1998 4.3 GL Head Replacement

[Lou C]

The whole problem with running AF in is this: because of the way raw water cooling works if you don’t drain the block first you can’t count on the thermostat staying open long enough to get all the water out. So it really only makes sense to fully manually drain & back fill with AF if you want to use AF. And if you’re in the northern climes I would not use -50 or -60, they start to get hard at about 10-15*F. Use -100 for trouble free self winterization. I will mix up my own GP mix with Sierra antifreeze when I can find it. Cheaper than the -100.

 

[drew_caplan]

The whole problem with running AF in is this: because of the way raw water cooling works if you don’t drain the block first you can’t count on the thermostat staying open long enough to get all the water out. So it really only makes sense to fully manually drain & back fill with AF if you want to use AF. And if you’re in the northern climes I would not use -50 or -60, they start to get hard at about 10-15*F. Use -100 for trouble free self winterization. I will mix up my own GP mix with Sierra antifreeze when I can find it. Cheaper than the -100.

This, I ran AF through the muffs and didn't push out enough water. I also used a -50 AF. Upon further inspection even though the motor looks pristine from the outside, inspecting all of the water jackets it is very corroded inside and and there are large flakes falling offside the ports. The motor is 24 years old and clearly raw water and winters have taken the toll on these passageways; combine that with my mediocre way of winterizing we ended up with a cracked block. It was a lesson for me but I also feel kinda good about putting in a brand new motor essentially in a beautiful boat that my family enjoys to get a lot more life out of it.

I am going to pull the Cobra SX drive, replace the bellows, new gaskets and a freshen up so I am feel good about heading into the waters this summer to get my 9 year old up on the wakeboard; that right there is a priceless moment for a parent. Plus, the pup needs to be on the water again soon...

 

[Scott06]

This, I ran AF through the muffs and didn't push out enough water. I also used a -50 AF. Upon further inspection even though the motor looks pristine from the outside, inspecting all of the water jackets it is very corroded inside and and there are large flakes falling offside the ports. The motor is 24 years old and clearly raw water and winters have taken the toll on these passageways; combine that with my mediocre way of winterizing we ended up with a cracked block. It was a lesson for me but I also feel kinda good about putting in a brand new motor essentially in a beautiful boat that my family enjoys to get a lot more life out of it.

I am going to pull the Cobra SX drive, replace the bellows, new gaskets and a freshen up so I am feel good about heading into the waters this summer to get my 9 year old up on the wakeboard; that right there is a priceless moment for a parent. Plus, the pup needs to be on the water again soon...

when you get the new engine in and go to winterize in the fall just drain it before using AF.

 

[Lou C]

Better yet add a half closed cooling system. If I keep my old boat long enough to need a repower there is no way on earth that I’m leaving it raw water cooled. At 68 years old I am done with pulling out the rear seats to get at the block drains. That’s the right way to do it but after 20 years of that, I’ve had it. Plus, raw water cooling is just a lousy system on engines designed for pressurized antifreeze!
Also West Marine who sells all different kinds of antifreeze does not recommend the -50 or -60 in climates that get real winter. Put a gallon of it in your freezer & see what happens. It doesn’t expand but it does get hard. I wouldn’t want that in a raw water cooled cast iron engine!

 

[Lou C]

Go onto west marines' website, they have a tech article on antifreezes and tell you what to use for your climate. Here -60 would be adequate, because we never get below 0*F, but if you get below zero, -100 is the only thing to use, IMHO.
I have a refractometer and mix up my own Sierra PG antifreeze; 50/50 with water gives -26* freeze protection. Way more than adequate for here and a little more than half the price of -100.

 

[Donald0039]

I think the whole concept of using the 5 gal container of antifreeze connected to the outdrive via muffs is questionable even with an outdrive with a impeller in the lower unit. The directions say to run on garden hose water until the engine is at operating temperature (thermostat open hopefully) then switch to antifreeze from the 5 gal container. You have got to hope that before you run out of antifreeze, enough of it has gotten into the block so the block will not freeze.

The only safe way is to drain block, manifolds via drain plugs and fill the block directly with antifreeze via a removed hose or thermostat housing.

Or closed cooling.

 

[Scott06]

I think the whole concept of using the 5 gal container of antifreeze connected to the outdrive via muffs is questionable even with an outdrive with a impeller in the lower unit. The directions say to run on garden hose water until the engine is at operating temperature (thermostat open hopefully) then switch to antifreeze from the 5 gal container. You have got to hope that before you run out of antifreeze, enough of it has gotten into the block so the block will not freeze.

The only safe way is to drain block, manifolds via drain plugs and fill the block directly with antifreeze via a removed hose or thermostat housing.

Or closed cooling.

For sure. Marinas that successfully do this on hundreds of boats are using a large tank with huge amounts of PG, checking for dilution.

the avg guy doing 5 gal is not enough run time, and on the hose with cooler water in spring and fall it is tough to really get the engine hot.

I do use this method on my old 2 stroke jet ski, but I am running 3 gallons through a 800 cc engine with no thermostat to ensure there is no mixing.

 

[Lou C]

The thermostat functions as a gate valve allowing water in the block to exit but it will only do that if the engine generates enough heat so that the water stays above the set point of the 'stat. And on a cool fall day idling with cold water coming in via the water hose that may not happen.

 

[Donald0039]

The thermostat functions as a gate valve allowing water in the block to exit but it will only do that if the engine generates enough heat so that the water stays above the set point of the 'stat. And on a cool fall day idling with cold water coming in via the water hose that may not happen.

There is typically a bypass opening so even if the thermostat is closed some coolant flows by.