Compatible lower unit for 1977 johnson 70hp

Hey everyone, so I made an oopsie this weekend and hate myself for it.. I was out Friday evening and was out exploring when I ended up in a channel, which I usually always try to avoid channels especially with this motor since I try to baby it... went through no problem but on the way back I smacked what I assume was a rock since I couldn't see anything under the water at about 1/2 throttle, It caused the motor to pop the trim lock and fly up... Instant regret, I checked the motor best I could and didn't see anything so drove back to shore at about 1/2 throttle and meant to check it the next day but forgot and got back on the water... Half way through the day cruising along and bang engine instantly shuts off and I couldn't get it out of gear had to fight with it and then couldn't even turn the flywheel. So I got towed home and noticed the Crack on the lower unit so I assume it puked out all the gear case oil and then self destructed, I pulled the lower unit off and found lots of metal shavings, the motor seems fine though... So I have a 85hp that's also around a 77 year, can I put that lower unit on for now and see if I can fix this one later on? Kind of tight with money right now and would like to be able to finish this year off.

There is ZERO chance that an 85 HP 4 cylinder lower unit fits !!!-----Just can not be done.

racerone said:

There is ZERO chance that an 85 HP 4 cylinder lower unit fits !!!-----Just can not be done.

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Okay, I wasn't sure, some people said yes some said no, and to me it looked the same so I wasn't sure.

Absolute ZERO chance it will bolt on !!----Splines on top of driveshaft are totally different !!----Other differences as well.

Ok so abandoning the thought of swapping lower units I put in some elbow grease, pulled the 85 out of its hibernation gave the engine a deep clean and the carbs a quick cleaning and it fired up... So figuring I had nothing to lose but "MPG" since I hear the V4's are kind of pigs on gas.. I swapped motors and took the boat to the lake today... the 85 V4 sure is more stout, gets up on plane quicker and holds it much better, especially at slower speeds and in corners. I still have some bugs to work out (small bog here and there) but it ran pretty decent. Now figuring I had 15 more H.P I figured just like anything it should be quicker, even just by a few Kmh.. Nope, it's about the same top speed sometimes actually slower, I tried every trim setting on that 70 and the fastest I got it going was about 54.5kmh, usually averaged about 50-52 though. Today with the 85 like I said holeshot was quicker, holding speed was alot better, but top end I got (once again tried every trim setting) was 51kmh... Why isn't it quicker? I noticed the prop is alot smaller though (without technical measurments) the 85 prop is about 3-3/8"s from the hub to the end of the blade on each blade, and somewhere around 9-3/4 tip of one blade to the tip of another (all measured at the widest parts) my 70hp prop is a fair bit bigger, don't remember each blade length but from one blade tip to another its around 12-7/8" or so. Are these both stock to these motors? Can I switch the prop from the 70 to the 85 and maybe gain a bit more speed? I mean if I'm adding more weight and burning more fuel I'd like to atleast keep the same top end... Preferably gain more... I know on my old 14' aluminum I went from a 9.9 to a 15 and my speed almost doubled... I don't expect the same results here but I did expect some gain in speed.