XR6 Propshaft on V-King

Hi Randy, 

I recently bought a 1996 Merc 150 XR-6 to put on my V-King and I have been told that some of those motors came with a 2-piece propshaft, depending on the year.  I'm not sure what kind lower unit is on my motor, but I'm pretty sure it is whatever lower unit Mercury was installing on XR-6 motors back in 1996 (I think it's the original).  I don't think it's the CLE because trailing edge of the skeg is swept back, not straight up and down.   It also has a built-in speedometer pick-up (a small notch in the leading edge of the LU) and I believe it has 8 water pick-up holes on each side (but I'm not 100% sure of that because the motor is off being mounted to my boat). 

I want to install a nose cone and LWP so I can surface the prop to what works best for the V-Kings (around 3/8" below pad seems to be the sweet spot), but I have been told that if I have the 2-piece propshaft and I go higher than 1-1/2" below pad, I will break something.  My mechanic said that my lower unit is the same as was used on the 200s and that I shouldn't worry about it too much, but I don't completely understand what that means and I don't want to install a nose cone and LWP if surfacing my prop that much will break my lower unit internals and drop my 28" ET to the bottom of the lake.  For now, I have threaded the top two water inlet holes on each side of the lower unit and plugged them with allan screws so I can surface the prop somewhat. 

Do I have the 2-piece propshaft?  If so, how much can I surface it before I really start risking some form of damage?  What would you suggest I do?  Without the nose cone & LWP, what do you think the blow-out speed of my set-up will be?  Will I ever need a nose cone & LWP for this boat and motor combo?  I am not opposed to changing the prop shaft and installing a nose cone & LWP if you think it would be worth it, so if that's your suggestion, please let me know what prop shaft I should install. 

Thanks again for your help! 

Forbes

 

Forbes, 

Putting a stock XR6 on a V-King doesn't require a nosecone or LWP gearcase. 3/8" below the pad with only 150 hp is excessively high. You will find it will not carry weight such as a passenger in the front seat very well and acceleration will suffer. 3/8" below the pad will work well with about 250 hp, but you will need to be at least an inch and a half below the pad with the limited power you have to get satisfactory performance. You will still be surfacing the propeller, but it is all about leverage. Jacking the motor up and throwing water in the air is not the way to go fast. The 28 ET on your XR6 with the stock gearcase, will run 80ish mph. My recommendation would be, install a torque tab on the stock gearcase and make sure you run solid motor mounts. As long as you are installing the motor mounts, replace the exhaust tuner with part number 41941. This is the exhaust pipe off a 2.4 Bridgeport. It will give you a "free" 10+ hp or so.The stock jetting is fine as the pipe has less backpressure than the stock 13" long pipe. With a 150hp motor by adding a LWP nosecone you will be adding drag due to the longer surface area. You will also increase tail lift. These will not make you go faster but the other way around. Unless you have 200hp or more the cone is a waste. If you do decide to put a cone on it and jack it up to the pad you can run the propshaft from a 2.4 Bridgeport. Have the dealer look up the propshaft for serial # OC175710. This will get you to the correct parts book. 

Randy

 

 

Please submit whatever questions you have to IHRTechTalk@yahoo.com.  All questions and answers selected will be displayed on this page as they come in.  Note: though all boaters are welcome, priority may be given to I.H.R. members.  Randy can not be held responsible for any advice given.  Though his information and expertise is second to none, he has no control over what you do with your boat.  It is up to you to boat safely and act responsibly, and his advice is only to be used as a guidance for your high performance boat/motor of which you are the one responsible for the risks involved.

Thanks,
Mark C.

 

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