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88 PS190
03-15-2013, 12:10 AM
Are all exhaust manifold drain plugs 3/4" NPT?

I'm tearing into the recent acquisition, it has some sort of galvinized manifold plugs, that seem to be corroding.

Want to go bronze or plastic, but forgot to grab the plug out of the boat for comparison tomorrow @ the hardware - any takers?

Table Rocker
03-15-2013, 12:29 AM
3/4 NPT is correct.

88 PS190
03-15-2013, 12:58 AM
Very good.

If nothing else this may form some sort of reference database for these things.

I very much wish we had that, I use a Motorcycle forum some that does, essentially cross references for part numbers, thread sizes etc.

mikeg205
03-15-2013, 10:47 AM
pictures?

Table Rocker
03-15-2013, 12:04 PM
I picked up some plugs like this one. You can use a 1/2" drive ratchet to install or remove them. Overkill, but...

88 PS190
03-15-2013, 06:45 PM
I picked up some plugs like this one. You can use a 1/2" drive ratchet to install or remove them. Overkill, but...


That's what my boat already has, I don't think cast iron or any sort of steel plug is right when you're talking the steel manifolds and an open loop cooling system.

Just due to risks of corrosion, I'd rather go with something that will be easier to remove, also - those steel plugs just don't seem to "thread in" all that far.

When I pulled one I was sure I had snapped it off, because after 1.5 turns the manifold gushed water everywhere. With my 88 the plug seems to thread in a good 3-4 turns, and those are bronze. I think the softer metal gets around the imperfections in the taper/thread.

Table Rocker
03-15-2013, 07:45 PM
That's what my boat already has, I don't think cast iron or any sort of steel plug is right when you're talking the steel manifolds and an open loop cooling system.

Just due to risks of corrosion, I'd rather go with something that will be easier to remove, also - those steel plugs just don't seem to "thread in" all that far.

When I pulled one I was sure I had snapped it off, because after 1.5 turns the manifold gushed water everywhere. With my 88 the plug seems to thread in a good 3-4 turns, and those are bronze. I think the softer metal gets around the imperfections in the taper/thread.Those are chrome plated brass.

http://www.amazon.com/gp/product/B0046A88OK/ref=oh_details_o01_s01_i04?ie=UTF8&psc=1

I wrap them with teflon tape and run them in.

FrankSchwab
03-15-2013, 07:50 PM
On mine, the plugs are plastic and have drains screwed into them. I'm intimately familiar with this because one of the plastic plugs broke off when I was winterizing.

XtwentyNot
03-16-2013, 12:24 AM
That's what my boat already has, I don't think cast iron or any sort of steel plug is right when you're talking the steel manifolds and an open loop cooling system.

Just due to risks of corrosion, I'd rather go with something that will be easier to remove, also - those steel plugs just don't seem to "thread in" all that far.

When I pulled one I was sure I had snapped it off, because after 1.5 turns the manifold gushed water everywhere. With my 88 the plug seems to thread in a good 3-4 turns, and those are bronze. I think the softer metal gets around the imperfections in the taper/thread.

My old boat had the same issue. I bought a tap, brass bushing, and brass plug. I tapped the manifold, installed the brass bushing, and removed the plug to drain. Here's some google pics for reference. My auto parts store had the tap and brass parts.
91198
http://img.tapatalk.com/d/13/03/16/vevuseva.jpg

New owner still hasn't had to buy manifolds...

88 PS190
03-16-2013, 02:34 PM
Not saying I need manifolds, the threads look nice and clean. I just don't think the steel plugs it has thread in far enough, the taper seems too short,

Trip to hardware was rescheduled to today.

XtwentyNot
03-16-2013, 04:01 PM
Sorry, I read what you were saying again after posting. Please disregard my post. I guess I've spoken prematurely. I didn't realize it was a deep enough problem. I haven't experienced that one. I wish you the most success in working it out. Maybe it's too fat? Sometimes the problem is embarrassing,