which coolant to use

[donaldm]

New to boating, I bought a used 05 boat with a 5.0 mercruiser which has a heat exchanger I guess thats called a "closed cooling system" the coolant recover bottle is at full but the collant level in the exchanger is below filler neck and what little I see in the tank looks like water (no color like green or orange coolant) Should I fill the exchanger tank or will the system pull coolant in from the recovery tank at start up? I asumme that somebody might have added just water to the system (not sure) so I would like to emty the coolant or at least add coolant to the exchanger but what type antifreeze do I buy green or orange? the owners manual reffers to "Tube ref no 122" on page 65 what is tube 122? thanks for any help.

 

[Don S]

Re: which coolant to use

If you are going to drain the system, use what ever kind you want, they are all ok for use in those engines.
Scan page 65 and show us. I doubt anyone here has exactly the same manual as you do.

 

[donaldm]

Re: which coolant to use

I dont have a scanner Im reading from a "Mercury operation, maintenance & warranty manual" by mercury. I think there talking about an additive to the coolant part 92-877770k1. I found the adult sticky section and that helped but still not sure what "tub 122 is. By the way im confused is this ford merc engine or a chev small block (5.0) thanks so much for the help . . . Ill learn this stuff soon.

 

[havasuboatman]

Re: which coolant to use

the newer Merc. motors that have the closed cooling systems use the orange engine coolant. Unless you completely drain and FLUSH the system, keep using that type. The two types of engine coolant DO NOT MIX which leads to insufficiant cooling of your engine.
Keep an eye on your engine temp. I would be very curious as to why your coolant was so low the resivour was completely empty.
When you fill the coolant, us the resivour to do so. Run it to operating temp, let it cool and check it again.

 

[WizeOne]

Re: which coolant to use

It's most likely a GM/Chevy 305 cid. Merc quit using ford engines 20? years ago. Why, I don't know. I think the ford 302 was hard to beat for weight, performance and reliability. Plus you didn't have to stick your head back under the rear deck to change the points.

 

[havasuboatman]

Re: which coolant to use

It's most likely a GM/Chevy 305 cid. Merc quit using ford engines 20? years ago. Why, I don't know. I think the ford 302 was hard to beat for weight, performance and reliability. Plus you didn't have to stick your head back under the rear deck to change the points.

Yes, it is a GM motor. The displacement will be listed on the top of the engine. (air spark arrester housing, Plenum, etc.)

 

[Don S]

Re: which coolant to use

It IS a small block Chevy, the last Ford was in 77.

"Mercury operation, maintenance & warranty manual" is what they call ALL of their owners manuals and have for years. And yes, they are all different since things change on each engine.

 

[donaldm]

Re: which coolant to use

once I fill the exchanger coolant tank can I safely start the engine (for a limited time)and run it up to temp 170-180 without connecting any other out side water supply . . . is there a water pump (like in a car) that will move the exchanger tank coolant throught the engine block?

 

[Don S]

Re: which coolant to use

once I fill the exchanger coolant tank can I safely start the engine (for a limited time)and run it up to temp 170-180 without connecting any other out side water supply . . . is there a water pump (like in a car) that will move the exchanger tank coolant throught the engine block?

ABSOLUTELY NOT !!!!!!
You must have water to the engine in order to cool the exhaust,a prevent the raw water pump from self distructing. You also need to have the outdrive DOWN before starting the engine.

There is a water pump (like in a car) but it's called a circulating pump. Since you have a closed cooling system, you may have an engine mounted raw water pump, or one in the outdrive. More details from you are needed to find out which.

 

[45Auto]

Re: which coolant to use

I wouldn't use the orange stuff (Dex-Cool) in anything. First thing I did when I got my boat was completely flush the system and change it over to the green stuff (Prestone). There's been lots of problems and lawsuits in which GM has been forced to pay for repairs related to Dex-Cool. See this webpage, http://www.dexcoolsettlement.com/index.php3, particularly Group C, which is supposedly caused by air getting into the system through a leaking radiator cap:

Group C Covered Repairs: Repairs necessitated by cooling-system sludge, including cooling-system flush, heater core repairs, water pump repairs, or radiator cap replacement. ?Sludge? refers to a rust-like material that can form in the cooling system and whose formation is related to use of Dex-Cool.