Feeling stupid. Merc 4.3L closed loop cooling system?

[sledman11]

Picked up a 1995 Larson 19" with a 4.3L . Boat needs floor repair. I decided to try starting the boat just to make sure it ran okay before I invested time and money into fixing the floor and seats. Boat started fine and I ran it for probably 3 or 4 minutes on the hose. After that I went to clear the water out of the manifolds, engine block and power steering cooling. When I pulled one of the drain plugs on the block I had green antifreeze coming out. I quickly put the plug back in and started looking the motor over for a heat exchanger. I did not see one. Is the heat exchager built into the exhaust manifolds/risers?

Started it again and started pulling holes off the small manifold that is on the front of the motor just to see what lines were raw water and which ones were antifreeze. Raw water was coming up from the power steering cooler and feeding both exhaust manifolds up high the manifolds. The bottom connection to the manifolds is pumping green antifreeze. Water pump on the front of the motor was pumping antifreeze.

Can someone set me straight on what I have in the boat. Just want to understand the system and to make sure I get it winterized properly. I live in the northeast and only boat in fresh water. I have winterized many boats but none with a half or full closed loop system.

Thanks in advance.

Don

 

[alldodge]

Without more info on the motor (serial number) I would guess that it was winterized with regular AF or the Sierra stuff. It didn't run long enough to clear out the green stuff (thermostat did not open) so its just mixing a slight bit of fresh water, and this will not clear out all the green

Mans are not HX so unless there is one up front, behind or along side the motor, its open cooled

 

[scoflaw]

do you see a tank and a radiator cap ?

 

[Scott Danforth]

if you dont have a 4" diameter, 18" long black tube with a square bump on the top and a radiator cap sitting on top the front of the engine, you do not have a freshwater cooled engine.

 

[sledman11]

Without more info on the motor (serial number) I would guess that it was winterized with regular AF or the Sierra stuff. It didn't run long enough to clear out the green stuff (thermostat did not open) so its just mixing a slight bit of fresh water, and this will not clear out all the green

Mans are not HX so unless there is one up front, behind or along side the motor, its open cooled

The serial number is 0F067587. I did not see a HX or a tank / radiator cap. I had the same thought about someone using regular antifreeze to winterize but figured I would of flushed that out. I ran it for 3 to 4 minutes the first time and then ran it again today for probably 10 minutes. Considering how cold it is here that probably is not enough time to get the thermostat to open.

Thanks everyone for your input.

 

[Bt Doctur]

post some pics of the engine , but with no heat exchanger you need to drain everything out before the freeze

 

[Lou C]

Given what you are saying the block and heads are probably still full of AF and the exhaust is prob full of water. Drain the exhaust manifolds and raw water intake hose. I'd fill the raw water intake hose with -100 marine af till it runs out the drive intakes (drive down) and then just crank the engine for like a sec (don't start it) and that will get AF into the Alpha impeller in the drive. You can fill the manifolds with marine AF if you want but that's optional, just get all the water out. I'd have tested the AF that came out of the block. Make sure it does not freeze in a freezer set at zero or whatever is the coldest temp you get.

PS Sierra PG antifreeze is green just like the old school toxic ethylene glycol AF. I use Sierra mixed 50/50 to winterize my boat because its non toxic and is much cheaper than the -100 I used to use.

 

[achris]

....till it runs out the drive intakes (drive down)

If you get AF running out of the water intakes, then your impeller is completely shot... It needs to be replaced.

and then just crank the engine for like a sec (don't start it) and that will get AF into the Alpha impeller in the drive.

Which you just filled up and confirmed by AF running out of the intakes. And cranking the engine will not fill the pump, it'll empty it... :facepalm:

Chris.....

 

[achris]

OP, does your engine look like this?

 

[tpenfield]

Got a camera/smartphone to take some pictures of the engine? Tell us more about the floor that needs to be replaced. Seldom is it just the floor

 

[Lou C]

Unfortunately true! Most of the time the tops of the stringers will be soft/rotted too.

 

[QBhoy]

Lou c has the likely answer here. I’ll agree it’s likely still full of antifreeze from previously and it’s either not taken in water when running briefly or the t stat hardly opened.

 

[tank1949]

Picked up a 1995 Larson 19" with a 4.3L . Boat needs floor repair. I decided to try starting the boat just to make sure it ran okay before I invested time and money into fixing the floor and seats. Boat started fine and I ran it for probably 3 or 4 minutes on the hose. After that I went to clear the water out of the manifolds, engine block and power steering cooling. When I pulled one of the drain plugs on the block I had green antifreeze coming out. I quickly put the plug back in and started looking the motor over for a heat exchanger. I did not see one. Is the heat exchager built into the exhaust manifolds/risers?

Started it again and started pulling holes off the small manifold that is on the front of the motor just to see what lines were raw water and which ones were antifreeze. Raw water was coming up from the power steering cooler and feeding both exhaust manifolds up high the manifolds. The bottom connection to the manifolds is pumping green antifreeze. Water pump on the front of the motor was pumping antifreeze.

Can someone set me straight on what I have in the boat. Just want to understand the system and to make sure I get it winterized properly. I live in the northeast and only boat in fresh water. I have winterized many boats but none with a half or full closed loop system.

Thanks in advance.

Don

If floor or deck is rotten or weak, stringers and transom may be too. Before ripping out floor, I suggest tapping transom, especially around drain area. Off season is the best time to work on your money pit, at least it has been for my pit... Pray transom is solid on your I/o.

 

[Scott Danforth]

if the floor is rotten, the transom rotted long prior. the floor is always the last to rot.