Evinrude 55 HP lower unit interchange

Looking for a replacement lower unit for my 1977 Evinrude 55 HP, drive shaft is 20" to top of pump housing. What year models and HP might be compatible? I see a couple out there, but welcome any others. Already repaired a hairline crack, don't see evidence of leaking but still taking on some water, now gears are popping so I'm assuming prop shaft seal is compromised, possible bearing and/or gear damage making further repair impractical.

Try Tim's Outboard in Hackensack MN 2186822331. Mike Dan or Teresa. They build them for you and advice on interchange. Tell em Tim sent ya. Got one of their units shipped over yesterday.

Where you located? Whats wrong with your old one?

I'm in Danville, east central IL. Had a hairline crack toward the front of the prop shaft (apparently purchased it that way in the spring), fixed that with a grinder and JB Weld. That repair seemed fine, no oil in the water but maybe 8-9 outings on the pontoon later the lower unit started popping sporadically then rhythmically, vibrated the whole boat, especially on acceleration. Limped back to the lift, drained the lower unit and found a couple of ounces of water and the lube was a thick dark ooze and smelled bad. The JB Weld showed no signs of damage, but I figure with that crack (and whatever caused it) further work on the unit might be a waste of time and money. But finding a replacement, rebuilt or otherwise, looks tough for a 1977.