Carver Owners Forum

Hi,
We are first year with the Carver mariner and seeking some advice on where the drain plugs go on the Crusader 5.7 mpi engine. There are six in total and i am attaching a picture of 3. Particularly interesting is the one with a hole in it. Just want to make sure not to use it at incorrect drain plug location and block any water flows.

Much appreciated.

Welcome aboard. Difficult to say as they can go in either the manifolds or block. There should be two for each block and at least one for each manifold so at minimum there should be four per engine unless a modification has been made. The plug with the hole in it goes into a mating fitting specifically designed to accept that plug. The block drains are low in the block just above the oil pan about half way between front and back. There will be one on each side of the block. Manifold drains are dependent on the type of manifold you have but they're typically at the bottom rear of the manifold. If you have a hard time finding the holes, it won't do any harm to fire up an engine for a few seconds, shut down, then take a quick look at where the water is coming from.

Were these left off from winterizing? If so, it's not a good idea. After winterizing is complete, drain plugs should be reinstalled. Plugs are left out by people that don't use antifreeze to winterize so they leave plugs out to avoid water pooling in the bottom of the block that may have not drained initially so it doesn't freeze. The problem with leaving plugs out is that the threads in the block quickly corrode which makes it difficult to reinstall the plugs in the spring. Eventually, the corrosion is bad enough that it wrecks the threads on the soft brass plugs so you replace with new plugs and chase the threads all the time. Eventually the corrosion gets bad enough over the years and completely deteriorate all the threads making it impossible to reinstall the plugs. If you're going to leave the plugs out, you need to coat the threads with a product that will prevent the threads from corroding.

Welcome to the forum......do a search for your year crusader 5.7mpi service manual or crusader parts, in that you should find all the drain locations and pertinent plugs for the locations.The manuals will come in handy later, trust me. What year are your engines?..the 2 on the left look like you expect to see as used drain plugs....the shiny one looks unused and specific....... Good luck man......

You mean six for each engine or you just have six total? Is your engine raw water cooled or fresh water cooled? If fresh, is it a half or full system? That would determine how many plugs would need to be pulled to winterize.

Mine have six on each engine that I remove. Mine is raw water cooled. Two on the block, as Viper has noted, two on the manifolds, as the lowest spot, then two on the risers. The two on the risers are the most difficult because they go up from the bottom of the riser.

I also have ones on the raw water pump, but I don't typically take those out.

None that I have look like the one shiny one you show. If that is one of the six for each engine I wonder if they substituted it for a real plug. If you have six total and the engines are fresh water cooled, then I wonder if that other plugs are for something else, like the genset or water heater?

OK, someone tell me I'm wrong...
Isn't that engine a full fresh water cooled engine? And if so, why is the block being drained for winterization?

The plug with the hole is very common on Merc engines and manifolds of later vintages. You don't have to actually remove them, that's the reason for the design with the holes. There is a hole in the middle of the hex head of the plug, when you loosen the plug enough, water drains out of the head of the plug without removing the plug completely. You can remove these and leave them out all winter because the mating fitting always stays in the block or manifold, and since the two piece assembly is brass, you don't have to worry about the threads corroding, not the case with the other plugs though.

It's my experience that the plug with the hole in it goes on the bottom of the exhaust manifold (generally on the bottom of the exh. manifold, toward the rear of the motor. Should have a protruding boss where the plug goes.), while the other two go in the exhaust manifold riser. If they were used as block drains, it should be fairly obvious where they go, but it's not uncommon for the block drains to remain plugged.