Inspecting Lower Unit For Problems

[fmjnax]

I am currently restoring an old bass boat. It had been sitting in a field completely untouched for at least 4 years (and unknown how long, if any, before that). The outboard is an '87 90hp v4 crossflow (J90TLCUR). I am rebuilding the powerhead due to low compression in 2 out of 4 cylinders with some scoring.

I want to check out the lower unit to determine what needs to be done. The water pump (entire kit) for sure is getting replaced. I THINK the gears themselves are fine, but throwing this out to the group to see if there is anything I might be missing. When I cracked open the drain plugs, I was glad to see it still full of gear lube and it came out clean without any water. Not milky at all and no water after the oil. The magnet on the bottom plug was free of any metal at all.

The LU shifts between F-N-R well enough. When turning the driveshaft CW by hand, the prop shaft spins CCW in F, not at all in N (spins freely), and CW in R (I might have the F/R backward as I can't recall which-is-which with the shift lever up/down). I took a look at the propshaft seals and the seals under the water pump and they seem fine to me.

I've rebuilt a couple of LU in the past and I'm not seeing any signs of issues I had with those units so my untrained opinion is that the gears are most likely fine. Is there anything else I can do to confirm?

 

[racerone]

When draining a lower unit the water would come out first if there was any in there.----Pop out the bearing housing below the water pump.----The thrust bearing there is a very good indicator of conditions.

 

[Faztbullet]

You rebuilding or refreshing motor?

 

[rowerowe101]

pressure test gear box 15 psi

 

[Faztbullet]

Pressure and vac test lower...

 

[fmjnax]

Sorry, I didn't get much time to check on this due to work but finally got around to it last night. I don't have a pressure tester but I do have a vac pump. I couldn't get it to hold any vac at all. However, I was already going to replace the upper and lower oil seals with the water pump just for relatively cheap piece of mind.My apologies for not stating that in the original post and being more clear. I was more seeking advice on checking the deep internals without fully disassembling it.

As for the question about rebuild vs refresh, I'm doing both I suppose. I am completely replacing the powerhead (undressed). I have already rebuilt the starter and carbs. I will be rewiring all of the electrical. All new hoses, etc. I'll cleanup/replace anything else as needed. As for the midsection, the tilt/trim was working when I pulled the OB off of the hull so I'm not anticipating anything needed there, but will also refresh that section as needed. LU is the same. Clean what needs to be cleaned. Replace what needs to be replaced. Fresh coat of paint, reassemble, and hang her back on the hull.