Adding Closed Cooling after 300 hours
- Thread starter gustaf
- Start date
toofast
Active member
I'm sure others will chime in but I'm fairly certain that's a fairly comprehensive retrofit I'm sure it can be done but it's not as simple as a few nuts and bolts here and there
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AllDodge
Well-known member
It can be done, but I would not do it with a motor with more then maybe 50 fresh hours on it, 100 tops. The scale inside the motor will continue to flake off and can clog up things like HE and thermostat. Others have done it and gotten away with it, others have had to pull the system apart and get it cleaned out, but 300 hours is a bit past my thoughts.
I have done a conversion to closed cooling on my Formula 330 w/ 7.4's. The boat spent 16 years (740 hours) on Lake Winnipesaukee, NH prior to my purchasing it and it had open cooling all that time. I was bringing the boat to Cape cod to run in the salt.
Although the age and hours were on the high side, I figured it would be better than letting the salt have a go at the engine cooling system. To confirm my thinking, I took a look at the thermostat housings and what I could see of the engine block internals with the water pump removed. They looked really good, with only powdery surface rust . . . no scaling.
Along the way, I learned that a cooling system flush with an oxalic acid (wood bleach) solution and then a neutralizing flush (baking soda), then a plain water flush would be a good preparation to convert to closed cooling. It will remove much of the powdery rust within the engine block passageways.
So, I recommend you do some inspection of the thermostat housing and then, if all looks good, do an acid flush to remove the internal rust. Then you should be good-to-go with closed cooling.
Keep in mind that you will want to do salt-away treatments of the heat exchanger on an annual basis as the salt build-up will block the cooling passages inside the HE over the course of a few years. I actually took my cooling system apart after 4 years of use and did some cleaning of the passageways.
To add to the comments on installation, yes it is not a slam-dunk and will take a couple of long days, if you DIY. If not, I'd expect to pay upwards of $1,200 for installation labor per engine.
Also, I'd recommend going with the FULL closed system (block and manifolds) rather than the HALF (block only) system. Figure about $1,000 per engine for the closed cooling kit. I used the SJE kit, but SeaKamp and SJE are both fine aftermarket kits. I also found that the thermostat configuration on the kit was not to my liking and I modified the t-stats to compensate.
PM me if you want some details on the installation.
Although the age and hours were on the high side, I figured it would be better than letting the salt have a go at the engine cooling system. To confirm my thinking, I took a look at the thermostat housings and what I could see of the engine block internals with the water pump removed. They looked really good, with only powdery surface rust . . . no scaling.
Along the way, I learned that a cooling system flush with an oxalic acid (wood bleach) solution and then a neutralizing flush (baking soda), then a plain water flush would be a good preparation to convert to closed cooling. It will remove much of the powdery rust within the engine block passageways.
So, I recommend you do some inspection of the thermostat housing and then, if all looks good, do an acid flush to remove the internal rust. Then you should be good-to-go with closed cooling.
Keep in mind that you will want to do salt-away treatments of the heat exchanger on an annual basis as the salt build-up will block the cooling passages inside the HE over the course of a few years. I actually took my cooling system apart after 4 years of use and did some cleaning of the passageways.
To add to the comments on installation, yes it is not a slam-dunk and will take a couple of long days, if you DIY. If not, I'd expect to pay upwards of $1,200 for installation labor per engine.
Also, I'd recommend going with the FULL closed system (block and manifolds) rather than the HALF (block only) system. Figure about $1,000 per engine for the closed cooling kit. I used the SJE kit, but SeaKamp and SJE are both fine aftermarket kits. I also found that the thermostat configuration on the kit was not to my liking and I modified the t-stats to compensate.
PM me if you want some details on the installation.
