1979 55HP lower unit removal

Hi all,

As i managed to get no where with my 1978 55hp i managed to pick up a 1979 evinrude 55hp and am in the process of trying to replace its impeller. however i seem to be stuck. after all 4 of the outer bolts sheared off. I managed to get the one in the trim plate out and the one behind it however i can not get the two bits to seperate at all. no gap what so ever. I cant see any more bolts anywhere. none under the trim plate.

Is there any tricks to getting it off? I need to remove it now as i need to drill out and re-tap the 4 outer bolts that the heads sheared off on. Can i hit the two units in any place with a hammer and not damage it? have ordered a dead blow hammer to do so as i dont think i want to try it with my ball pein hammers.

Mat

Also can i replace the snapped bolts with these? https://www.a2stainless.co.uk/7-16-UNC-x-3-Hex-Bolt_A133TO.aspx think they are the same size. imperial sized bolts are not the easiest to find in the UK, its all metric. gonna be fun finding a drill and tap!

Those four broken bolts are the problem. They are acting like four huge nails. I wish I could give you some advice on getting them loose. The very last thing I would do is beat on it with a hammer. That just isn't going to work and probably will break something. The right way would have been to heat them and not break them in the first place. Too late for that now.

fdrgator said:

Those four broken bolts are the problem. They are acting like four huge nails. I wish I could give you some advice on getting them loose. The very last thing I would do is beat on it with a hammer. That just isn't going to work and probably will break something. The right way would have been to heat them and not break them in the first place. Too late for that now.

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Totally agree with you there. unfortunately they snapped with very little force even with heat. dont think they had ever been removed since it was built. they snapped off just below the surface so maybe half way down the hole. dont think i can even get a drill in there with the lower on seems i have zero luck with outboards.

the lower does not even remotely feel loose. its as if its still bolted on.

This will cause some damage, but fortunately not terminal. Take a chisel and grind it very thin and sharp, like a knife. Then drive it into the seam where the parts meet near rhe broken bolts. You will have to do just a bit at a time, since there are four of them. Yes, it will leak when you get done, but any water that leaks out there was headed back to the sea anyway. If you bugger it up unreasonably, you can repair the damage with welding or epoxy.

BTW, this isn't holding it, but you did disconnect the shift rod, right?

fdrgator said:

This will cause some damage, but fortunately not terminal. Take a chisel and grind it very thin and sharp, like a knife. Then drive it into the seam where the parts meet near rhe broken bolts. You will have to do just a bit at a time, since there are four of them. Yes, it will leak when you get done, but any water that leaks out there was headed back to the sea anyway. If you bugger it up unreasonably, you can repair the damage with welding or epoxy.

BTW, this isn't holding it, but you did disconnect the shift rod, right?

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Thanks yes shift rod is disconnected, I did the pump on a 1978 model so was aware of how it comes apart just this one seems to be stuck solid. I did try a punch on the lip by the bolts but it started to roll over so stopped. Also tried to drive a flat blade chissel into the join on the end above the prop but that didn't work. So stopped before I broke anything else.

It's separated absolutely zero mm. Still looks like it's still bolted on but I cand find any more bolts. 4 on the outside all snapped just below the surface. The trim tab one came out fine same as the one just behind it. Can't see any under the trim tab. Shift rod also has the pin removed.

Sound like the driveshaft and crankshaft splines are jammed with RUST.----Or the stubs of the broken bolts are jammed with aluminum oxide ( white powder )-----This may be a time consuming effort.------Have a freebie 74 model now with the same issue.-----Has only separated 1/8" so far.

Quote:

These bolts often break off due to a process called " hydrogen embrittlement " that occurs on stainless in a salt environment or even fresh water.

So true.....

mlevett said:

Thanks yes shift rod is disconnected, I did the pump on a 1978 model so was aware of how it comes apart just this one seems to be stuck solid. I did try a punch on the lip by the bolts but it started to roll over so stopped. Also tried to drive a flat blade chissel into the join on the end above the prop but that didn't work. So stopped before I broke anything else.

It's separated absolutely zero mm. Still looks like it's still bolted on but I cand find any more bolts. 4 on the outside all snapped just below the surface. The trim tab one came out fine same as the one just behind it. Can't see any under the trim tab. Shift rod also has the pin removed.

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I'm not a hundred percent sure but many evenrudes have 6 bolts holding the lower unit on and one of them is under the trim tab that's difficult to see because it's recessed deeply. Use a flashlight and look up in there.