Mercruiser 188 Open Cooling System

[IslandExplorer]

Hello, was wondering if anyone happens to know where I can find a flow chart diagram showing the cooling system on a Mercruiser 188 (Ford 302) with the old log style manifolds. I have found diagrams of similar setups but usually a GM 5.0 or an engine with osco manifolds and such- not one that looks like mine yet. Any help with this would be appreciated!

 

[Scott Danforth]

look in the factory service manual for your 188

 

[IslandExplorer]

Here are some pictures in case that helps:

 

[IslandExplorer]

look in the factory service manual for your 188

I would but I do not own one unfortunately. Is it downloadable or available free online anywhere?

 

[IslandExplorer]

This is about all I can tell from tracing the hoses. Not sure how the flow goes as in direction, to where first, etc.

 

[Scott06]

I would but I do not own one unfortunately. Is it downloadable or available free online anywhere?

Most of the free sites get shutdown for (understandable) copyright infringement. Best bet is to determine what manual number covers your engine and look on ebay for a used copy.

this is for the 351 version but I think has the diagram you are looking for . you have to expand the window to see the thread scroll down for the pic

https://www.justanswer.com/boat/5xrqd-looking-fwc-thermostat-housing-351-ealier.html

 

[Scott Danforth]

I would but I do not own one unfortunately. Is it downloadable or available free online anywhere?

no, available used on ebay, or new from https://publications.brunswick.com/

any downloadable or PDF copy would be in copyright violations.

 

[IslandExplorer]

Thank you both! I do intend to get a manual at some point if I can. Just looking to winterize the motor and understand the cooling system better. Hoping I can convert it to at least a half fresh water system before next spring but not sure if I'll be able to swing getting an intercooler setup.

 

[IslandExplorer]

Do you know if it is critical to get the thermostat open (or remove it) before switching to antifreeze inflow? I would think it is but videos I have seen of people doing it are only sometimes doing that. If the engine is known to reliably drain out really well with the plugs removed and be fine that way I might trust that but I would expect there to be pockets of fresh water trapped in the block. This is my first engine-out mercruiser winterization.

 

[Scott06]

Thank you both! I do intend to get a manual at some point if I can. Just looking to winterize the motor and understand the cooling system better. Hoping I can convert it to at least a half fresh water system before next spring but not sure if I'll be able to swing getting an intercooler setup.

there should be block drains on either oil pan rails, drain them there will be some sort of drain plug on bottom of each exhaust manifold drain those, and pull bottom of big J hose on circ pump.

Never have done a log manifold as they were before my time but pull the hoses on thermostat and make sure they are empty blow them out or chase with appropriate antifreeze for your ambient temps.

the issue you may run into is merc hasnt used a ford engine or log manifolds for about 40 years, so not a lot of current info on the web

 

[Scott06]

Do you know if it is critical to get the thermostat open (or remove it) before switching to antifreeze inflow? I would think it is but videos I have seen of people doing it are only sometimes doing that. If the engine is known to reliably drain out really well with the plugs removed and be fine that way I might trust that but I would expect there to be pockets of fresh water trapped in the block. This is my first engine-out mercruiser winterization.

yes thermostat must be open but if it were me just drain the block and associated systems vs running AF. If really want to do AF to do it right you need to drain it first otherwise too much risk of diluting the AF

 

[Scott Danforth]

Do you know if it is critical to get the thermostat open (or remove it) before switching to antifreeze inflow? I would think it is but videos I have seen of people doing it are only sometimes doing that. If the engine is known to reliably drain out really well with the plugs removed and be fine that way I might trust that but I would expect there to be pockets of fresh water trapped in the block. This is my first engine-out mercruiser winterization.

Stop.

Do not watch the block-buster videos

Read this first https://forums.iboats.com/threads/winterizing-inboard-and-i-o.770207/

 

[IslandExplorer]

there should be block drains on either oil pan rails, drain them there will be some sort of drain plug on bottom of each exhaust manifold drain those, and pull bottom of big J hose on circ pump.

Never have done a log manifold as they were before my time but pull the hoses on thermostat and make sure they are empty blow them out or chase with appropriate antifreeze for your ambient temps.

the issue you may run into is merc hasnt used a ford engine or log manifolds for about 40 years, so not a lot of current info on the web

Thanks for the detail! I followed your directions and removed thermostat housing to be totally sure the passage was open and chased all the lines with the RV antifreeze from thermostat pocket. Saturated the whole system to overflow. I also then then circulated it through the block really well with a drill. It eventually started pouring out pink fluid like crazy. I really wanted to see it pumping through somehow so that was nice. And you're right, this particular Mercruiser and manifold setup is a real relic of a bygone era and definitely hard to find a lot of info on it or other people still running them. Pulling those plugs and the J hose seemed to really thoroughly drain it all out nicely though just like you said. Tomorrow I'll blast it out good with some compressed air too while it's still light out.

 

[IslandExplorer]

Stop.

Do not watch the block-buster videos

Read this first https://forums.iboats.com/threads/winterizing-inboard-and-i-o.770207/

Thanks that's an awesome detailed writeup!

 

[Scott06]

Thanks for the detail! I followed your directions and removed thermostat housing to be totally sure the passage was open and chased all the lines with the RV antifreeze from thermostat pocket. Saturated the whole system to overflow. I also then then circulated it through the block really well with a drill. It eventually started pouring out pink fluid like crazy. I really wanted to see it pumping through somehow so that was nice. And you're right, this particular Mercruiser and manifold setup is a real relic of a bygone era and definitely hard to find a lot of info on it or other people still running them. Pulling those plugs and the J hose seemed to really thoroughly drain it all out nicely though just like you said. Tomorrow I'll blast it out good with some compressed air too while it's still light out.

Did you drain the block too don’t know exactly where they are on your ford but will have drain plugs on either side of the block

 

[IslandExplorer]

 

[IslandExplorer]

Did you drain the block too don’t know exactly where they are on your ford but will have drain plugs on either side of the block

Yes, I did and you're right, one on each side. The two threaded plugs (about 1/2 I'm guessing) are just above the oil pan, one front right, other back left. Each Dumps out coolant, about 2 gallons each and noticed they are not connected as one went dry and then pulled the other and it drained a ton too. The J hose dumped a separate gallon plus at least. Crazy how much volume the block holds!

Each log has a center bottom plug I pulled and those seemed to drain out really well. All drains have been poked out really well previously including with small magnet stick while it was all dry and I was doing new freeze plugs.

The risers I can't tell if they're drained.. At least it was all full of -50° RV antifreeze before the draining so any residual left hopefully would be ok.

 

[IslandExplorer]

 

[Scott06]

Yes, I did and you're right, one on each side. The two threaded plugs (about 1/2 I'm guessing) are just above the oil pan, one front right, other back left. Each Dumps out coolant, about 2 gallons each and noticed they are not connected as one went dry and then pulled the other and it drained a ton too. The J hose dumped a separate gallon plus at least. Crazy how much volume the block holds!

Each log has a center bottom plug I pulled and those seemed to drain out really well. All drains have been poked out really well previously including with small magnet stick while it was all dry and I was doing new freeze plugs.

The risers I can't tell if they're drained.. At least it was all full of -50° RV antifreeze before the draining so any residual left hopefully would be ok.

Riser drain into the manifolds. Sounds like you got it right as long as you drain and prob. Yes 4 gallons or so in the block