SN200 2014 Overheating after shutdown and restart

[BertClijsters]

Hello,

I have the following problem with my Nautique 200 with PCM Excalibur 343 engine, when I shut off the engine for 10 to 20 minutes. Then I restart engine and let him run at idle, the engine suddenly starts overheating, when I burst some trothle the engine cools back to normal and stays there.
I allready changed impeller, changed thermostat, water strainer, thightned all clamps, looked for debrise in the oil cooler. I don't think it is an air leak.
My last options is to replace the circulation pump ????

When skiing temperature never rises 165 degree.

Somebody seen this issue before ???

[Rednucleus]

On re-start, how hot does it get and how quick after starting??

[BertClijsters]

When I restart engine and Idle on the lake for 2 tot 5 minutes, suddenly it starts rising fast it goes to 190 degree, but I always pop some throttle before it goes that high.
But once you rev the engine everything is normal and it doesn't overheat anymore at idle.
But I like to have it solved because I am not always at the helm of the boat.
When pulling skiers it goes to 165 degree, and when I drop of the skier it rises shortly to 170 - 172 and goes back to 160 after 10-20 sec.

[NautiqueJeff]

It is likely just the residual hot water that is in the engine getting purged. 190 wouldn't damage anything anyway. Let it run for a minute or so without giving it any throttle. I bet it will rise a bit and then cool right down.

[BertClijsters]

When I don't give any throttle it keeps on rising very fast. When idleing this happens after a few minutes not imedialty after restart. Suddenly it starts rising from 165 to 195+.
Could there be some air bubble in the system after restart ?
I checked all clamps from inlet to raw waterpump they are al really tight. Impeller is new, water strainer is new, I even changed serpentine belt and pulley tensioner.

[SkiToday]

Is there a chance you are idleing in shallow/weedy water? We had something similar happen in the past where weeds were blocking the intake opening on the bottom of the boat causing temp to rise fast but never entering the lines (at least I think that's what was going on). Then when you move, you dislodge those weeds?

[jpwhit]

Have you changed the thermostat? It may be sticking.

If not that, I would suspect an air leak on the suction side of the raw water pump. Best way to be absolutely sure you're not getting air into the system, is to install a few inches of hard clear pipe right at the intake of the raw water pump. If you see anything more than very small bubbles you have an air leak somewhere before that. I have a plastic tube with a few inches of rubber hose and some clamps in my boat tools for this purpose.

I can't see how the circulating pump could cause the symptoms you describe.

[BertClijsters]

Hello,

Yes thermostat is brand new, I don't think this is the problem.
Today I noticed after restart I waited 5 min and then put the boat in gear, then temp start rising very fast. I hear air bubbles in the hose that goes form the Y-junction top engine thermostat housing to the manifolds.

Can my dripless water cooled shaft seal cause the problem draining all the water from impeller and causing air lock ?

I replaced my water strainer, so he is brand new. See no bubbles at all in it.

Maybe it is the trans cooler that has an air leak on the drain plugs ? I am really sure that all clamps and hoses are tight and not leaking.

[bturner]

We had a MC that had a similar problem. The issue was from the strainer not sealing well. It would lose prime then form an air pocket in the line that the pump under idle could not overcome. It did the same thing if the boat was on a lift. When you put it in the water for the first start, if you didn't rev the engine a couple times no water would pull from the lake to cool the engine. MC had a service bulletin to replace the "defective" strainer with one of a different design and shorten the hose to the hull fitting. This fixed the restart issue but never really fixed the first start off the lift issue. On that I was looking at the belt driven raw water pump they went to that year which was replaced for the following year model. Not only was the location of the pump horrible, the impeller on the pump was a third of the width of the typical impeller you see inboards.

On yours I think jpwhit has a great idea with the clear hose to see if you're losing prime and creating an air pocket. If that's the case it's time to start checking all the hose connections and fittings. If you have a strainer with a clear lid or bowl, look for air bubbles and check any "O" rings. I like to use plumber's grease on the threads for the bowl and liberally use it on the "O" rings to ensure a good seal. I'm also assuming you've hit all the typical items like changing the raw water impeller and the thermostat. If it's started doing this recently, something has changed.

[BertClijsters]

Have you changed the thermostat? It may be sticking.

If not that, I would suspect an air leak on the suction side of the raw water pump. Best way to be absolutely sure you're not getting air into the system, is to install a few inches of hard clear pipe right at the intake of the raw water pump. If you see anything more than very small bubbles you have an air leak somewhere before that. I have a plastic tube with a few inches of plastic hose and some clamps in my boat tools for this purpose.

I can't see how the circulating pump could cause the symptoms you describe.

Is it normal that when I shut down my engine, all the water drains from the engine, I mean all water on de pressure side of the raw water pump ?

[jpwhit]

A good bit of the water on the engine circulating side will drain once the engine isn't running. Not all, but a lot of the water higher up normally drains. This is especially true if you have a water cooled dripless shaft seal since that provides a path for water to exit that is below the engine. Without that, the water will drain to the level where water exist through the exhaust manifolds.

[BertClijsters]

A good bit of the water on the engine circulating side will drain once the engine isn't running. Not all, but a lot of the water higher up normally drains. This is especially true if you have a water cooled dripless shaft seal since that provides a path for water to exit that is below the engine. Without that, the water will drain to the level where water exist through the exhaust manifolds.

Is it possible that the circulation pump has not ennough power to push the water through the engine at idle or cann’t overcome the air bubble that is created by the engine drain after the engine was shut off.
Maybe I must remove the transmission cooler and have a look for Some hair cracks.

[jpwhit]

That would be pretty rare. Most circulating pump issues happen at higher RPM. And having a boat run hot at idle and cool with a burst of throttle is such the classic symptom of an air leak on the suction side of the raw water pump. At idle, the raw water pump doesn't move a lot of water. So even the tiniest bit of air entering displaces more of the cooling water. When you rev the engine, the percentage of water to air goes up significantly just because the raw water pump starts moving a lot of water.

In my opinion, your time is better spent on being absolutely sure you have an adequate supply of water coming in from the raw water pump as the first step. Just because statistically, that's the problem 9 times out of 10. Can be caused by blockages, bad impeller, air leaks on the suction side. The reason even a tiny air leak will greatly reduce cooling water intake, is because the suction side of the raw water pump is under a negative pressure. So even a very small amount of air entering will expand into very large bubbles in that negative pressure and displace a large percentage of the cooling water.

Another way to verify if the problem is on the raw water intake side is run the boat using a fake-a-lake. Because the water pressure from the hose will keep the pressure on the suction side of the raw water pump positive and eliminate the possibility of air entering. I hesitate to suggest this very often, because there can be so many problems with a fake-a-lake that I typically don't like using them. You have to make sure you have an ample supply of water feeding the fake a lake. Before starting the engine, a lot of water should be spraying out around where it presses against the hull. Even when running a little water spraying out is a good sign that the water supply is more than is needed by the engine. But that's typically fairly hard to achieve. If the problem doesn't occur on the fake-a-lake, then it's likely the issue is the supply of input water. When running on the fake-a-lake, if you see even a tiny drip of water anywhere on the suction side of the raw water pump hoses and cooler, that's the source of your air leak. But even with a leak, it's not uncommon for it not to let leak water out when it's under pressure from the fake-a-lake.

Once you're absolutely sure there's not an issue with water intake volume, then I'd move on to other causes if the problem remains.

[BertClijsters]

That would be pretty rare. Most circulating pump issues happen at higher RPM. And having a boat run hot at idle and cool with a burst of throttle is such the classic symptom of an air leak on the suction side of the raw water pump. At idle, the raw water pump doesn't move a lot of water. So even the tiniest bit of air entering displaces more of the cooling water. When you rev the engine, the percentage of water to air goes up significantly just because the raw water pump starts moving a lot of water.

In my opinion, your time is better spent on being absolutely sure you have an adequate supply of water coming in from the raw water pump as the first step. Just because statistically, that's the problem 9 times out of 10. Can be caused by blockages, bad impeller, air leaks on the suction side. The reason even a tiny air leak will greatly reduce cooling water intake, is because the suction side of the raw water pump is under a negative pressure. So even a very small amount of air entering will expand into very large bubbles in that negative pressure and displace a large percentage of the cooling water.

Another way to verify if the problem is on the raw water intake side is run the boat using a fake-a-lake. Because the water pressure from the hose will keep the pressure on the suction side of the raw water pump positive and eliminate the possibility of air entering. I hesitate to suggest this very often, because there can be so many problems with a fake-a-lake that I typically don't like using them. You have to make sure you have an ample supply of water feeding the fake a lake. Before starting the engine, a lot of water should be spraying out around where it presses against the hull. Even when running a little water spraying out is a good sign that the water supply is more than is needed by the engine. But that's typically fairly hard to achieve. If the problem doesn't occur on the fake-a-lake, then it's likely the issue is the supply of input water. When running on the fake-a-lake, if you see even a tiny drip of water anywhere on the suction side of the raw water pump hoses and cooler, that's the source of your air leak. But even with a leak, it's not uncommon for it not to let leak water out when it's under pressure from the fake-a-lake.

Once you're absolutely sure there's not an issue with water intake volume, then I'd move on to other causes if the problem remains.

Ok, I understand your theory, but How can you explain that one burst of throttle solves the issue. It isnt overheating anymore at idle until you shut off the engine.
after restart, the overheating starts again.

[pauldixon]

I had a similar issue on a MC. Mine wouldn't prime after I put it in the water. I had to move quickly and get it going forwards at 5mph before it would prime and everything would be good. Turned out to be crud in the exhaust manifolds that was blocking the water getting out making it so the pump wouldn't prime. Higher speeds, RPM, fixed it. Ended up flushing the engine with acid to clean it out. With your boat I would expect to see exhaust manifold alarms though (EMWT)...