I have a 1979 360 Tournament Fisherman that has the original 1 3/8 shafts and my insurance company is requiring I increase the shaft diameter to 1 3/4. Any suggestions?
Can you offer to upgrade to stronger shaft material? Otherwise, thinner cutlass bearings in the shaft struts will save the struts. New shaft log seals, machine or replace props, new flanges to connect to transmissions.
That is odd - Chris Craft did upgrade to 1 1/2" in the early 80s, I think when they made the transition to Mercs/Velvet drives. If you are still running the CC/Marine Power 454s with Paragons, the Paragons would be the weakest point in the drive train. Was that something that was recommended in a survey? Most other boats of that time period and size (Viking, etc.) ran 1 3/8" shafts.
Boat was originally gas. In 1994 they installed a pair of 350 hp 3116 Cats with 1.5 to 1 gears. I think I can get by with 1 1/2 shafts I'm not sure if the struts will hold cutlass bearings for 1 3/4 shafts.
I'm wondering if the diesel's torque are why the insurance is wanting to upgrade the shafts? I had a 33' Egg Harbor with 350HP Crusader's that came out of the factory with 1.25" shafts. I never had a problem running that boat for years. My 36' Sports Cruiser was repowered from the 427's to small block Mercruiser fuelies but with the same 300hp rating. I'm still running my 1 3/8" shafts.
Yes, the high torque of the diesel engine is the issue. Once you change the RPM at which the engine makes it's rated power to a lower RPM the safety factor drops (for a given gear ratio)..
Can you offer to upgrade to stronger shaft material? Otherwise, thinner cutlass bearings in the shaft struts will save the struts. New shaft log seals, machine or replace props, new flanges to connect to transmissions.
What engines and gear ratio do you have?
That is odd - Chris Craft did upgrade to 1 1/2" in the early 80s, I think when they made the transition to Mercs/Velvet drives. If you are still running the CC/Marine Power 454s with Paragons, the Paragons would be the weakest point in the drive train. Was that something that was recommended in a survey? Most other boats of that time period and size (Viking, etc.) ran 1 3/8" shafts.
Boat was originally gas. In 1994 they installed a pair of 350 hp 3116 Cats with 1.5 to 1 gears. I think I can get by with 1 1/2 shafts I'm not sure if the struts will hold cutlass bearings for 1 3/4 shafts.
I'm wondering if the diesel's torque are why the insurance is wanting to upgrade the shafts? I had a 33' Egg Harbor with 350HP Crusader's that came out of the factory with 1.25" shafts. I never had a problem running that boat for years. My 36' Sports Cruiser was repowered from the 427's to small block Mercruiser fuelies but with the same 300hp rating. I'm still running my 1 3/8" shafts.
Pretty sure it has something to do with the safety factor being less than 5.
Yes, the high torque of the diesel engine is the issue. Once you change the RPM at which the engine makes it's rated power to a lower RPM the safety factor drops (for a given gear ratio)..