Damage assessment and Drive ratio and type

[Darth]

I just lost one of my drives and believe it is in the lower unit only (but haven't taken it apart yet). Just cruising along, the Starboard drive made a nasty noise and I shut it down to look at it. Seeing no obvious damage, I tried to restart the engine and it was locked up. Trying to restart a number of times, all of a sudden, it started but made grinding noises, so I immediately shut it down again, and made it home on the Port engine. With engine off, the prop turns freely in both directions in neutral. In forward, it locks up in forward direction and turns with normal clicking noise backwards. In reverse it locks up in the reverse direction and turns with nasty noises in the other direction.

If I have to replace the complete drive or just the lower unit, I want to make sure I am getting the right type (SE 106?) and the right ratio. My boat is a 1983 Sea Ray 260 Sundancer. The power is two 470 Mercruisers (4 Cyl). My Operation and Maintenance Manual says they are 1.84 Ratio, but the SN tags are both unreadable, and my "Mercruiser MCM 470 Installation Manual" gives prop selections for both 1.65 and 1.84 ratios. Being a twin, it is obvious that the two ratios be the same.

BTW, would there be any advantage (Since I have to change at least the lower unit) to making one of them a Counter Rotation. The boat steers straight now with no problem and the trim tabs are pointed pretty much straight ahead.

[Tech Support]

It sounds as though the problem is in the lower unit. You should go ahead and check the upper unit by removing the top cap and inspecting the gears for signs of excessive wear or heat. Your drives should be the 1.84 ratio. You can verify that by counting the teeth on the upper gears. They should be 17 & 19 tooth gears. If you only need a lower the ratio of the upper does not matter. If your boat steers fine now I would stay with a standard rotation lower. If you do need a new upper you need to measure the input shaft to see if you have the old style shaft. The old style measures 8 1/8" length while the new style is 9 9/16" long.

Tech Support

[Darth]

It sounds as though the problem is in the lower unit. You should go ahead and check the upper unit by removing the top cap and inspecting the gears for signs of excessive wear or heat. Your drives should be the 1.84 ratio. You can verify that by counting the teeth on the upper gears. They should be 17 & 19 tooth gears. If you only need a lower the ratio of the upper does not matter. If your boat steers fine now I would stay with a standard rotation lower. If you do need a new upper you need to measure the input shaft to see if you have the old style shaft. The old style measures 8 1/8" length while the new style is 9 9/16" long.

Tech Support

I pulled the top cap and the upper driveshaft bearing was completely gone with the upper gears broken up. So I guess I am going to need the upper unit after all. I'll have to wait to order until I pull the unit to check the input shaft length as you suggest. At that time I can check to see if the lower unit appears O.K.

This is taking time, as I am attempting to do this with the boat on a "hydro hoist" lift while I am floating on a 4' x 8' piece of styrofoam. Luckily, I have pulled the drives before, so I think I can handle it by pulling the lower unit off first and then the upper unit (tied to a rope of course). Our lake level is so high from all the rain that my mud "ramp" is totally under water.

Whee! Aren't boats fun?

[Technical Support]

Also, if you do decide to switch to a counter rotation, you should check the helm control to make sure that you can throw the cable the opposite direction. Some helms will only work with a standard rotation.

Tech Support