temperature climbing at higher RPMs

If you are using a screw driver to tighten the hose clamps then your not getting them tight enough use a 1/4 drive ratchet to tighten then and recheck all clamps fr the pickup to the rwp

That is a good troubleshoot list from skidim..
First and foremost you definitely have an issue that should be addressed. I have a couple times tried to convince myself this was normal behavior or simply a gauge issue and a couple times damaged the engine through overheating.   You are on the right track with the new strainer, if the old one was questionable it could infact pull in a little air under higher rpms. When you are putting it in be sure to check your transmission cooler for blockage, a little seaweed or other debris on the upwind side of that baby will do exactly what you are describing. Personally I like to disconnect the hose from the RWP and back flush that cooler with the garden hose if I suspect an issue. After that be sure all clamps are tight and no hose ends are cracked, again it doesn’t take much of an air leak on the suction side of the rwp to cause an issue at higher rpms.

Assuming none of that helps you, and your rwp is in good shape then I would not discount the circulation pump as a source of trouble. I have had a relatively new one have the impellor loosen up on the shaft and cause the same symptoms and eventually a true overheat. As long as the rwp is working the manifolds will still see water but without the circ pump the engine won’t necessarily see all that it needs.

Also the thermostat in the boat is two weeks old and there wasn't any blockage in the housing when I installed it. The hose that was bulging was old but was replaced last weekend. It wasn't really badly bulging just a little when the pump was pushing a lot of water through it. Is it possible that bad manifolds or risers could cause a restriction in the system? I'm still getting plenty of water out the exhaust on both sides and haven't burned up any exhaust hoses.

William, a water hose bulging seems like a little bit of a red flag to me. It could be that it was just old, but it does sound like a possible restriction further down the line. Possibly pieces of an old impeller in the thermostat housing.

Cooling system terminology is a little counter intuitive. When people say "Fresh Water" cooled, they actually mean cooled by a captive coolant. This is maybe a carryover term from salt water boating.

When people say "Raw Water" cooled, they actually mean cooled directly by the lake water which is actually fresh, go figure.

Both systems use a raw water pump however. In the instance of a "fresh water (coolant)" cooled boat, the raw water pump pumps water through a heat exchanger, which is like an automotive radiator, but uses raw water to cool it rather than air.

In a raw water cooled system, the raw water pump cools the motor directly.

One more confusing thing, the part that looks exactly like an automotive "water pump" is called a circulation pump on the marine system. It circulates either coolant or the raw water that the raw water pump has brought up from the lake.

WLM 1986 wrote: And to answer BuffaloBFN I'm pretty sure the Ski Dim guy knew the boat was raw water cooled because I was buying a raw water pump in the same order

Skidim knows more about these boats than I do; I was trying to figure what wires may have gotten crossed.

Both systems use a RWP.

Thanks for all the input guys, sorry it took so long to reply back I didn't have my computer working. And to answer BuffaloBFN I'm pretty sure the Ski Dim guy knew the boat was raw water cooled because I was buying a raw water pump in the same order, but thanks for wanting to clarify. So I have a new thermostat on the way now and I even ordered a Sherwood Strainer for the boat, The old one was an off brand and was in questionable condition even though I could not find any leaks. I'm not sure that I was completely clear on the first post about the temperature climbing. I usually Wakeboard behind the boat and we run about 2,200 rpm and 22mph, At this rpm the temp gauge stays steady as i would expect right around 185 F or so. But when we are Slalom skiing the RPM is 3200 to 3400 and the temperature keeps climbing like the cooling system can't keep up. I know my raw water pump is good as well as all the plumbing on the way to it. I'm pretty sure the circulation pump is moving enough water because I can see the hose coming off it expand when the RPM rises, I also had that hose tear last week and checked the flow when I was putting the new hose on. So I guess my question is could old manifolds and risers possibly be plugged up enough to slow waterflow out of the engine and not let enough fresh water in? I have checked them with the IR heat sensor gun and they aren't much hotter than the thermostat housing, but are a little hot to the touch. They are basically the last piece in the cooling system that is old and that I haven't replaced yet since owning the boat. Again thanks to everyone who takes time to read and answer my posts, It's a big help. I have been reading these forums since I have had the boat and most my questions are just answered by reading previous posts. Now that I have delt with quite a few problems on this boat I am hoping I can pass on some knowledge to other people with the same boat.

WLM 1986 wrote: the replacement was a 160 degree at the recommendation of the Ski DIM technician due to the fact the boat is run in fresh water.

I wonder if they meant fresh water cooled? As in closed cooling system?

very doubtful because you still are getting a good supply of cool water from the rwp, but your temps are pretty normal and i would probably go back to the 140 thermostat, and it will with the 140 normally run in the 160 range