Joe Warren
Well-Known Member
- Joined
- Nov 29, 2003
- Messages
- 8,241
Different Boaters ask me every day what engine to Power Up or Repower there Twin or Single engine Hydro with. After a Year of Hard Racing my #1 Choice is CMB RS101 The current production engine comes with a flat Top Piston that gives the added material on top of the piston for added Durability. Purchased new this engine still requires Grooming. Head Bowl Volume MUST be Increased for High Nitro Racing (50-60 percent nitro use) Normally the intake rotor disk clearence is Decreased by machining off the front of the crankcase & the intake & exhaust timing need to be double checked especially if they are going to be ran in a Twin Engine Application Boat kit. Large pipe pressure fitting needs to be installed into desired Exhaust pipe & Large Fuel Tubing used thru out the Entire Fuel System. A Clean Fuel Filter & Clean Fuel Needle are a MUST! Also the Water Cooling Head on this engine is Way Over the Top.... After removing the Red cooling Water jacket from the engine you will notice a divider ring on the crankcase. there are 2 holes that allow water to flow from lower area to the upper area of the cooling head ( in rear area right above ex port). We plug one of these holes with a 4/40 set scerw. This allows the engine to make some heat on its own & you dont have to starve it for fuel to make heat..... A Mac`c Marine p/n 1395 & 1394 Pipe have been found to be the best performing pipes. Mark Bullard & Steve Wood can set your Engine up Properly. Both are on this web site & can be contacted. However the 91-VAC is Very Good out of the Box Race Engine & has the proper head Volume & clearence for High Nitro use. it uses the Rotor intake valve & no clearence adjustments are necessary. VAC 91 Headers & VAC 91 pipes work very well on the Current Blue Head 91 VAC engine. Both engine need large pipe pressure fitting installed into the desired pipe & large fuel tubing to feed the Engine & Fuel Demand. I have Personally found that the RS101 is a Little more work to Get it Right. But It Will Swing More Prop & Cup. VAC 91 props for a Twin are 1667 - 6.5 - 6.9 depending on the Pipe & the age of the Boat kit they are installed into. RS101 Props 1667 - 6.9 - 7.5 Depending on the Boat Kit (New or Older) & Pipes Used. Many Advantages in Boat kit mfgering are Currently being made to allow for Added Ride Heights & different Sponson Angles to allow Todays Engine to Excell at a level never seen Before.
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