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How many drain plugs on Mercruiser 502 MAG MPI?

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How many drain plugs on Mercruiser 502 MAG MPI?

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Old 12-04-2011 | 01:28 AM
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Default How many drain plugs on Mercruiser 502 MAG MPI?

Doing the winterizing myself, I found 5 of them but I thought there were 6 plugs (3 per side)? Or am I just crazy?
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Old 12-04-2011 | 06:13 AM
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Should only be two places that actually drain the water from the block, one on each side in the middle. One likely has a flared hose fitting for water pressure and the other a petcock or actual plug you can remove.
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Old 12-04-2011 | 06:42 AM
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Originally Posted by Griswald
Should only be two places that actually drain the water from the block, one on each side in the middle. One likely has a flared hose fitting for water pressure and the other a petcock or actual plug you can remove.
That would be "block drains" only. He's also got to drain the exhaust manifolds, circulating pump and raw water punp. The older 502s did not have drain plugs on the raw water pumps. You needed to pull the hoses.

And a special note to the OP, make sure you run a zip tie / coat hanger / piece of wire into the openings after you pull the plugs - particularly the block drains. Sediment will occasionally plug the openings even after you pull the plugs.
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Old 12-04-2011 | 05:30 PM
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Default Drain plugs

There should be one on each side of the block, one on each exhaust manifold and one for the cool fuel.. That would make a total of 5! Your not crazy!!
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Old 12-04-2011 | 10:46 PM
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What year do you have? What is your engine serial number?
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Old 12-05-2011 | 05:15 AM
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Originally Posted by winkman
There should be one on each side of the block, one on each exhaust manifold and one for the cool fuel.. That would make a total of 5! Your not crazy!!
Yup....... the 1 cool fuel drain on the port side of the engine
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Old 12-05-2011 | 07:52 AM
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Originally Posted by Too Stroked
That would be "block drains" only. He's also got to drain the exhaust manifolds, circulating pump and raw water punp. The older 502s did not have drain plugs on the raw water pumps. You needed to pull the hoses.

.
Originally Posted by griswald
Should only be two places that actually drain the water from the block
The way it was written eluded to the block, which is what I commented on

Last edited by Griswald; 12-05-2011 at 08:01 AM.
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Old 12-06-2011 | 09:51 PM
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Thanks for the tips guys, helps me out quite a bit!

LakeDude - I have a 99 Baja 272, original engine.
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Old 12-07-2011 | 03:50 AM
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Originally Posted by PDubs
Thanks for the tips guys, helps me out quite a bit!

LakeDude - I have a 99 Baja 272, original engine.
Like said above you have 5.

The year you have is the cool fuel system, Had you had an older non cool fuel system you still would have had 5, but the 5'th one would have been in the power steering cooler with a brass plug.
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