Whipple Supercharger Install

A Relatively Easy Way to Dramatically Increase Horsepower

Author

Dan Duffer

Words & Photography

Ok, so you have your quarter-million dollar boat with twin 500 EFI Mercruiser engines for a total horsepower of just under 1000, but that just isn’t enough. What do you do? Well… there is one relatively easy way to dramatically increase horsepower, that’s right—a supercharger. On top of the power increase you get that cool unmistakable whine that will cause any wrench head to notice. This particular install is a stage 3 Whipple supercharger which will add approximately 240 hp per engine; in essence, we are adding a third engine.

Of course there are kits available for many different engines, but since we are installing this on a 500 EFI MerCruiser engine, I’ll start with a few warnings about this particular engine. Mercury recommends that the top end of these engines be rebuilt every 250 hours. If your engine is due, or close to due for this service, I strongly recommend doing this first. Even if you have 50 hours to go it’s a good idea to get it done since you will have the intake manifold off for the install. The other big concern is the water pressure in the block. Along with the more explosive burn that creates the extra power comes more heat. You will want to install block pressure gauges to keep an eye on this. The reason for wanting to watch block pressure instead of just temperature is that the higher the pressure, the higher the boiling point of the water. If the pressure gets low enough that the water can boil, it will create air pockets in the block.

All right, with all that said, let’s get started. First, it is a good idea to disconnect the batteries. Time for the mass destruction. Now you need to pull the distributor out in preparation for removing the intake. It will help to put the engine at 1 top dead center before doing so. It will be much easier to put it in the new intake if you have that reference.

It’s time for the intake disassembly. Start this by draining all the water out of the engine. You will find blocked drains on either side around the engine mounts. If you do not drain the engine first you will spill water into the lifter valley when you pull the intake. Next you will need to remove the upper plenum which is held on by 12 bolts. A number of connectors and vacuum lines need to be disconnected first.

Once you get the upper plenum off, it’s time to remove the intake. I find it easier on the 500 EFI to remove one of the fuel rails to remove the wiring harness. You will need to remove all injector connectors, engine coolant sensor connectors and anything else that runs across the top of the intake. At this point the harness will push off the back of the engine. Now remove all of the bolts that secure the intake and gently pry the intake free of the silicone.

Now is a great time to lay out all your parts, organize them, and check for missing pieces.

You will need to remove the crankshaft pulley; the new setup will be installed later.

Next remove the idle air control motor from the factory intake and install it in the new intake. Be careful, you will need to reuse the screws and o-ring.

Now you will need to remove the cooled fuel system from the engines; these are no longer going to be used with the new setup.

Also remove the fuel filter at the back of the engine.

And all the other fuel system components including lines and the factory water separating fuel filter.

Now remove the stock coolant temp senders and the intake air temp sensor, these will be installed on the new intake.

Next remove the mechanical fuel pump and put the supplied block off plate in its place.

The circulating pump also has to be removed. Also remove the stock belt tension pulley bracket.

Next install the stock coolant temp sensors in the front of the new intake. It is a good idea to put a small amount of gasket sealing compound on the threads. Install the stock intake air temp sensor in the back of the intake.

Find a good location to install the supplied block dump and intercooler dump. Make sure the location you chose is above the water line.

Check the inside of the boat for clearance, then mark and drill with a hole saw. Apply a marine grade silicone to the seal surface of the thru hull fittings and install them. Use enough silicone so that is squishes out on all sides; this way you will know it is sealed.

Clean the intake manifold gasket surfaces and check that new gaskets fit properly. You may have to trim the gaskets around the tray flanges at the bottom.

Apply a thick bead of RTV silicone to the front and back surfaces of the block that contact the intake.

Install the new gaskets.

Gently set the intake into place; make sure the gaskets did not slide.

Torque all new bolts to proper torque in the factory recommended sequence. Install the O-ring material that comes with the kit into the groove that runs around the top of the intake. Put a light amount of grease on after installing it.

Put the intercooler assembly in the intake manifold.

Use Teflon tape on the threads of the –10 fittings for the intercooler and install them on their proper side. The long one goes on the starboard side. Tighten the sides evenly. Now install the billet spacer that allows the blower clearance for the distributor. Use the same O-ring material.

Install the new thermostat housing with the 5/8 restrictor.

Once installation is complete, you will see two extra screw holes. These holes need to be plugged with supplied bolts.

Cut the tape off of the wiring harness just enough to route all the connectors to the proper locations.

The map sensor will now be mounted to the back of the pulley bracket so you will need the map sensor extension harness.

Next install the new crank pulley into the factory crank pulley and install to the balancer. Put a small amount of Loctite on each bolt and torque to 35 ft-lbs.

Now install the stainless crossover tube that takes place of the circulating pump along with 4 spacers and billet belt system bracket. Install the distributor into the new intake and connect wires. Be very careful to get indexing right the first time.

Before installing the supercharger check to make sure you won’t have any boat clearance issues, you may have to do some trimming.

Time to put the bad boy in place. Install O-ring material into groove on the bottom of the supercharger and apply grease. Then set charger in place and reinstall throttle linkage as it was when you first started. Torque bolts to 35 ft-lbs.

Plug in the throttle position sensor and the eight injector connectors.

Plug in the idle air control motor; depending on the application, you may need an extension harness.

Install the front idler plate using the new hardware and spacers. The collar slides over the front of the supercharger. Tighten the setscrew that clamps to the supercharger after bolts are tight.

Install blower pulley using hardware supplied.

Connect map sensor extension wire to new map sensor on the back of the front plate. It’s time for plumbing the new fuel system. There are two ways of doing this, the preferred way is to rout a return line all the way to the fuel tank. The problem with this is that most tanks do not have a place for a return. In this case the return has to pass through a cooler and return before the fuel pump. This install did not have provisions in the tank so we had to use the cooler method.

Start by assembling the fuel pump, filter and tee (if required).

Find a good location to mount the pump. It is best to mount it below the tank but is not always possible. Mount it in the desired location using supplied brackets. If it is mounted above the take you will need a check valve to keep the pump primed when the engine is shut off.

Then find a good place to mount the regulator. The regulator is installed on the return side; keep that in mind when selecting the location.

If you do not have a return all the way to the tank, install the fuel cooler on the return side.

The best location for the cooler will be outlined in the manual.

Now the fuel lines can be made. All the supply line must be –10 and all the return lines are –6.

Next the fuel pump needs to be wired. Install the new relay that uses the signal from the factory fuel pump connector, and rout wires. Follow instructions very carefully.

Find a clean location for the intercooler pickup. Make sure that the location is always going to be underwater and is not directly in front of the drive. Drill a hole and install with a good marine-grade silicone that is for below-water line use.

Next are the intercooler hoses. Rout in desired location and cut to length. Use supplied press lock fittings and connect to intercooler, pickup and dump.

The block dump is connected to the two small elbows that are located at the back of the intake where the cooling passages in the heads meet the intake. Install those hoses and rout to block dump location.

Then the cooling system hoses need to be cut and routed. There will be a new piece of hose that will connect to the stainless crossover.

Install stock PCV valve and hose on port side valve cover and rout hose to intake.

Install breather on starboard valve cover.

Next there is a vacuum line that needs to be routed from the intake to the fuel regulator, and one from the intake to the new map sensor.

Install the factory 6 rib-grooved idler pulley on new bracket and install the new belt.

Now fill the supercharger with the supplied oil. Fill only until you see oil in the sight glass on the front of the supercharger; do not over fill.

Fill only until you see oil in the sight glass on the front of the supercharger; do not over fill.

Install the supercharger belt and adjust the idler pulley so the tensioner has the correct amount of travel.

The one last thing to do is set up the throttle linkage. This will be different for each boat. Follow directions to ensure that the adjustment is correct so the throttle position starts at fully closed and will achieve wide-open throttle.

Well, that’s it, from here you will have to follow the specific instructions for the engine that you have. There are some setup procedures that are very important. Good luck.