lower unit bolt broke off

[friderday]

I have a 30hp Mariner. Needs water pump. Previous owner, apparently, tried to drop lower unit. One of the 4 bolts snapped off flush. Any thoughts on how to proceed getting lower unit off? The other 3 bolts are still on. They, I'm sure will require some heat/freeze to coerce them, & good likelihood they, too may snap off. It's never fun when a bolt head breaks off, but because of the placement of the cavitation plate, how does one drill out what's left of the bolt? There's only about 3 inches between bolt head & cav plate. Any ideas?

 

[James R]

Re: lower unit bolt broke off

Are they bolts or are they nuts on studs. You did not tell us model and year so that we can look at the drawings. Has this motor been used in salt water.
Dont panic yet.

 

[Bob_VT]

Re: lower unit bolt broke off

Pull all the other bolts and remove the lower unit. The threads are in the upper half and it should come off and even leave a piece exposed to help remove it.

The bolts are stainless steel and hard to drill but a slow drill and a cobalt bit will do it.

 

[friderday]

Re: lower unit bolt broke off

Thanks BobVT...that is our plan..I was thinking the threads were up top, but yes, it was in saltwater. Pretty well cared for, actually, but we all know saltwater is the enemy. James...I think its around a 1992. Either of you have any feedback on heat vs. freeze products to loosen things up? Other than patience, due diligence, & prayers to the bolt gods...we have know guaranteed plan...

 

[quicktach]

Re: lower unit bolt broke off

KROIL is a good penetrating oil for starters.

 

[friderday]

Re: lower unit bolt broke off

I was able to apply a little heat to the three remaining bolts. They came off with surprising ease. More good news-the water pump/impeller looked brand new. Appears the "failure to pump water" came from some crustaceans & debris. Cleaned things out & all is well as far as pumping water. Now the bad news. The first thing I did when I got the motor was drain lower unit. The oil was in perfect shape, no water, no metal shavings. I put new oil in at that time. Our few test runs at the dock, apparently were enough to prove otherwise. While we had the water pump off, we noticed milky oil leaking from top seal at the drive shaft. I have never had much luck seal pulling & with the age of this motor('92) & corrosion, I doubt a pro will have any luck either. I am taking to a pro this morning to see what he says, but accepting the reality that I might have an expensive paper weight in the garage.

 

[friderday]

Re: lower unit bolt broke off

bad news today...mechanic unable to help with this lower unit. too much corrosion. could probably get them out but no threads to put back in....sooooo any suggestions on finding lower gear case for this? otherwise part out and start over.

 

[orbanp]

Re: lower unit bolt broke off

bad news today...mechanic unable to help with this lower unit. too much corrosion. could probably get them out but no threads to put back in....sooooo any suggestions on finding lower gear case for this? otherwise part out and start over.

Any chance of putting Helicoil in it?

Peter

 

[sam am I]

Re: lower unit bolt broke off

Helicoil perhaps........Is there enough metal wall left over drill it and tap for appropriate size?

 

[sam am I]

Re: lower unit bolt broke off

Any chance of putting Helicoil in it?

Peter

Sry Pete, posted at same time but.......great minds think alike eh?

 

[wired247]

Re: lower unit bolt broke off

If you can get the drive shaft out you can take it to a machine shop and they can lock it down on the bed of a horizontal mill . A 2 flute carbide cutter will make short work of that broken stud.

 

[friderday]

Re: lower unit bolt broke off

sorry, I could see how this got confused. See post #6...the bolts came off easily with a little heat applied. I am referring to the seals leaking & lower unit oil milky. there are no threads left on inner housing...even if we get the lower seals out, no threads to get that nut??? that holds them in back on. Lower unit just kinda corroded. Need a new "used" one in better shape or this will be a $400 paper weight.

 

[Mi duckdown]

Re: lower unit bolt broke off

Pics.

 

[carholme]

Re: lower unit bolt broke off

I am sure that if you remove the nut you may be surprized to see the threads under the nut are still quite useable. If for some reason they are not, it hasn't cost you anything. Get the nut out first.

Gerry

 

[friderday]

Re: lower unit bolt broke off

the nut is removed...in 4 or 5 corroded pieces. took it over to a merc shop around the corner(didn't even know it was there). This guy gave me a couple options of hope: 1)I can expand my search for another lower unit to not only Mariner, but Merc 30hp, & Yamaha 30hp as this engine was built in Japan(says so on the plate), or 2)he is sure the threads are not re-usable & that the carrier is corroded in anyway & probably doesn't need the nut anyway. Therefore, he might try to replace the upper seals(that area under water pump not at all corroded), & hope everything stays put down below. I got my feelers out for another lower unit for now.

 

[mccoytr]

Re: lower unit bolt broke off

If you are still looking a lower unit might want to give these folks a try. Big sale as they are trying to pave lot.

Georgia Boat Broker, Used Boat Dealer - Cruisers, Fishing Boats, Sailboats, Yachts, Inboard Outboard Motors in GA

 

[mccoytr]

Re: lower unit bolt broke off

One other idea for you. Instead if a helicoil there may be enough side wall to retap with a standard thread and use JBweld to hold a stud in place, since it was built in Japan it is more then likely metric. You would not need to tap a complete thread just enough for the threads to work and JBweld would fill up the gaps making all secure. Just a thought.

 

[Faztbullet]

Re: lower unit bolt broke off

I your going to look to replace the mid 70's to late 80's Yamaha 20/25 Mariner 25/28 units will work also as they are thru hub exhaust and you can use a above prop exhaust if you cant find a thru prop one.

 

[Texasmark]

Re: lower unit bolt broke off

KROIL is a good penetrating oil for starters.

Kroil was the penetrating oil of choice when I was in industry. Couldn't find a dealer so did a www, got their home address and bought it directly for my personal use.

Mark