jaybird

Ok, after all this, I talked myself into putting on the Merc pressure dump valves! This way no gauges, but no worries.

mr_velocity

I've run cross overs for the past 8 years, one boat used the pickups in the drives the other has offshore pickups. I run no T-stats, oil temp is only a problem if I don't get on it, so it's never a problem. On a long cruise it will run right around the 200 mark, when I'm on it never see anything more than 220. That is in the pan, after the cooler is stays well below that. I do have monster coolers on it. Water temp is always down, maybe 120 on a hot day. I've never had water pressure problem, ever. Water pressure is 18psi at 5600 rpm. At idle it's 5 psi. I monitor all temps and pressures all the time.

Been 5 years and the only problem I've had with these motors has been one vacuum leak in a Dominator and those damn fiber ropes in the CMI exhaust.

Now I have seen pressure problems on stock 500 EFI in a 36 Skater but I think that is due to the pickup built into the bottom of the boat.

RLW

I ran a crossover on my 468 Blower Motor. It had the bypass with an orifice installed in the bypass. Nothing more than a 1/2" pipe plug with a 3/8"hole drilled in it, jammed inside the hose. T-Stat had (3) 3/16" holes drilled in it.
Never had any water pressure problems with the bypass setup. I ran with the bypass blocked off and had all kinds of pressure. Too much, over 30 psig. I even had a dump, off the supply to the crossover, to bleed off excess water. Still too much pressure.
The bypass was the answer for my application. Motor ran about 155 degress at 3500 rpm. Maybe 165 degress at full throotle for short burst. Oil only got up to 200 degrees (indicated) at 3500 rpm. Just shy of where it should be. Had contamination from condensation when we tore the motor down. Had a Perma-Cool Oil T-Stat installed. Not sure if it was working properly. Plumbed it according to the instructions. Some people have good luck with them. I plan on using a crossover with bypass and T-Stat on my N/A motor. Want to try something different in regards to a Oil T-Stat setup. Possibly Merc, Canton, or Hardin Marine. Still investigating.
Russ

jaybird

RLW - I was told to put that 1/2 plug with the hole in it into my bypass hose too. One of my engines was overheating with the T-stat in, and over the winter they told me to try putting that restrictor in the bypass line. Strange how the other engine runs fine...

They said that water was leaving the engine too quickly, which didn't make sense to me. If water was leaving quickly, then new cold water should be replacing it therefore making the block colder?

RLW

Jay,
Maybe you had a bad T-Stat and it wasn't opening. Remember, my T-Stat had 3 holes drilled in it so water could flow and relieve any possible steam pocket/pressure buildup.
I could be way off base on that last comment as I am by no means an expert on the subject. Just relaying what worked for me.
Don't forget that you are introducing water to the downstream side of the T-Stat with a bypass. The orifice is a means off regulating the amount of water that sees that side of the T-Stat and what flows out to the exhaust. Too much water from bypass could shock the T-Stat into not opening soon enough.
Just throwing things out. It's all trial and error.
One more thing, I was running a 142 degree T-Stat.
It would be nice to know what these other members are running for T-Stat's.
Russ

jaybird

Not a bad T-stat, and did have holes drilled. I am going to test all my coolers next.

BTW - 142 degree thermostats, works perfect in the other motor.

Fuhgedaboudit

I run 140 t-stats, motors never run warmer than 135. We are goung to keep the stock set ups anyway, run recirc pumps and have no worries man! trouble will find you no matter what so dont go looking for it!!


A bird in the bush was the best time I ever had

Bobnoxious

Do not waste time with cross overs unless you like to keep track of a possible problem no temp, no flow, to much pressure, condensation in the oil. 5 min after I ran my new engine it blew a head gasket back in the garage working on the engine again. No one has the answer a lot of info try this do that but not a clear setup that works keep the merc setup and enjoy driving the boat not fixing it

Fuhgedaboudit

you guys are absolutey right...I will not be messing around with the factory set up...I plan to replace the raw water pumps with the new mercury 1 piece housing and new impellers, put new belts on, plugs, filters, all fluids( including transmissions and outdrives ) and we're good to go. Hope to be in the water 1st weekend in may for the season. We trailer this boat back and forth every weekend and its been a long winter...can't wait to get out there !