Please share more about your other mods to increase power, sounds interesting!
Start with "Chapter_04_Fuel_System.pdf":
Originally Posted by Polaris NEVER remove or attempt to remove the tamper proof devices from the full-load fuel adjusting screw or the high-speed throttle limit screw on the fuel injection pump and governor assembly. These adjustments have been made at the factory to meet all applicable emissions regulations and then sealed.
• NEVER attempt to make any adjustments to these sealed adjustment screws. If adjustments are required, they can be made only by a qualified fuel injection shop that will ensure the injection pump continues to meet all applicable emissions
regulations, and then replace the tamper-proof seals.
Once you've decided to ignore these warnings, you can adjust the Yanmar fuel injection Pump and injectors, just need somebody with experience on this facet of Yanmar diesel engines.
The max fuel limiter is on the back of the pump, the end opposite the input shaft. Once you get the tamper resistant sleeve off, you remove the acorn nut, loosen the lock nut, and turn the screw CCW to increase fuel. You need a 17mm and a 10mm wrench. A full turn is probably safe for a stock engine, but it's best to have a egt gauge installed if you're going to go that far. If you haven't bypassed the hp spring on the transmission command lever you can add all the power in the world and you won't see any difference.
The command lever is on the hydraulic pump, it is what the cables connect to. The command lever moves the pintle lever and the pintle lever moves the swashplate inside the pump to control displacement. There is a spring between the command lever and pintle lever. Under normal conditions and light load the spring does not compress and the levers move together. Under heavy load (going up hill or accelerating quickly) the back force on the swashplate increases and compresses the spring. This allows the pump displacement to automatically be reduced without the command lever or treadle pedal position changing. The purpose is to prevent engine bogging or stall under load. Polaris calls it the hp spring. If your machine has the update the spring tension will be adjustable. If you adjust it for maximum tension you should be able to get the engine to bog down slightly under load. To disable it completely you can drill and tap the command lever and install a bolt against the pintle lever to effectively lock the two together. If you do this you will be able to feel the swashplate pushing back through the pedal when the two speed valve shifts, and you will probably be able to stall the engine unless you've added significant power. Mine with the turbo will just drop a few hundred rpm going up the steepest hill.
As for egt, it's hard for me to say since I'm not really a diesel mechanic. I've read 1200 degrees is safe. Mine will hit 950 when climbing a hill at 8 psi.