closed cooled ?
 

can someone explain why mercury closed cooled engines have restricters in the water flow to the tail pipes 525,600,700 s

On the 525 motor, some restriction is needed on the starbord collector to equalize water flow from the heat exchanger, and keep the headers on both sides aproximately the same temperature. On this motor, I think they are restricted too much.

On the 600sci and 700sci, the tailpipes are restricted to force water thru the whipple type innercooler.

I personally think that there needs to be more water flow to the 600 and 700 motors. There are lots of people that have had smartcraft water pressure issues because of merc's water setup on these motors. These proplems are usually solved by installing a seperate water pickup and strainer for the innercooler, then opening up the restrictors in the tailpipes.

Chris

Do you mean resonators inside the exhaust hose by the tail pipe? http://www.boatfix.com/merc/Bullet/00/00_13.pdf

No.. we are talking about the water restrictors in the tailpipes that control water flow leaving the cooling system. Parts 14 and 15 in this diagram of a 600sci exhaust system.

http://www.mercruiserparts.com/Show_...lpipe+Assembly

Chris

heres my problem when im running 1,2 footers I over heat, the motors take turns my transom mount adjustable pickups cool the motors going to large sea strainer, imco drive pickup go,s to inner cooler. when this happens I have to stop shut down start right back up it cools right down I have496 base engines with wipples 810 hp 7lb boost this happends at all speeds Does the sea pump need some back pressure ,when I lower my scoops water pressure gets way over 30 psi MY scoops are 2 ichs above pad on the angle of the keel and carved to direct water this problem does not happened in flat water it seams like the gulp of air gets traped in heat exchanger .I have been chasing this issue sinse I installed cmi,s

You should be using the drives for the engine water and use the transom pick ups for the intercoolers. That is how I run it and I have no issues at all.

When you are in 1-2 waves, you are introducing air into the system because there is not a consistant flow of water to the pickups on the transom.

Smitty is correct.

You should have the drives feeding the engines, and the pickups feeding the innercoolers. On a closed cooled motors, mercury racing suggests 30-50 psi as normal running water pressure at wot.

On a smartcraft equiped motor, if water pressure drops below 26psi, with the motor above 5200rpm, the computer will throw a fault code. If the water pressure drops below 21psi with the motor above 5200, the motor goes into guardian mode, and will reduce power.

Remember... on closed cooled motors, the engine is not seeing any water pressure from external sources. Water flow is regulated by the restrictors in the tailpipes, and/or the restriction in the innercooler. The block is running antifreeze, and the only pressure on it is caused by the circulating pump, on the front of the motor.

Chris

P.S. I typically have water pressure in the mid 40's at wot.

do you have closed cooling

no 6 boats all use pick ups not the drive so what do they do

I have cmi headers ,install 2 years ago could never touch them ,also have 5 inch heat exchanger so this year we added the pickups thinking that it will run nice and cool come to realize that the headers didnt have any restricters I looked at all mecurys closed cooled motors so I added some ,still messing around with pressures now I can touch my headers also I have gauge set up too . I do think I needed the restricters allalong Ill be testing this week end and lowering the scoops