Help with outdrive

I have a Mercrusier 140 inbord/outbord.My question is with the seriel # gone from lower unit,how do I tell what size unit I have?With a 3.0 liter eng. I would think it's a Bravo 1,or can I goo off of the size of the hub nut?

A 140 I/O will have an Alpha Drive. The year will determine if it is a Generation two or not. Usually a 3.0 ltr has a 1.98:1 ratio.

Thanks Dockside...

How difficult is it the change out the water pump inside the lower unit?Think that will be a task to be tackled before I leave on the 12

It can be done easily. Just take your time. Do you have a service manual? And what year is your boat?

No not yet.The hull is a 77 mdl. in very good shape,got it from my uncle I think the mtr and drive unit are 99. He just had the mtr. put in before the summer and the unit serviced before last winter.

Looking at the drive, do the upper and lower have nuts and bolts holding them together or nuts with studs?

It has 6 studs with bolts.Mdl.# 6014644

Ran the mtr.this morn.in driveway,@idle apx.650-700 rpm.oil pressure is 30-35 lbs. water temp.is 140.ran for about 10 min.or so,then ran rpm's up to about 2,300 oil pressure is at 40 lbs. and temp. went to 160,then dropped to 140. When I put unit in gear and run rpm's up to 1,700 tempdrops to 135 and oil is at 140.What makes me think the raw water impeller may need to be changed is when I was out in it Sunday under a load the temp. hit 200 plus and the mtr. had alot of ratteling going on.I think it was just cheap gas in so far as the valves knocking.