Cooling Problems

[GEOO]

I'm stumped??
I couldn't get my second fresh water cooling system to work. I tried everything. I'm sick of having cooling problems so I installed a crossover raw water system, and guess what!! Still cooling problems.
Here's what happens:
Start engine up run's fine from idle to 3500- 4000 rpms. Engine temp stays 140-160.
As I increase speed above 4000 the engine starts to increase in temp up to 190 and still climbs. If I slow down the temp stays at the high temp 180-190. If I slow down to an idle the engine stays at 180-190. If I turn the engine off for 10-15 seconds and restart the temp drops right down to 140-150.
This happened every time I run above 3500-4000.
Oil temp stay low 180-200 never climbed.
Water was always pumping out of the exhaust.

GEOO :( :confused:

[Woodsy]

GEOO,

The one thing missing is time. How long does it take to get to the high temperatures? Have you overheated before? You might have a blocked or restricted water passage in your block, or it could be an easy fix like a blown headgasket. I am assuming you have replaced all of the original culprits... water pump, thermostat, kinked hoses etc...

Woodsy

[Looped]

Could it be a flaky temp sender unit that’s giving you false readings?

Just a thought,
Craig

[TORYSMINX]

I actually had this problem in my 16 footer.
This could be totally different but I changed the thermostat and then ran a new sender unit. Things worked out great ever since.
I am wondering if I am going to have the same problems with the new motor. I had her on the stand for about and hour and was getting 175 degrees but I was not running a thermostat. didnt big grizzly say that running a little hotter can increase some hp? If it is going over 195 I would be concerned.

I am by far no expert but as Woodsy said start with the basics..

good luck and I am sure I will be talking to you in the future.

Tory

[Jamesbon]

GEOO,
Is your head and block combination one of those where steam holes have to be drilled in the head/block surfaces?

Nate

[Forrest]

I would think that it must be some restriction to water flow somewhere or to a lesser extent, air trapped in the engine cooling system. Are you using a thermostat or a flow restrictor or nothing? Is the temp sender mounted in the intake manifold, or is in one of the heads? If it's mounted in one the heads, like Nate said above, make sure that the steam holes line up with the associated holes in the head gasket, but also make sure that the head gasket does not block any of the cooling passages between the block and the heads. Also, if you don't already have one, pick up one of those hand-held laser temperature readers and check the temp at different places on the engine. That may help pin point the problem without having to take everything apart.

On a side note, I had a pencil zinc the was mounted in an aluminum intake manifold break-off and got lodged in the water circulation pump on one of my engines sometime back and I played hell trying to find the overheating problem. The trouble was that I was looking in all of the "conventional" places for the problem. Finally I pulled the circulation pump, opened up the back and there it was.

[Jamesbon]

Oh yeah, if you're using a block mounted circulation pump in conjunction with the raw water pump, make sure the circ. pump is being spun in the right direction.

[GEOO]

I'm running a crankshaft mounted raw water pump only.
Woodsy32:
The engine heats up with in a few minutes after running above 4000 rpms. Overheating has been a problem. It seams like some type of blockage?? The head gaskets are new. Passed a preasure test. All new hoses, pump etc.
The crossover system has a thermostat and a bypass for the exhaust.
The temp sending unit is in the intake manifold on the starboard side.
Nate:
The engine has the correct head gasket, head & block set up for cooling passages.
The starboard side seams warmer then the port side.
Forrest:
Good idea with the hand-held laser temperature reader. It seams like something may be lodged in the starboard cylinder head??
I'm taking out the thermostat, installing a restricter and taking off the bypass tube.
If this doesn't work I may need to pull the starboard head??
GEOO :confused:

[Jamesbon]

Maybe the by-pass is allowing too much water to flow to the exhaust manifold, hence not enough to cool the block?? (not sure if you've thought of this)

[mattyboy]

Geoo,
sounds like a gauge or sender problem, temp in engine is not going to drop from 190+ to 140 in 10 seconds especially if the engine is off, sounds like the gauge is stuck,I'm old school did ya tap on it? sometimes things need to be coaxed, when you cycle it (turn off and on) the temp seems normal right? maybe try and shut it off and on in less then 10 seconds see what it does, my boat shows signs of false overheat runs at 190 but after a run at speed when returning to idle gauge goes to 210-220 for a few minutes then goes back to 190 ( was explained to me has the hot water rising slowly in the engine after a hard run) but all the time the water is flowing it is still cool enough to put your hand in. This doesn't sound like that.
If it were a blockage the temp would keep rising even a long runs under 3500rpm just thinking outloud know, hope you get this problem licked. we can't have our shootout winner sidelined for too long
good luck
Matt

[Formula Jr]

If the oil temp holds steady at 180-200, you have a water temp sender problem. Tryed one of those inferred readers once, could not make heads or tails of the readings.

[Blewbyu]

I used to have a 460 Ford that did the same thing,and would still pump water at high rpm (tho a bit less).After weeks of grief,found it to be a suction hose that had delaminated on the INSIDE ONLY-not apparent from the outside.It would flatten as soon as I opened the secondaries,any time I tried to cruise above 3800,or any time I throttled up suddenly from cruise.Sure was a cheap/easy fix,but only way to find it was to replace hose starting at the lowest suction point.
Good Luck!
Blewbyu

[Blewbyu]

GEOO-I've not seen a marine engine WITHOUT a recirculation pump.Is this common among Donzi owners?Do you think your raw water pump has the cajones to suck AND recirculate the water? :confused:

[GEOO]

Mattyboy,
The engine gets hotter when it's off. When I restart it drops right down. If I turn the engine off for a second then restart it stays hot. New sending unit. And new replaced sending unit. It' hot!!
Madpoodle,
After I find the problem I might have to play with restricters to even out the temp.
Blewbyu,
Hum!!! I checked all the hoses. Replaced a few. Then are all wire reenforced, but maybe the insides are bad ??? Good Idea!!!
I don't think water pressure is a problem, at 70, 80 & 90 mph the water pick up scoop on the transom would build enough water pressure with out the pump. And the engine doesn't cool off when I slow down.

Thanks Guys, GEOO :confused:

[BigGrizzly]

Check the suction hose first, then the pressure. I had a pressure hose that came apart inside and ballooned up and clogged the internals.
Great talking with you to day. Looking forward to seeing you at the Donzi rally.

Randy

[Blewbyu]

Geoo-NUTS! I forget that there IS ONE guy on this registry that DOES have 70/80/90 mph available to build water pressure on an X-18!
Do give the hose thing a try-mine had the spring inserts in em too-collapsed anyway,between the spring loops.Soft hose can move around like a rat! I dissected the hoses as I took them off.......

[Moody Blu']

hmm, the symptoms geoo is having sound just like mine.

I was thinking about this, if one of the hoses collapses, that would mean that the impeller runs dry until you slow down and then the pressure drops enough for the pump to suck water back in it.
soo. what I am getting at is that maybe after runnning the boat a couple times and the temp starts to rise (collapsed hose)it eats up the impeller, which in fact causes another problem which makes it more difficult in figuring out what the over heating problem was in the first place.

I sort of know this because, when I first put my boat in the water I had an overheating problem ,from the start(with a brand new impeller) I took the pump off the boat and found an impeller that was torn up(the impeller was 4 days old)-there probably is still bits and peices of impeller in the block , but the water outlet seems to be even(no clogs).
so when I put the 10 year old impeller in the boat it seemed to run better. but it still overheated.
I have a topic on this same WOE.(up and down down and up arrrgghhh)

geo, you and I need to untie and try to figure out our overheating problem.

I thought it was my timing , but I checked my timing with a timing light, I even went as far as to change the timing curve( I thought maybe the ignition was too retarded(no pun intended)at 2500-3500 rpms and that was why it was overheating)
I change the timing curve today and it did the same thing. overheated, after a couple of mid to wide open runs.

It really makes me cringe when I see the temp needle of my new gauge go over 220 degrees.

:o
come on guys lets solve these probelems!!!

I am really glad there is a place like this to help battle against the beast of our hobby.
:D

[BigGrizzly]

Sky, if you even start the engine without priming the waterpump and have conatant water flow that will cause the impeller to fail early. This is no jetski.

[Moody Blu']

bg my water pump primes it self, the water from the outdrive actually runs nto the boat when I take the suction hose off of the water pump.

In conjunction with what bg said. my hypothesis is that if the hose colapsed, maybe you ate up an impeller.(maybe I did too again)-thus creating a problem that would mask the REAL problem.

[GEOO]

I took out the thermostat, and bypass. Engine runs cold now!!! That better then hot.
She only warmed up to 100 degree's, oil 140 to 200. Hum, I think I need a smaller restricter or a new thermostat with three large holes drilled in it. I must of been trapping air in the engine causing hot spots?? Thanks Guys, GEOO ;)

[mattyboy]

geoo,
glad to hear you got this one licked!
was taking out the bypass a big project?


Matt

[ALLAN BROWN]

GEOO, How the hell can you run fresh water cooling without a circulating pump? Please enlighten me. This could be a breakthrough!

AB

[GEOO]

Brownie, I switched to raw water cooling. Could not get my Fresh Water cooling system to work. GEOO :confused:

[BigGrizzly]

Geoo, Brownie sells the t-stat with three 3/16 holes in them. I made my own from a Robert shaw. This could have been your problem with the closed system. I don't know for sure, since all my closed systems have the holes and no bypass. It takes longr to warm up but it doesn't trap air.


Randy