Im trying to find the correct hoses that go from the drive to an oil/ps cooler and then from cooler to water pump and also from the water pump to the crossover on the motor? If some fittings are threaded and some are slip on what do you use to convert one to another?

I dont understand the question. What are you trying to convert from threaded to slip on or vice versa? You can go to mercruiserparts.com and look up what year and model engine you have and see what you need.

Ok let me try to start over. There is a plastic barb slip on hose fitting on the inside of the transom(where the water enters the boat) that has a hose running to the oil cooler which has a threaded female end on it. And then out of the cooler (another female threaded end) a hose has to go to the water pump which has a plastic barb slip on fitting. Then out of the water pump (another slip on barb) to the crossover tube on the front of the motor which has a threaded fitting. How do you go from one end of the hose being a threaded A/N fitting and stainless braided line to a plastic slip on barb? Hope this makes a little more sense.

Sounds like what you are looking for is barbed hose fittings that you can thread into the oil cooler and water pump on the front of the motor so you can connect the 1 1/4" water hose to them correct?

The coolers and water pump are not an threads, they are npt pipe thread. The fittings you want can be found at cpperformance.com under cooling system parts.

Yes a barb that was threaded on one side would work for the drive to oil cooler run and from oil cooler to water pump. I am using a 90 coming out of the crossover and steel braided lines, and the steel lines wont fit on the water pump so is there some sort of an adapter to go from 1 1/4 hose to a -12 hose? Sorry for 20 questions here but Im starting from scratch on the cooling and Id rather get as much info as possible and do it right the first time...