Water Temp To Low ???????
 

Hello,

I ran my boat the other day after the engine was dynoed and I'm seeing some very odd temp readings. My temp doesn't even register untill you hammer it for a couple of minutes and it goes to about 140 max. As soon as I go back down to idle it returns to about 110. I know this can't be good for the engine. There is a whole heck of alot black soot all over the transom and outdrive top cap as well.

My system consists of a merc sea water pump feeding a cross over to the block. The t-stat housing has a 160 degree marine t-stat in it.

I think the cold temps are making the engine run really rich. I'm running in 49degree lake water, but the t-stat should be regulating some what??????

I thought about putting some type of restriction before the pump , but i dont want to cook my engine.

Does anyone know of a device that could keep more of a constant temp, other than closed cooling or a circulating pump.

Any ideas or help would be great


Brian

Re: Water Temp To Low ???????
 

I had the same problem last year, and just got it fixed last week. I took the thermostat out, boiled in water with a temp gauge and it opened right at 140 like was on the thermostat. Scratched my head :eek: to make a long story short,,, I replaced the thermostat and problem went away.
Temp gauge went back to 140 (still not high enough for me)
I will never know what was wrong with it.

Re: Water Temp To Low ???????
 

Questions:
What kind of water pressure are you seeing? Do you have a bypass from the crossover to the thermostat housing?

I sure hope you are running a bypass and a pressure relief valve!! Trying to run a motor with a crossover and with a thermostat without a bypass, or relief valve is asking for a milkshake, and or a fried exhaust, or both, when the thermostat is closed especially!!
===
From listening to your post, it sounds like you probably don't have a thermostat installed. That's exactly how my crossover behaved without one.
Thermostat's increase block pressure big time.

If you want to run a thermostat with your crossover, you need three things for sure.
1. A water pressure gauge.
2. A water bypass from the crossover to the thermostat housing.
2. A water pressure relief valve, made by Merc Racing. Don't have the part number handy...These fit on the intake hose after all the coolers and before the crossover and dump the excess water overboard through a dump.

Problem with crossovers:
1. No thermostat = no need for a bypass, good water pressure, but far too low temps, too much water through exhaust if running junk mufflers (exception is GGB extremes).
2. Thermostat without bypass and without a pressure relief valve = potentially fried exhaust and milkshake motor from too much water pressure and no exhaust water when the thermostat is closed. High water pressure exists even when the thermostat is open!
3. Thermostat with bypass and without a pressure relief valve = good exhaust water volume, potential milkshake motor from too high water pressure.
4. Thermostat with bypass and with pressure relief valve = all good.
Kent

Re: Water Temp To Low ???????
 

The water temp shouldn't be an issue. You should be more concerned with oil temp to prevent the milkshake and condensation in the oil.

There are several decent priced Oil thermostats on the market.

Re: Water Temp To Low ???????
 

I have crossovers in my new Mesa 700's and my water temps arent getting over 100 degrees. I am concerned because Im now going to run it in 40 degree water instead of the 75 degree water in Florida. I questioned Laz on this issue and he stated to check the valve covers for excess condinsation after running, and if there is he will reduce the size of the hose to restrict water flow and therefor increase water tempature. No need for thermostats in his opinion

Re: Water Temp To Low ???????
 

Pantera is right. Oil temps are everything.
I've been through the whole crossover thing...

Another fellow and I were trying to make a thermostat work with the crossover and he milkshaked his motor TWICE on the dyno from head gasket failures. He installed a water pressure gauge and was seeing 35++ psi.
So was I before we found and installed a relief valve. I was lucky because I just blew hoses off before the gaskets failed.

The problem I had is that even with the oil thermostat on my HP500, the oil temps took FOREVER to come up, without a thermostat. I never saw any water temps until a WOT run. The oil temps took about 10 miles of slow plane speeds to see 180 on the gauge....
It's real hard to have to run that far before you can go fast!!

After the thermostat installation, the water temps come up to 140 in about 1/2 mile and the oil temps are up to 180 in less than a mile! They hit about 210-220 at WOT....The motor sure seems happier now, too. It may have been running a little lean with the cold temps...

Just my experiences...
Kent

Re: Water Temp To Low ???????
 

Thank you for all the replies, I appreciate it!!!!

I think that I didn't clarify myself properly. Let me try it again.

The system has a stainless marine cross over with bypass and a marine 160 degree t-stat. I does take a heck of along time to get the Oil Temp(Not Water Temp) to register in Cold Lake George Water. The engine is a small block running a merc raw water pump for cooling the engine and exhaust.

I forgot to ask the guy who dynoed it what the water psi was, but he said that he had to restrict the water flow before the pump to get it to make temp on the dyno.

Is that what I have to do to get the temp to at least stay at 140 0r 160.

i was thinking about putting in a new 180 stat and seeing what oil temps I'm getting. (Am I wasting my time or would a pressure relief valve help me?)

Brian

Re: Water Temp To Low ???????
 

The cross over is the reason for the low temps. The sole reason. I have one on my N/A engine and it never builds temp until I get to warm water. The engine running cold isn't the worst thing in the world. What really matters are your oil temps. That must be correct. To get the oil temps to rise faster install a thermostat. Permacool makes a nice one. This will bypass the oil cooler until the temps rise. It works very well. If you are running rich, then try leaning the engine out a bit. Sometimes they do need a little adjustment in the boat due to different loading. You don't need a water pressure gauge, but you do need to check that pressure. Too much water pressure will result in a blown head gasket. Keep the pressure under 25psi. I have mine around 10psi which is proably a tad too low. The excessive pressure would also be caused by the cross over but can also be caused by an aftermarket exhaust system.

Re: Water Temp To Low ???????
 

Brian, That is exactly what Laz told me to do if I have condensation build up.. Restrict the water to see higher water temps. I also run on Lake George

Re: Water Temp To Low ???????
 

I am having the same milkshake problem. What if I remove the crossover and install the circulation pump? What would the downfall to that be?

Re: Water Temp To Low ???????
 

Do not restrict inlet water flow (to pump).
Control water flow on the discharge of the pumping system.
Problem then becomes water pressure.
Control pressure with a pressure relief device.
Control oil temp with a thermostatically controlled device.
I have been through all of this.
I use the Mercury Racing water pressure relief valve and the Mercury Racing Oil Temperature Contolled Oil Filter mount.
I use a crossover with a bypass and a 142* T-stat with (3) 3/16" holes drilled in the T-Stat.
The bypass has a 1/2" brass pipe plug with a 3/8" hole drilled through it, jammed in the bypass hose. This is installed on a N/A 540.
No Problems! Good Temps across the board.

Re: Water Temp To Low ???????
 

I checked my water pressure at the block and at the top of the intake manifold. Both of them were 2-3 PSI at idle and about 8 PSI at 4000 RPM. From these numbers it does not appear that water pressure from the crossover is the problem. Any other ideas?

Re: Water Temp To Low ???????
 

These readings were done while on the hose. However our shop hose is at a fairly high PSI for that it has a booster pump on it.

Re: Water Temp To Low ???????
 

Water pressure on the hose is alot different than water pressure while underway.

Re: Water Temp To Low ???????
 

I just completed a test. 30 min with the exhaust going out the transom and got milkshake. 60 min with the exhaust going out the prop, and the oil looks great. The test was done on the hose, 700 rpm. I have done this test 4 times now and every time I get the same results. Any ideas? I know that this is completely opposite than what one would think with reversion happening when the exhaust has a clear shot out the rear and not when it is going out the prop. Any ideas??? THANKS!!!!

Re: Water Temp To Low ???????
 

RLW, you are right on the money!
Listen to him.

The only thing I might add is that it's a good idea to plumb the relief valve =after= all coolers, so these have the benefit of the water volume...

Plus, I believe with any boat, a water pressure gauge is a good piece to have. It tells you a LOT about the health of the cooling system.
Kent

Re: Water Temp To Low ???????
 

> I think the cold temps are making the engine run really rich

If the cold temp did anything, it would be to lean the mixture... that is, assuming a cooler block = a cooler intake manfold.

On my brother's 588 Merlin II, I'm looking to run a thermostat, but there's lots to consider before jumping in. It's been suggested I work the problem from the oil temp side (coolant by-pass thermostat on the oil-cooler), but I'd like to do both... but WATER TEMP first.

So far, I've done nothing. Waiting to learn more before I jump

jrc in SC

Re: Water Temp To Low ???????
 

Is yout motor fuel injected or carbed? I know a stock 502mpi has to reach a minimum temp on the coolant sensor or it stays in warm up mode(runs extra rich). Procharger gives you a signal conditioner to "trick" the computer into thinking its warmed up. My 502 and my 540 (current motor) both run around 100degrees to 120 max (in warmer shallow water). I am using a crossover,no stat. I was skeptical about the low temps with 502 at first(i was always under impression you got rapid cylinder wall wear under a certain temp) but when i tore 502 down at 200 hours it had no ridge and no appreciable scuffing or taper,Smitty
P.S.-tyler crockett set efi program this time on dyno to account for low temps when operating so i have a spare signal conditioner if someone needs it for a really fair price.

Re: Water Temp To Low ???????
 

Good info!! where would you u sugest plumbing a dash mounted water pressure gauge then?