Can anyone explain to me why you would install a water crossover kit? I am guessing by photos this is installed in the place of your water circulation pump. How does the water get pumped? what are the advantages and reasons for doing this to a marine engine?
Circ pump is just that. It will not pump, only circulate.
Some drives have a water pump in the drive. Use a circ pump with it. Small blocks
Most drives do not have a water pump. Uses a raw water pump belt driven on the engine. No need for a circ pump. Big blocks.
Saves HP and looks cool.
[ October 14, 2003, 07:06 PM: Message edited by: Infomaniac ]
The circulation pump does not directly affect the overall cooling capacity of your system. That is mostly determined by the amount of cold water that comes out of the lake and goes through your engine, as determined by the "sea water" or "raw water" pump. Doesn't matter if it's in the drive (Alpha) or mounted on the engine and driven by a belt (Bravo), it does the same job either way. Whether or not you run a circulation pump is more determined by how much control you want over the core temp in the block and heads. The factory Merc system uses the circulation pump, a distribution manifold, and a thermostat to route only as much cold water through the engine as is necessary to keep the block and heads at some constant coolant temp. Excess cold water is routed directly to the exhaust along with the discharge water from the thermostat housing. When you install a crossover, you lose the circulation pump and the distribution manifold. In its simplest form, the crossover system routes all water through the block, heads, intake, and then out to the exhaust. A variation of that system uses a bypass and a thermostat to mimick the constant temp operation of the factory system, but without the circulation pump. I did not find the crossover system with thermostat to work very well because of large temperature swings as the thermostat opened and closed. Maybe others have had better luck, but I ended up ditching the thermostat and now I just run the motor cold (it's clearanced for it). Advantages of the crossover system are simplicity, light weight, and potentially improved cooling capability because of guaranteed 100% cold water flow through the block all the time. Drawbacks are that the motor will likely run cold most or all of the time.
Hope that helps...
-brian
I like to run the circulation pump. I have a sbf and even with the unlimited amount of cooling flow from the jet pump, the best way to regulate even flow through the engine I've found is with a t-stat and curculation pump. Motor comes up to temp quick, runs 165 F (everywhere in the motor)with a 160 tstat all day long, wether idling, wot, nos, or whatever. I think it can be hard on a motor to have a lot of fluctuation in temp and/or dump cold water constantly to the front and have it hot at the rear where it exits.
I also preheat the incoming water through the bottom of the exh manifolds (raises incoming temp about 35 deg's) and then let the tstat determine how much goes into the engine and let the rest go out the exhaust.
jd
PS. Only problem doing it this way is the damn motor lasts too long (10 years now with 400+ lbs of n2o) and I have to pull it out while its still running good to put in the new motor I'm building. Its hard to make the wifey understand why I needed the new one when the old one never breaks.
[ October 14, 2003, 08:42 PM: Message edited by: quiet riot ]
Good point about the preheating. I run through an oil cooler first, but with headers I don't have the option to run through the exhaust before the block. Wish I did because I usually have a hard time getting more than 120 deg on the gauge even in summer!
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