454 Mag Overheating - Help!
 

One for the collective...

So I have my new to me Formula. '89 242 LS, 454 Mag, Bravo. Engine runs great with the exception of an overheat condition.

Here are the facts:

Engine idled a little warm at first but thought that it was typical "on the hose" warming up. It once got to about 190 on the hose (high idle) but I thought not much of it. Took the boat out, and within about two miles of running, the engine would creep up to 200. Not good. If I kept the engine running well under 3k rpm, it seemed to creep up very slowly. Going back to idling would keep the temp around 150. Found trash in the oil cooler from a bad impeller (new one installed... forgot to clean out the line). Still overheating. Water flow from the sea water pump is enough to flood the bilge quickly (at least at idle, though I tried this same test on the hose at home with higher speed and lost water output and it was pulsing... not enough water at the hose probably).

Got the boat back home, and found that the thermostat had some issues. Removed the thermostat, and ran on the hose. Ran it particularly hard on the hose (of course no load), and the engine wouldn't go above 130. Thought it was fixed (needed a new sleeve to install the thermostat... left it out to test). Took the boat out Father's Day. Again, same issue, though not as quick to overheat.

I went back to the boat the other day and pulled the manifolds. I thought they were good, but lots of scale flaking off on the exhaust side with some evidence of water intrusion. They have to be replaced. I also pulled the circulating pump and its inspection plate. The bearing is shot but the vains apear ok from what little I can see.

I need to get this figured out. I am using IMCO risers on the stock manifolds. The risers are ice cold running on the hose... manifolds hot.

Any ideas?

Thanks!
Tom

How many salt water hours on the boat total? Sounds to me that you have years of scaling built up blocking passages. check all ins and outs of block and manifold.

your risers are cold and mani hot because the thermo housing runs water straight through to the risers when thermo is closed.

also, you may want to get a mirror to the inlet side of the oil cooler. You just might have old impeller jammed into the cooling tubes enough to restrict flow

also the hose joint at the transom. that is where the hose is at it's smallest. junk can pile up at the fitting in transom. blow it out backwards. put hose on pump inlet hose and blast it out thru drive.

I will go through everything again in terms of hose routing between the transom and the thermostat housing. It's possible that there could be some material wedged into the oil cooler. I back flushed it, but something could still be in there. We'll see.

I noticed that there was a good amount of steam coming from the exhaust when trying to get on plane (before it was showing an overheat). And to me anyway, it seems that there just isn't the volume of water coming out of the exhaust that I would expect (boat has the silent thunder platform... and the plugs are installed).

Oh, and the boat was purchased in Florida, and then made it's way up to the Annapolis area. Lots of salt I'm assuming. The whole pakage has 485 hours on it.
Hoping to get this figured out quickly.

ok that changes things a bit. You need to def check the freshwater hose coming from the drive to the transom. I'm betting you cant get your pinky in it where it enters the transom. Not an easy project to do with the engine installed. remove the elbow inside the boat and see how small the passage is for water to come in.. I would still get an inspection mirror to the inlet of the oil cooler too..

A friend mentioned this to me already... I had the hose off and looked at that. My pinky goes in fine though I can't really get that far into it to really check the elbow. I know this is supposed to be a pretty big issue on early Bravo set ups. If there was a problem at the transom, would it pump enough water to basically flood the bilge in a matter of a minute?

I would check all areas u can on the block first. If you still have the recir pump off those two outlets are good places to check, dig in there with a screwdriver and see what u find. Also with the thermos housing off check the intake for blockage. Check the exhaust, and the outlets of the risers.

I know the intake looked good. But I am going to dig around some. I have some engine brushes too that I can use to get into the outlet from the transom.

Water slowly heating up definitely points to a blockage/flow issue IMO... agreed?

if the boat has seen allot of sandy areas the block could have sand in it. we see it in our area once in awhile and have to flush them out real good.

http://i1225.photobucket.com/albums/...ngmi/38659.png

Ok, the hose that goes from the bellhousing to the outer transom and then to part number 23 in this picture could be your problem. You have to remove #23 and have a look at the hose there.

If there is a sand issue it will also plug up some of the oil cooler viens. Check the oil cooler and if they are plugged with any sand it needs removed to get sand out.

Sorry to say could be a head gasket. If the engine is salt water cooled and not flushed with fresh water after every use, the small steel gasket between block and cylinder can corrode. A simple compression test will tell. At idle no load and water cold. While you're under way,the higher revs force more combustion into engine. can't really overheat as long as a constant flow of cold water moves thru the engine. I suspect gasket because you seem to have a good water flow. With a sealed fresh water system you would overheat. I have 35 years with Chevy and although a more common problem on a 350 small block(4" bore), it isn't impossible for the big block. Either way I would definitely check before storage. If water left in a cylinder for too long, it will seize engine. Sometimes it will eventually blow into the oil. Oil will overfill and look like coffee w/cream. Also if hard to start sometimes it is because water is getting into a cylinder.

Solved. Bad pump. Heads were changed 50 hours ago.

Thanks everyone!!

I can tell you to cure the problem no question, but you must make checks.
1) Take off the water supply hose to the thermostat and let it dangle into the bilge. (not on anything that it will hurt) Now remove the output hose that comes from the rubber impeller pump and put the city water hose into there and clamp. Turn on the hose full on and notice how much comes from the t/stat hose. If it flows full and no pressure occurs where the water comes in, your hoses of your engine are clear. If limited flow of t/stat hose or pressure where the hose comes in, you have a clogged oil cooler or defective hose with internal flap restricting your water.
2) Put the t/stat hose back on the housing and re pressure the hose, now you are checking the hoses plus your exhaust passages. Once under pressure of city hose should see plenty water from the prop and exhaust relief passages, and no pressure where the hose goes into the pump discharg hose because high pressure there will indicate the water cannot flow easily through the elbows. If the pressure shows up remove the elbows and either clear or replace them.
3) The water pump may be at at fault.
With the output hose of the pump disconnected , remove the input from the plastic adapter on the transom plate and place it in a large bucket. With out the city pressure of a flushette, the pump even just about idle speed should empty the bucket and the output of the pump should produce a large amount of water. If not check for the impeller or the condition of theend plates on the pump body if the pump is a solid brass pump.
4) Bravoitis could be the problem.
While the plastic adapter is off for the previous test, put your flushette on the drive and pressure it up.
Look at how much water comes out of the fwd end of the bell to t/p hose through the transom assembly
and if the water looks limited this may be the problem.
with a light inspect the tip of the hose just behind the plastic adapter and see if the hose and internal hollow plug has been crushed and limiting the flow to the pump.
One of the four sections is causing the problem. Check them one at a time.
good luck Buddy

Already figured it out... and found a bad transom in the process. The water passage coming through the drive was pinched **** by corrosion. I went to install a thru-transom pickup, and drilled into confetti. Ouch.

I'm redoing the transom and stringers this winter.

Thanks for the note!