Exhaust riser plug hole threads

[i386]

'84 898, Thunderbolt Ignition.

This is the pipe plug hole on the starboard exhaust riser. As you can see, the threads are gone (rusted).

What's the recommended method to make this servicable? Tap bigger? Helicoil?


If I take this part off, I think I should go ahead and address the rust problem. I've never painted hot exhaust parts before. Wire wheel -> Naval Jelly/Ospho and high-heat paint from the parts house ok?

 

[bomar76]

Re: Exhaust riser plug hole threads

Uhh......you don't need a repair, you need 2 new manifolds and risers....those are toast.

 

[MikDee]

Re: Exhaust riser plug hole threads

First get that rust out of there! Use PB Blaster, or something stronger (if you can find it! Thank the EPA for watering down anything GOOD!) Then invest in a pipe plug tap 1/4" NPT or 3/8" NPT not sure? (common at any hardware store) it SHOULD be that size, and carefully tap it out using the proper tapping oil, or (any oil) You really wanna just follow whats left of the old threads, a new brass pipe plug, is tapered smaller at the bottom, larger at the top, it should seal it, once you screw it in far enough.

By the way, if you want, get a brass pipe plug, and try the pipe plug on another cleaner drain hole, to see what I mean.

I wouldn't let that stop me from running the motor, even if I had to plug it with a round wooden dowel! (disposable! that would swell, & seal, if water hits it)

 

[woosterken]

Re: Exhaust riser plug hole threads

how about an expandnable rubber plug like the bildge plug?

woosterken

 

[tommays]

Re: Exhaust riser plug hole threads

I cant tell if the hole is rusted away OR just nasty from leaving the plugs out

The real issue is at the joint between thw manifold and ellbow as it is only a 1/4" wide when new

 

[i386]

Re: Exhaust riser plug hole threads

First get that rust out of there! Use PB Blaster, or something stronger (if you can find it! Thank the EPA for watering down anything GOOD!) Then invest in a pipe plug tap 1/4" NPT or 3/8" NPT not sure? (common at any hardware store) it SHOULD be that size, and carefully tap it out using the proper tapping oil, or (any oil) You really wanna just follow whats left of the old threads, a new brass pipe plug, is tapered smaller at the bottom, larger at the top, it should seal it, once you screw it in far enough.

By the way, if you want, get a brass pipe plug, and try the pipe plug on another cleaner drain hole, to see what I mean.

I wouldn't let that stop me from running the motor, even if I had to plug it with a round wooden dowel! (disposable! that would swell, & seal, if water hits it)

About the pipe plug. If you'll remember from my other thread I think the pipe plug I found goes there. There is a pipe plug in the port side riser.

I believe it's the one on the lower left of this picture. Notice the threads are gone on it too. I did not remove this from the riser myself. Like I said before, all these plugs were in the drivers console cup holder. I don't think there's going to be anything left to tap out without drilling larger. Are these manifolds cast iron? I was thinking cast iron can't be drilled and tapped.

I can maybe see replacing these parts (if I can't restore them myself), but I don't think buying a new set of manifolds and risers is a good idea when I don't know if it even runs.

 

[tommays]

Re: Exhaust riser plug hole threads

A CHEEP NPT tap in the correct size will clean out the hole and tell you if it is dirty from leaving out the plugs or BAD


In any case it should be good enough to fire the motor as i am thinking the boat was allways in a fresh water area

 

[MikDee]

Re: Exhaust riser plug hole threads

Bring one of those with you, then go to home depot, loews, or Ace hardware, and get NEW brass pipe plugs that size (Thats all they are) I know yours have fancy thumb handles on them

Yes, a cheap National Pipe Thread Tap will do

 

[Don S]

Re: Exhaust riser plug hole threads

There is only 2 pipe plugs in the picture. The winged plugs are not NPT, they are straight thread and fit into these fittings.

 

[i386]

Re: Exhaust riser plug hole threads

Bring one of those with you, then go to home depot, loews, or Ace hardware, and get NEW brass pipe plugs that size (Thats all they are) I know yours have fancy thumb handles on them

Yes, a cheap National Pipe Thread Tap will do

Again, the plugs in the block and the exhaust manifolds are the t-handle drain **** type. The threads in these are fine AFAIK. They screw into a bushing. With repeated use the bushing threads may go bad. If so, all you need is a new bushing and you're back in business. Not the case with the risers though...

The plugs in both port and starboard risers ALREADY ARE brass pipe plugs. The port side pipe plug is still in the riser. The starboard side is the one that was removed when the engine was "winterized". Not only are the plug threads gone (yup brass is soft, easy to get a new plug), the threads in the riser are gone. I don't think there's anything left to tap out w/o going to a larger size.

Just trying to get a game plan together. I appreciate the help and don't mean to come off as argumentative (I'm the one that doesn't know what I'm doing.), I just don't think we're on the same page as far as understanding all the conditions of the problem.

 

[tommays]

Re: Exhaust riser plug hole threads

As i repiar high pressure steam leaks in pipes i fully understand rusted pipe fittings however i can only look at the picture and guess as we have to clean out NPT holes all the time and it looks like there is enough to test the motor

If you feel its shot the next size will be to big and a regular bolt tap may clean it up enough to do a temp plug with a bolt

Cast iron taps very easy

 

[Bondo]

Re: Exhaust riser plug hole threads

Ayuh,......

If the Riser is That Rusted,....... It's JUNK.......

I wouldn't even Try to renew the threads..... If they're that Bad,.....
The Rest of the riser is probably AS Bad,.....
And when it $h!ts,...... It'll take the Motor With It................

 

[i386]

Re: Exhaust riser plug hole threads

Ayuh,......

If the Riser is That Rusted,....... It's JUNK.......

I wouldn't even Try to renew the threads..... If they're that Bad,.....
The Rest of the riser is probably AS Bad,.....
And when it $h!ts,...... It'll take the Motor With It................

Well, you may be right but we'll see...

I got the riser off. Took about 45 mins. Didn't break anything. There were some 50 cent piece sized flakes of rust on the inside. I got those with the shop vac from the exhaust manifold and the exhaust elbow. I don't know what would happen if all that were to go through the rest of the exhaust system, but probably not good.

Anyway, the threads. Upon closer examination, the hole is fairly smooth, but "brassy". Remember that brass plug is about threadless. If I'm lucky, those brass threads may have stripped out and remained in that hole giving the appearance of a stripped hole.

Another point to consider is there's an identical hole and plug on the opposite side of the riser. It's not exactly convienent to get to, but if I had to I could get the bad side permanently plugged and use the other one.

Now the interesting part. We have a Wheelabrator (industrial abrasive blasting equipment for all parts great and small) plant here and I happen to have a buddy that works there. I'm going to hand this part off to him and see how it cleans up. I've got nothing to lose and buying new manifolds and risers for an engine of unknown condition isn't smart IMO.

I'll let y'all know what happens.

 

[Don S]

Re: Exhaust riser plug hole threads

I KNOW what a Wheelabrator is (at least I know about one of them), it's a steel shot peaning machine. It also can destroy cast iron skillet (don't ask). If that is the same thing, it will wreck the machined area and possibly the complete manifold. If your manifolds are that plugged up with stuff, replace them. It's the inside of the manifolds flaking off. When it rust thru, you get water in the engine, and can then say good buy engine, not just good buy old manifolds and risers.

 

[i386]

Re: Exhaust riser plug hole threads

I KNOW what a Wheelabrator is (at least I know about one of them), it's a steel shot peaning machine. It also can destroy cast iron skillet (don't ask). If that is the same thing, it will wreck the machined area and possibly the complete manifold. If your manifolds are that plugged up with stuff, replace them. It's the inside of the manifolds flaking off. When it rust thru, you get water in the engine, and can then say good buy engine, not just good buy old manifolds and risers.

I hear ya, but let's see what the guys in the shop say. They have dozens of machines there with many types of media and processes. It's one of the plants where they manufacture the machines, but they have a bunch of machines there to do jobs with too. They can do anything from Abrams tanks to small delicate parts. I was told they can also clean hollow parts such as manifolds. They have ways to protect machined surfaces from damage.

If it was a known good engine, replacing the parts would be a no brainer. I appreciate your help and respect your experience.

I didn't even know what an exhaust riser, exhaust elbow, gimble, cutout switch, trim sender and a lot of other stuff was this time last week.

I'll let you know what they say.

 

[MikDee]

Re: Exhaust riser plug hole threads

If it was a known good engine, replacing the parts would be a no brainer. I appreciate your help and respect your experience.

I didn't even know what an exhaust riser, exhaust elbow, gimble, cutout switch, trim sender and a lot of other stuff was this time last week.

I'll let you know what they say.

Hey i386, I'm sorry if I steered you wrong on the drain plugs :redface:
Yes, it comes back to me now the winged plugs are a different thread.

I know what you mean about buying new manifolds if the engine is bad, But it is risky trying those old ones (even if you get them all cleaned up), I'd worry about them being too thin, and cracking, or blowing out, on the initial start up

I know you're in a pickle now, But, think about this, if you really want to get this boat going we both know that eventually you're gonna have to buy new manifolds, or you won't be able to trust using the boat with the old ones, besides if you decide to repower, you'll have the new manifolds ready. Also, I bet there's someone on this board that will buy the manifolds off you, if you decide to give it up.

Personally I'd forget about the trim sender, it's not that important (I never had a working one on any of my boats anyway) Plus, I believe you have to take the bell housing off to replace it, no fun!

Good Luck, we're all rooting for ya, Mike

 

[JustJason]

Re: Exhaust riser plug hole threads

can you post pictures of the actual inside of the risers that you took off?

 

[wca_tim]

Re: Exhaust riser plug hole threads

If you're going to use those to test run it, i would make sure I pressure tested before running, and then once you decide you've got it going, replace as soon as you can...

wouldn't is suck to bend a rod, valves, destroy a cylinder or 3, the list goes on, etc... trying to get it going?

manifolds and risers are cheap compared to internal engine components... and compared to your time and effort...

 

[i386]

Re: Exhaust riser plug hole threads

can you post pictures of the actual inside of the risers that you took off?

Sure can...

 

[JustJason]

Re: Exhaust riser plug hole threads

hmmm not the worst looking ones i've ever seen. If your going to try to save a few bucks and clean those up make sure you run a file over the mating surfaces to make sure they are true.