I have a crossover i got from cpperformance that has the 1" bypass hose. When running the cold water from the bypass seams to be causing the tstat to close and engine temp rises to 250.
I was wandering if anyone has tried a y fitting in the bypass hose and ran it straight to the headers instead of dumping the cold water on top of the tstat?
Would this cause a flow issue in the engine if routed this away?
Looking for options, any suggestions would be appreciated!
THANKS

Wow sounds like these crossovers are more problems than they are worth. See my earlier post on my 540 running hot on the starbord head with a crossover newly installed. I am still asking questions everywhere I can, enen the outlets selling these things are not much help. I will enquire about your issues in my quest. Perhaps you can do the same for mine. Good luck. 1000+ hrs on the original merc water pump and no problems, change to the crossover now issues.

Ran X-overs for years, tried different sets to get the right balance of heat in the engine and cool manifolds as well. Finally went back to circ pump and newer style Merc thermo housing and engine temps are stable. For me, I was always either too cold or not stable engine temps. Water temp here swings from 60's to 95 plus. The bypass with the 1/2" bypass hose as sold by Stainless Marine worked best with 3 or 4 1/8" holes drilled in the t-stat flange, the holes are necessary to keep flow through engine and to stabilize the temps, without the holes the thermo cycles open and closed as the cold water from the bypass hose dumps down on the top of the thermo keeping it closed until it gets too hot.
The bypass set that uses the 3/4 or 1" hose from the cross-over to the thermo housing, in my case bypassed too much water such that when the engine got warm and the thermo opened, there was not enough pressure to push the water through the engine, it took the path of least resistance by going through the bypass. Keep in mind that in my case, I MUST idle out over and hour so I can't "rev" up the engine to generate more water pressure. Hence, I went back to the circulation pumps. Soon to have three sets of 2 crossovers with Thermo housings (enough for twin engine installation) with thermo housings for sale. Set one, no bypass, have to run without thermostat or with restrictor. Set two, the SM version with the 1/2" bypass hose. Set three, I believe it is the cp version with the 3/4" or 1" bypass hose.

ran mine for years 1/2 bypass, 140 stat, 4-5 1/8 holes drilled no issues, temp stable @ 150

Floyd,

We are the manufacture of the crossover assembly you would have bought from CP Performance. Please feel free to call us as you have something else going on that makes no sense to us. We have manufactured 100's of these units. The preferred bypass hose is 1" as to not create unnecessary block pressure. Your whole engine is plumbed with 1" hose. When you have a closed thermostat assembly and only a 1"2 bypass it creates multiple problems that people attempt to solve by then drilling additional holes in the thermostat. We will be more than glad to help diagnose some options?

Sincerely

You do have the stat in the right direction, right?
Spring to the intake side

How much did it cost you to go back to original setup? I'm thinking about doing the same. Having a hard time with 50 degree Lk Mi water. Are there used pumps around or did you go with new?

I've used that Hardin crossover for years. I don't see how putting water on top of the thermostat can cause it to close. The temp sensing coil is under the the thermostat. Perhaps corrosion or other blockage preventing normal water circulation. Crossovers usually work well as is but drilling a couple of holes in the thermostat does help to even out temp fluctuations.

I talked to hardin marine and the t-stat i got didnt have a vent hole for steam so they are sending me a new t-stat to try out.

I went back with all new stuff, by the time it was all over I guess about $900.00.