>>The 11 HP does have a stepped crank end. Is that going to be a problem?
Depends on how far back the step goes. If the 1” part sticks out far enough for the 8hp pulley to line up with the lower pulley then it’s ok. Some of the stepped cranks are long so may hit your cover. You could saw it off or make a hole for the protrusion.
I had to modify the belt cover fit to accommodate 11hp Honda style OHV I put on a 924050 8hp body. The engine crank pulley was higher than the 8hp so I cut a U shape along one side of the belt cover. The cut for the U legs ran along the edges of the belt cover and the right angle to the legs was cut at the low section of the belt cover. That made a flap connected at the top of the cover. The flap was then bent up to make the top higher for pulley room. The flap was fixed there with black duct tape. Cut cleanly and placed well it held the flap and stayed in place with vibration, cold and getting wet. Without being told that the cover was cut and taped a person would not notice it.
>> Should I take the pully off of the HM80 and use that instead on the one that is existing on the 11hp motor?
You could use either as long as the 11hp pulley will work with the existing belts. If the 11hp is a bit bigger diameter it will increase the rpm of the system i.e. augers and impeller. That would be nice.
You have not said what your model is but I’m guessing an ST824 924xxx series and will have a single cast double V of two different size belts. Your Murray probably won’t match.
>>You mentioned taking the existing pully off of cam PTO and not using that pto at all. Is that ok to do? Will the motor lose any power if I dont use that pto?
Your 8hp does not have a PTO does it? There is nothing for it to drive. Without the drain from the PTO the crank will have that power available. No problem that I know of. I know of a number of transplants engines with PTO to non-PTO snowblowers.
>>I really dont have any problems with the HM80 but, I got the 11hp for almost nothing. I figured getting a little more power is a good thing.
It will get you a slight distance increase in normal snow and go through packed more easily with about the same distance as normal snow. Wet snow will not be a problem. For bad slush it will pump out ice cylinder blanks that fall to the ground without breaking.
One thing to consider is going with a bigger pulley. Your 11hp will still rotate at 3600 RPM but have more power and torque. You could work out the numbers to get the impeller at 1300 to 1400 RPM. That would be nice. You’d have to make even more belt cover room. In that case you could cut it in two and tape in a 2 inch piece to extend the top section.
>>Can you think of any real disadvantage I will have with an 11hp motor on a 24 inch path snow blower?
The base was meant to have a bigger engine but that was usually balanced with a bigger/wider bucket. It will handle and feel like you have a big engine which it is but won’t be tough to use.
Doing the swap will be a challenge the first time but after you’ve done it swapping back will be easy. You could try it for a while and if you don’t like it change back.