2 ? 3 ? OR 4 Stage water pump?
 

what would be the best and why and what is the best way to plumb them......


supercharged,innercooled, and bell housing coolers.....

Re: 2 ? 3 ? OR 4 Stage water pump?
 

Do two water pickups. Preferably transom pickups. One will be dedicated to the engine with a mascerator type strainer. The second pickup will go to a mini mascerator type strainer. This way, the water will be cut off when the boat is off plane. This will prevent the fuel from condensing on the cooler. I would use a stock merc water pump with stock merc oil coolers. This way you can use preformed hoses and the merc brackets. When they are custom painted you get a nice clean installation. I know KE makes a multi-stage water pump, but has anybody ever really needed one? A stock waterpump is nice because you can get a impeller just about anywhere.

Re: 2 ? 3 ? OR 4 Stage water pump?
 

Most high performance builder use a 2 stage. One going to each bellhousing cooler then each bellhousing cooler has a line running forward to a dual intlet crossover. You will need a bellhousing that has an inlet and outlet for each cooler. You can also have a bung welded into each cooler in you only have one outlet in each.This what I did this winter.

You can also have a two stage water pump that has one outlet that feeds the oil coolers with a single inlet crossover.This is the normal merc 900SC configuraton.
In retrospect I would probably go with the second option if your not already plumbed with a dual inlet crossover. I spent over $1500 on two new crossovers and stainless braided lines to plumb them.

Also KE dual stage water pumps use standard merc impellers.

Re: 2 ? 3 ? OR 4 Stage water pump?
 

Having a seperate water pickup for the intercooler has a host of issues I can not get comfortable with. For one you will need a blow off valve to control the water pressure spikes or risk the possiblity of blowing the cooler. Second problem is a big problem, no water in the intercooler and it will get real hot and likely crack with the introduction of cold water when you take off.


I use a two stage pump. One stage for the engine and one for the intercooler. I also use a Stainless Marine intercooler sea strainer just before the intercooler. It has a fine mesh filter to prevent small bits plugging up the cooler.