New Boat Purchase - Stuck Manifold drain plug

[turand]

Hey there, I tried searching for this and couldn't find any particular answer. I plan on buying a 1985 Rinker with a Mercruiser 3.0 140 in really good condition. After looking at the boat, the owner remarked the coolant drain plug on the manifold was stuck and he just left it there. He said he's just been using the drain on the engine block to winterize and hasn't had any issues.

Any advice? The rest of the boat looks in great condition. Would you attempt to remove/replace the stuck manifold plug? I expect it will be quite an effort with a lot of PB blaster or penetrating oil and perhaps an easy out. Or is it just fine to use the engine block plug to drain and flush/load with antifreeze for winterizing?

 

[Bondo]

Would you attempt to remove/replace the stuck manifold plug? I expect it will be quite an effort with a lot of PB blaster or penetrating oil and perhaps an easy out.

Ayuh,..... Welcome Aboard,..... The manifold doesn't drain through the block,....
So,... Yes, fix it by whatever means necessary,....

 

[turand]

Ok, thanks! Should I be scrutinizing the manifold a bit more closely for any potential cracks? Would it be visually obvious?

 

[Rick Stephens]

Where is the boat located? Where temperatures in the winter get below freezing? If so, then the manifold condition is seriously in doubt.

 

[turand]

Where is the boat located? Where temperatures in the winter get below freezing? If so, then the manifold condition is seriously in doubt.

Minnesota, so a big YES on freezing temps, but appears to have stored indoors mostly.

My general idea was to hand feel around the manifold for any indications of a crack and have it run for a while and make sure I see no leakage. Of course, its going to be a gamble since I cannot inspect the interior of the manifold, but I supposed buying a 30+ year old boat will always carry some risk.

 

[turand]

Here is the info on the boat, I wasn't able to get a decent picture of the manifold when I gave it a first visit.

https://www.facebook.com/marketplace/item/4025085607542717

 

[Scott06]

It may actually be ok. I could never figure this out but i winterized my 1990 3.0 for 20 years. I always took that plug out but never git any water to come out ( no it wasn’t plugged ). didn’t make sense to me but the water must have been siphoning out the block via the hose feeding it. always got plenty of water out of the block and never had a frozen block or manifold in upstate NY winters

 

[Rick Stephens]

A crack to worry about in the manifold will be internal, not external. If it leaks, it will put water on your exhaust valves. Safest thing is to pull it and fill the water jacket with acetone and see if it leaks into the exhaust passage.

 

[QBhoy]

Hi. Depending on the manifold that’s on it now...there is a chance it’s been replaced at somepoint with an aftermarket one. Some of them have a fitting you can remove at the very rear and the front of them. Like a 22mm sized head. Just in case it helps.

 

[crazy charlie]

Assuming it is brass and easy to get to,just drill it out starting with small bit and working your way up in size until there is only a small amount left and at that point you can probably tap it out without damaging the manifold.Personally,any time I purchase a boat I immediately replace manifolds,circulator waterpump etc.I start out with new parts because you dont know the age or real condition of the old parts which are parts that can cause catastrophe..Charlie

 

[turand]

Assuming it is brass and easy to get to,just drill it out starting with small bit and working your way up in size until there is only a small amount left and at that point you can probably tap it out without damaging the manifold.Personally,any time I purchase a boat I immediately replace manifolds,circulator waterpump etc.I start out with new parts because you dont know the age or real condition of the old parts which are parts that can cause catastrophe..Charlie

Thanks! I was thinking of doing something similar, I know I was going to do the fuel filter and probably impeller. I hadn't thought about the water pump. I am reasonably handy, but not a gear-head by any stretch of the imagination. I've been watching lots of videos this week on maintenance of the 3.0 and the engine seems pretty easy to work with. How hard is swapping out the manifold? Seems the hardest part is getting it back on because of the weight and aligning the bolts.

 

[Lou C]

What you can do with replacing the manifold is this:
When you get the new manifold it should come with new bolts. Take one of them to the hardware store and buy 2 longer bolts of the same thread/pitch. Then cut the heads off and cut a slot in the stub for a screwdriver. Clean out the threads in the block with a thread chaser. Now thread in these 2 headless bolts into the first and last bolt holes in the head. Slide on the gasket. Then slide on your manifold. Install the rest of the bolts and then remove the 2 headless studs with a screwdriver. Now simply install the last 2 bolts. Much easier this way with a heavy cast iron manifold.

 

[turand]

Great tip, thanks!