Water crossover issues
 

Has anyone experienced while running your engine on a test stand & on a garden hose, with a crossover system that uses a thermostat & bypass, The stb side of the engine & crossover pipe runs hot & the port side of the crossover & engine is cold. Cold water is flowing out the bypass to the exhaust. I am bypassing the seawater pump at this point & just running house pressure threw the system. There is no pressure build up in the engine at this point since there is no restrictions. I thought of removing the thermostat & blocking the bypass off but ultimately that would defeat the purpose of having a thermostat & keeping the engine temp well regulated. I have drilled 3 holes in the thermostats as well. Any thoughts??
https://cimg2.ibsrv.net/gimg/www.off...b42c079b93.jpg

Update: Just to add more input, Ive tried a couple different things. I removed the thermostat & blocked off the bypass hose. Ran the engine on garden hose full pressure. The temps all over the engine were rock solid, steady & consistent, but colder than I want to see. Next, I reintroduced the thermostat, which I did drill 3 relief holes, & bypass hose unblocked. Ran the bravo sea pump with a Hardin Marine SS body kit. Ran the suction hose into a 55 gal barrel of water so the engine would be as close to real time as possible. The temps on the crossover were similar results as it was on the garden hose but much less heat on the stbd side. So, the extra volume of water the sea pump delivered over the garden hose helped a great deal but, there is still a difference of about 10 deg, which im not liking. The lines I temporally made up from the rear of the heads is 1/4" hose. im going up to 3/8" just because, Dont know or think it will make much difference since the issue seems to start at the crossover on the front of the engine,(side to side) & not just front to back.

Thanks for sharing your results so far

I had similar experiences with my previous 292SR1 with twin warmed over Mark IV 454MAGs. I used the same cross over kit and fought with inconsistent temperatures from side to side, front to back, and water pressure issues.

Eventually, I ended up using a restrictor plate in lieu of a thermostat, Stuffing a brass plug with a 3/8” hole drilled in the middle within the front bypass hose, and adding two Independent small dump hoses from the rear two water ports on the intake manifold plumbed to the bottom of the Gil Offshore exhaust manifolds.

All of these modifications netted me Dead even temperatures and satisfactory water pressures throughout each engine. The biggest change what the bypass hose “restrictor plug”, this gave me even temps left and right on the stainless crossover tube.

Oddly enough, my first 223LS with a single warmed over 454MAG Gen VI Used the same kit and worked without any modifications.

distantthunder, Thanks for that input! Great info! What did you experience for water pressure issues? I have concerns with that as well. As of yet, I have no pressure build up but their not in the boat yet either. Ive ordered pressure dumps to have should I decide to add them as precautionary. Jury is still out there. How is your engine temp with a restrictor & what size did you wind up with? Removing the thermostat & blocking the bypass had the best results for me but I want to achieve 140 ish degrees if possible. If using a restrictor, is there really a need for the bypass hose anyway? Since the thermostat is no longer a door that has to open to let water pass threw. If the bypass is needed, say for extra water supply to the exh manifolds, or in my case the headers is there enough water supply to keep the headers cool under heavy throttle?.. On your 232, I wonder if the difference was related to the different cooling design between the Mark IV as compared to the Gen V & VI.

NautiB,

Unfortunately I do not recall my initial water pressure readings but I do recall conversations that I had with other members that deemed them excessive so I opted to remove the thermostats and replace with the restrictor plate, I tried to find the receipt for you but I recall using the smallest orifice in the kit that I purchased which reduced the pressure to about 5-10 PSI at idle and 30 PSI at WOT (if memory serves me correctly). With that resolved, I noticed that the starboard side of the crossover tube was considerably hotter than the Portside of the tube which I believed was due to the design of the inlet of the tube and location of the bypass (path of least resistance) it seemed the port side had less of a chance to get an ample amount of flow. Once I drilled the plug and shoved it into the bypass hose, both temperatures were dead even across the crossover tube. Slowing the flow through the bypass allowed for the water flow to increase in pressure and flow more equally through the two ports on the front of the block. I then recall having higher temperatures in the rear cylinders of the engine so I utilized the two ports on the back of the intake manifold to bleed off some of the water flow by relieving the flow via a small diameter hose to each of the exhaust manifolds of the Gil Exhaust plumbing it to the bottom elbow of the water fittings under the manifold. The water pressure differential between the intake manifold and the exhaust in theory would allow for a freer flow from the rear of the block and out while still maintaining a level of flow within the casting within the engine as it didn’t completely dump the entire stream by using the small diameter hose. Once the small dump hoses were installed, I saw even temperatures front to rear of the engine. I opted to plumb the hoses to the bottom manifold water fittings instead of the extra bung near the joint so the higher pressure water stream wouldn’t water jet a hole into the inner water jacket wall since the extra port location would have pointed the stream directly at that surface inside the water jacket.

I believe the engines were running a little north of 165F which would be enough heat to dissipate any condensation in the crankcase/oil.

All of this occurred over weeks of trial and error while concurrently battling a sticking exhaust valve on Cylinder 8 which was due to a failing Mechanical fuel pump. I may have an older post on OSO of this journey as well. Haha!

The kits Ive found offer 3 sizes. 5/8 3/4 & 1" ID holes. I guess its trial & error as far as what will work best as there are hardly any 2 systems alike. Id say your right on target about the design of the cross tube. It does favor the port side & then the bypass & finally the stb side which on mine, running the sea pump out of a 55 gal barrel is 10-15 deg hotter. I may try the restrictors & remove the bypass first. When I did it before while running on just the garden hose, the temps were equal everywhere across the engine & cross over tube, they were just cold. As long as the exhaust stays cool enough, that may be just the ticket for these engines. Ive already done the plumbing at the rear intake ports as you can see in my initial pic. That set up is only temporary. It will be finished in AN fittings & hose plus Im going to dump it in a thermostat riser block. Its ported just for that reason & seeing as there wont be a thermostat anyway, Im thinking it will flow straight out to the exhaust cooling hoses anyway.