 5.0 motor (305 CID) thats supposed to be putting out 220 Hp with WOT of 4400-4800... It came with a Alpha 1 Gen 2 1.47 outdrive and a 20 pitch 4 blade prop. I currently have the outdrive off for some work and am working on fixing the boat up over the winter. The boat is a dog in the water, has a decent hole shot but no top end and poor gas usage when cruising. I have found alot of other similar motors from better boatmakers that have a 1.62 geared outdrive. Would I benefit from changing outdrives to a 1.62? Just looking for overall performance and is possible better gas mileage.

 

[stonyloam]

start With the basics, that is the prop. Take it out and do a WOT run and record the speed (GPS if you can) and engine rpm. From that info should be able to determine how to proceed. If you have a good hole shot and low top speed you may want to go to a higher pitch prop, and maybe a three blade. Changing the prop is by far the easiest and cheapest way to go.

 

[Scott Danforth]

First, welcome aboard

I have a 2002 Bayliner 215 with a Mercruiser Thunderbolt 5.0 motor (305 CID) thats supposed to be putting out 220 Hp with WOT of 4400-4800... It came with a Alpha 1 Gen 2 1.47 outdrive and a 20 pitch 4 blade prop..

way too much prop. 15x19P on that motor with that boat and the 1.62:1 drive. with the 1.47 drive, you should be in the 15x17p range. your motor should be hitting WOT RPM. my guess with the prop you have on your boat you cant hit anything over 3800 RPM which is way over-propped.

The boat is a dog in the water, has a decent hole shot but no top end and poor gas usage when cruising. I have found alot of other similar motors from better boatmakers that have a 1.62 geared outdrive. Would I benefit from changing outdrives to a 1.62?

no need to change outdrive. simply put the right prop on the boat for your application

Just looking for overall performance and is possible better gas mileage.

the two are mutually exclusive. fuel economy and power boating are a dichotomy. if you want fuel economy, get a boat with slaves pulling on oars or a sail boat.

 

[achris]

And the tacho needs to be a shop tacho, not the one in the dash. Not accurate enough.