Supercharge Your 6.5 Diesel With a Boat Blower

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Whipple SuperchargerWay back in the early days before 1996 there were no turbo Hummers. N/A engines were offered all the way through 1998. The only available supercharger was the Whipple which cost around 5000.00 uninstalled. Due to low volume Whipple stopped producing kits for the Hummer. There really was no option for owners with N/A diesels until now.

The 6.5 diesel has always been a favorite for boats. There are companies that specialize in setting up these engines for boats with superchargers. Marine engines are built to take hours of full throttle running so they are heavy duty.

I received some feedback on my forum from Marine Diesel USA. Here's what they said:

We manufacture a supercharged marine 6.5L diesel engine based on the AM General 18:1 compression Optimizer. We supplied the supercharger kit for the H1 mentioned earlier. There is an aftercooler that is typically used in combination with the supercharger to lower the EGTs and makes a much more efficient package. We produce an 250HP and 300HP superhcharged model and average cruising RPM for marine applications is 3000 RPM and we don't have any issues with high EGTs. I highly recommend our supercharger kit for all your 6.5Ls. We also have the recalibrated injection pumps and marine injectors available. Marine Diesel

There are several differences between a marine and automotive 6.5L engine. In marine applications the engines are loaded much heavier than an automotive application. In marine applications typical cruising RPM is 2800-3200RPM and max is 3600RPM. For our marine engines we use a shell and tube heat exchanger that uses a combination of glycol and sea water to cool the block. Another difference is that the exhaust manifolds are water cooled.

Contrary to gas engines, most diesel engines, including the 6.5L, have no specific internal differences from a automotive to marine application. We don't build a turn key 6.5L for automotive applications as of yet. We can however supply a AM General 6.5L 18:1 compression crate engine complete with the recalibrated injection pump and supercharger kit for about $11,000 (250HP) or $12,500 (300HP). You could then switch over the pulleys, cooling system, electrical harness, ect. A turn key 250HP-300HP marine 6.5L engine runs from $18000-$20000.

Blower Mounted The Supercharger

One of my readers from Colorado sent me the following information on what he did. Because he lives around 5000 feet and regularly goes wheeling at over 10,000 feet the N/A diesel just wasn't doing it for him.

This is not super complete by any means but should serve as a good starting point for any of you owners that are good mechanics and good at tracking down the details. I strongly recommend you install an EGT (exhaust gas temp) and boost gauge.


I have a 94 2 door pickup with a 6.5 N/A diesel. The Supercharger and manifold are actually sold by These folks are based in Oklahoma and build boat motors based on the 6.5 optimizer engine. Jacked up Truck

  1. Get a 2 inch lift kit and start the lift on your hummer but don't bolt it all down yet. In fact lift your body up almost 6 inches using floor jacks. This makes working on the blower much easier.
  2. Remove dog house and engine cover.
  3. Drain the antifreeze.
  4. Remove intake manifold, oil pump drive and crankshaft engine speed sensor from back of the motor. Install a flush mount oil pump drive. Install new engine crankshaft sensor at the front of the motor. Move the wires to the new speed sensor and plug them in.
  5. Remove and turn the thermostat housing 180 degrees.
  6. Install a 165 or 170 degree thermostat so it clears the snout of the blower.
  7. Trim and modify radiator hoses. this blower is going to make some heat!
  8. Mount the new intake manifold and blower.
  9. Route the intercooler hoses from the back of the blower.Crankshaft Sensor
  10. Note: While the blower is off you may want to turn up your fuel. It's much easier when this whole thing is apart.
  11. Install new serpentine belt.
  12. Lower body back down on the new 2 inch mounts and finish the lift project.

The rest of the install is basically custom stuff now. Such as the intake tube to the air filter housing. I used a tube from an old dodge Cummins truck or you can fashion it from a pipe.

I had to modify the rear engine cover also.

To keep the cooling in check I added a couple of electric pusher fans. I also had to modify the engine cover so that the back of the blower and intercooler lines would fit.

Thermostat Housing Turned
The Thermostat housing is turned

Now put it all back together and make it run! The good people at have this version of the engine tuned up to 400hp.

Mine is not that radical. One thing I noticed from the startup is not a whole lot of smoke anymore. The sound of the blower is kind of cool and the engine response is right now!! It is nice to be able to cut through traffic and not be the slow guy in the right lane.

This install is for the most part a no brainier. Other than the speed sensor and electric fans no electronics.

Modified Radiator Hose
This shows the modified radiator hose.

Marine Diesel from Stillwater, OK has been super helpful with my truck. They now want to build a 400hp version for a show truck. they have different injectors and pump selection. Unfortunately my truck is a stock 6.5. Right off the bat I knew I had more power. The truck will accelerate going up hill.

Extra Cooling fans
Electric Cooling Fans

Modified Engine Cover
Modified Engine Cover

Boost is at 1 pound from idle.  Half throttle is about 6 pounds and %80 percent throttle is 9 pounds and mashed to the floor gives you 11 pounds. This is about the same as the stock Hummer turbo diesel. The EGT really climbs quickly.  I followed your instruction in the mounting of the gauges. 

Dodge Air Intake Pipe
Dodge Air Intake Pipe

CTI Air Intake
Relocated CTI Air Intake