rookie mistake

[picker523]

Well I started re-installing the outdrive on the new transom of my 87 glastron and I discovered the bolts on the center of the bellhousing are mercriuser bolts. I had gone to the local nut and bolt place to replace the old rusty bolts that came out of my alpha 1 and the guy gave me something that appeared to be the same. Like a idiot I attempted to bolt the bellhousing to the transom without checking it first and messed up the first 1/4" of threads. Has anyone had to deal with this and how did you fix it?

 

[RCSConstruction]

Re: rookie mistake

Can you clean up the threads with a tap/die? It should at least clean up the 1/4" of bad threads so you can get to the good threads.
How many good threads are left before it is tightened?

 

[Coors]

Re: rookie mistake

If you can tap from the opposite direction, do that to clean the threads.

 

[freelunch]

Re: rookie mistake

If cleaning them up doesnt work just go buy some new studs and replace them

 

[Limited-Time]

Re: rookie mistake

You can always go the Heli-Coil route. But there may be issues using the SS thread inserts in an alum. housing in a Marine application. Maybe Bond-o, Don, or one of the other more experanced(sp) guys can chime in on that option.

 

[picker523]

Re: rookie mistake

Can you clean up the threads with a tap/die? It should at least clean up the 1/4" of bad threads so you can get to the good threads.
How many good threads are left before it is tightened?

There are quite a bit of threads left but the problem is trying to get past the messed up threads. The threads are merc threads so I'm sure a standard tap wouldn't work. I'm hoping that by using some new merc bolts I can get it to retap the holes and the remaining merc threads line up once I get past the bad ones but it doesn't seem very likely. THe threads are the center threads on the bolt pattern and from the back side it looks like a sealed tube about 2'" long that houses the threads. I appreciate all the input ... keep it coming!

 

[Limited-Time]

Re: rookie mistake

Some one jump in here if I'm wrong but I hardly think Merc designed there own thread form. They may have gone with a non standard pitch, or size. Like a NEF (national extra fine) as opposed to a NC (national course)or NF (national fine). If you can detirman the diameter and pitch (how many threads per inch) you can get the correct tap and re-chase the threads. That or drill out just the damaged portion of the threads and the correct bolts should start in.

 

[Fishermark]

Re: rookie mistake

Just to be clear what you're talking about...
Are you referring to the six bolts / studs sticking out of the bell housing that you attach the outdrive to? And the rusty part you are replacing is a NUT, not a BOLT, right? Those studs are not Mercruiser specific, they are fine thread bolts using fine thread nuts. 7/16" if memory serves me correctly - maybe 1/2" - either way, a good hardware store or marina should be able to help you out. You want to use stainless steel nylon lock nuts, fine threaded.

 

[Fishermark]

Re: rookie mistake

If you have enough thread left, you can use a file to grind away the bad threads and then use a die to clean up the rest.

 

[Gary H NC]

Re: rookie mistake

Some one jump in here if I'm wrong but I hardly think Merc designed there own thread form. They may have gone with a non standard pitch, or size. Like a NEF (national extra fine) as opposed to a NC (national course)or NF (national fine). If you can detirman the diameter and pitch (how many threads per inch) you can get the correct tap and re-chase the threads. That or drill out just the damaged portion of the threads and the correct bolts should start in.

I agree!!! Not special Merc threads!! Find the correct die and fix what you have.

 

[Coors]

Re: rookie mistake

I have no clue; did merc go metric?

 

[Coors]

Re: rookie mistake

sae, or nf. okay, fine or course thread.

 

[Don S]

Re: rookie mistake

It's a very standard 7/16-20 NF thread. The nuts, however, are chrome plated bronce nylocs. That is so after being in the water they won't rust onto the SS studs like a grade 8 nut. You also don't want to use a SS nylock as it can gall the threads on the stud.
Best bet is to replace the studs. The chances of running a tap on them and getting the threads to line up with the undamaged ones are slim if there is a lot of damage in the first 1/4"
You can't just remove them and go from the other end because it's a course thread on the other end.
Next time, use the right parts........ it's cheaper in the long run.

 

[picker523]

Re: rookie mistake

It's a very standard 7/16-20 NF thread. The nuts, however, are chrome plated bronce nylocs. That is so after being in the water they won't rust onto the SS studs like a grade 8 nut. You also don't want to use a SS nylock as it can gall the threads on the stud.
Best bet is to replace the studs. The chances of running a tap on them and getting the threads to line up with the undamaged ones are slim if there is a lot of damage in the first 1/4"
You can't just remove them and go from the other end because it's a course thread on the other end.
Next time, use the right parts........ it's cheaper in the long run.

I think there's a mis-understanding as to which bolts I'm talking about . It's the bolts that hold the entire outdrive to the transom not the foot to the bellhousing. There Are 6 bolts that go through the transom . 2 studs in the outdrive assembly , the 2 anode bolts, and the 2 that go through the transom and screw into the outdrive housing. The last 2 are the ones I'm talking about. I would like to re- tap the messed up part without altering the good ones but I doubt that's possible.

 

[Bt Doctur]

Re: rookie mistake

remove the housing and retap

 

[Bondo]

Re: rookie mistake

There Are 6 bolts that go through the transom . 2 studs in the outdrive assembly , the 2 anode bolts, and the 2 that go through the transom and screw into the outdrive housing. The last 2 are the ones I'm talking about. I would like to re- tap the messed up part without altering the good ones but I doubt that's possible.

Ayuh,........... You're Right,.......
No Way in 'ell you're going to retap them without Pulling the outer housing........
You're talking about the 2 Center Bolts,...... Not the Studs, or the Aluminum bolts......

And You're Wrong about them being some Special Thread,.........
I Believe they're Standard 7/16" Course,...... They Might be the 7/16"- 20 Fine,......
Don would Know,..... I'll have to Go Look......... But I Know they're Not Special.........

If you've Really Buggered it up Real Bad,....... A Heli-coil would put you back on the Water,......
No Problem there......
You could even go to the standard Course thread at that time,.. IF by chance that they Are a Fine thread......

It's Not the End of the World,......... But the Housing Does have to come back Off...........

 

[picker523]

Re: rookie mistake

Ayuh,........... You're Right,.......
No Way in 'ell you're going to retap them without Pulling the outer housing........
You're talking about the 2 Center Bolts,...... Not the Studs, or the Aluminum bolts......

And You're Wrong about them being some Special Thread,.........
I Believe they're Standard 7/16" Course,...... They Might be the 7/16"- 20 Fine,......
Don would Know,..... I'll have to Go Look......... But I Know they're Not Special.........

If you've Really Buggered it up Real Bad,....... A Heli-coil would put you back on the Water,......
No Problem there......
You could even go to the standard Course thread at that time,.. IF by chance that they Are a Fine thread......

It's Not the End of the World,......... But the Housing Does have to come back Off...........

It's already off so that's not a problem. I'm trying to put it back together after fixing the transom. I've never used a Heli-coil but I'm willling to give it a shot. Should it be strong enough?

 

[Bondo]

Re: rookie mistake

Should it be strong enough?

It's a Non- Issue.......

Be Careful,... Go Slow,..... And keep it Square,+ True............

 

[polypenguin]

Re: rookie mistake

If you have 2" of thread total, and only lost 1/4" of thread, my fix would be to drill out the 1/4" of bad thread and just depend on the rest to hold it together. I don't always do things the "right" way.

 

[picker523]

Re: rookie mistake

If you have 2" of thread total, and only lost 1/4" of thread, my fix would be to drill out the 1/4" of bad thread and just depend on the rest to hold it together. I don't always do things the "right" way.

I would but I don't think I can do it without messing up the good threads.