2003 50 SX Overheating

"Ran lower unit into soft, fin

"Ran lower unit into soft, fine gravel bar. After getting off the bar, engine began to overheat. Took it out of the water and disconnected the raw water hose at the input side of the impeller and flushed out muddy sand. Did this with hose connected to the connection "T"ed into the same hose. "Stuff" also flushed out of the lower unit. Now back flushing clean water through power steering cooler and out the lower unit intakes. Replaced the impeller and seem to have clean water everywhere now. Also removed drains from the manifolds and ran water through these. With boat in water or with muffs installed I am getting clean water through the system. Boat would gt hot at any thing over 1500 rpm. Thermostat tested OK, but removed anyway and boat will run up to 3000 rpm constantly without overheating, but anything over and it gets hot 210-220+ and alarm goes off. Can cut back to under 3000 rpm and it cools of quick. Can I find this problem with a laser thermometer? Have checked and ran water through everything I can find. With muffs connected should a water hose connected to home faucet push enough water to come out of the impeller housing (with it off crank and impeller out)? I don't get any water. Partial blockage somewhere? WHERE!!? Thanks..."

"Is your engine raw water cool

"Is your engine raw water cooled? If so you may have gravel in the block cooling passages. You may try to flush the block with a mixture of water and compressed air, and if you see gravel/sand coming out then you know this is the problem, in which case may take a bit of patience to get rid of the obstruction."

"Also, you may want to disconn

"Also, you may want to disconnect the raw water hoses in the steeering oil cooler and visually check that the cooler tubes are not partially blocked. Backflushing with a garden hose will not be sufficient if you have enough water flow."

"Sorry, I will reword it: &#34

"Sorry, I will reword it: "Backflushing with a garden hose will not be sufficient to determine whether or not you have enough water flow""

I will try both of these today

I will try both of these today.

Hey El Pescador.

How much o

Hey El Pescador.

How much of this stuff would your raw water strainer (that you show in the other post) have caught? I would assume all correct? I just don't understand why all boats do not have these so that we don't have to go through what Kevin is going through right now. Although I have never had the same problem I can't see not putting one on my boat now.

"Chris, the size of the holes

"Chris, the size of the holes in the strainer I will be using is 1/32" while the size of the openings at the water intake grid on a 280 leg are 1/4" x 9/16". I would say that virtually all what passed through the leg grid would have been trapped by the strainer; and, as a general rule, whatever would have managed to pass through the strainer would be so small that it would not have done any harm to the cooling system.

Personally, I think that raw water strainers are cheap insurance against situations like the one Kevin has just experienced."

This is my first inboard and I

This is my first inboard and I figured there would be some sort of screen in the lower unit. Obviously there is not one. I have not worked on the boat today yet. I will post my findings.

"Ok guys. Engine block is flu

"Ok guys. Engine block is flushed. Power steering cooler is all clear. Impeller housing has no grooves in it. I disconnected the large hose that connects the exhaust to the outdrive and flushed. I did get a litlle bit of muddy water / very small amount of stuff from each exhaust manifold. I did this by connecting the hose to the drain on the rear of the manifold and flushing backwards. More out of one side than the other, but it still wasn't very much. When I connect the muffs to the out drive I have to hold them very tight against the intake holes to get any water at all up to the impeller pump. This is with the impeller housing off the crank and the impeller removed. Any chance something could be somewhere in the lower/upper unit? What about the large tubes that connect to the manifolds (bellows?), do they restrict down to any size that could cause enough restriction? I have not fired the engine and retested yet. Boat is at home. We have a well that flows a little more water than a public system. Is it a fair test to connect a hose to the hose by the engine and run the egine at 3k+ rpm. Will it get enough water to stay cool in a normal flowing situation? Thanks."

"To test the boat on the trail

"To test the boat on the trailer you should use a bucket or a container large enough to put under your outdrive and fill it with water until well-above the water intake grids. However, this way you will be running the engine at high RPM but without load. If it overheats with no load, then you have a serious lack of flow problem. To discard the possibility of gravel inside the outdrive causing the lack of flow, you can disconnect the hose between the outdrive and the transom shield and run a hose from the transom shield to the bucket. If the engine runs cool at higher RPM, then you know where the problem is.

The Y-pipe restricts at the bottom. To check for debris, just disconnect the exhaust bellows between the transom shield and the outdrive.

The other thing you can do is put the boat in the water, run it at high RPM under load (boat planing) and bring a laser thermometer to pinpoint which areas are hot."

"El Pescador, There is a hose

"El Pescador, There is a hose connection in the line between the power steering cooler and the impeller (raw water pump) if I simply connect the water hose to this input and run the engine at upper rpms, this will put fresh water to the impeller. So you are saying that I should be able to run the engine as much as I want and it not get hot if everything is working/flowing properly from that point forward? Basically this would eliminate the outdrive and it's intakes from the equation. If it still gets hot then there is something going on within the engine and the cooling system. Could anything besides the cooling system be wrong. Could it have gotten so hot that I did some serious damage? It runs smooth and starts fine. No visible smoke, water in the oil, or reduced performance."

Sorry I didn't update ever

Sorry I didn't update everyone on the solution of the 5.0 overheating. It was a blown head gasket on 30+ hour boat. Must have had a near complete blockage and ran it fairly dry of any water. Thanks for all the info!!