89 -120 vs 85-140

[tony120]

just repowered with a fresh 140.the boat did 34mph acording to my gps with the 120 with a 13-19 ss prop at around 5 grand. the rebuilder told me that an 85 140 looper is a small bore.the 89 was a large bore 120. the 140 came with a 15-17 aluminum prop. looking at the prop on both,the 140 is huge.just a question without opening too many cans of worms..gaining 20 more hp do you think I'll break 40mph?

 

[DJ]

Re: 89 -120 vs 85-140

tony120,<br /><br />Regardless of what engine you have 5K rpm is too low for that engine, with a moderate load. Prop it to run around 5800 and it will perform MUCH better.

 

[Dhadley]

Re: 89 -120 vs 85-140

They both make about the same amount of torque. The 89 will make slightly more. The 85 uses a V6 size lower unit that requires a V6 style prop, therefore the larger diameter and the reason they dont interchange. The gear ratio is slightly different. <br /><br />As DJ said, 5K is way too low. I would heed his suggestion and shoot for 5800 or more with an average load.<br /><br />Good luck!

 

[tony120]

Re: 89 -120 vs 85-140

thanks guys.i didnt think the props would interchange.I'll see where the rpms are when the weather breaks and shoot for 5800.keep ya posted,thanks