Boat won't start when it's hot

electricaldoctor said:
Take the thermostat out and put it in boiling hot water. You should see it operate if it is any good. The thermostat should have the temperature rating on it. Check to see if it is the correct temperature rating for your engine. Replace the thermostat correctlly with a good gasget.
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Do you guys have any resources on how to properly change the thermostat? I don't want to mess this up.
 
muskokamarc said:
I called my local marina and they suggested that it could be something called a 'hot soak'. They said it is possible that the carb is getting flooded with fuel and that's what could be causing it to not start back up after it's warm. Any thoughts?
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I’ve seen it on cars.

When you shut down, the heat boils the fuel in the carburetor and it either spills out and into the intake manifold or evaporates.

You could try a phenolic spacer under the carburetor to insulate it from the heat of the intake manifold.

Phenolic is a plastic like material, maybe 1/2”-1” thick and cut out for the specific carburetor that you have.
 
Espos4 said:
I’ve seen it on cars.

When you shut down, the heat boils the fuel in the carburetor and it either spills out and into the intake manifold or evaporates.

You could try a phenolic spacer under the carburetor to insulate it from the heat of the intake manifold.

Phenolic is a plastic like material, maybe 1/2”-1” thick and cut out for the specific carburetor that you have.
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That sounds a lot cheaper than the carb rebuilding they suggested I might need... Would a carb rebuild even fix this issue though?
 
Probably not. If the heat is the issue, you need to do something to keep the fuel cool after shutting down.

opening the engine cover, installing the spacer, etc.

I discovered this on my car and saw it myself when I removed the air cleaner and I could see fuel dripping into the intake manifold right after shutting the engine off

I installed a 1/2” phenolic spacer under the carburetor (Carter AVS) and that stopped the problem.
 
Espos4 said:
Probably not. If the heat is the issue, you need to do something to keep the fuel cool after shutting down.

opening the engine cover, installing the spacer, etc.

I discovered this on my car and saw it myself when I removed the air cleaner and I could see fuel dripping into the intake manifold right after shutting the engine off

I installed a 1/2” phenolic spacer under the carburetor (Carter AVS) and that stopped the problem.
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So i suppose i need to find out why the engine is running hot in the first place and resolve that, which will likely fix this issue then... Going to start with thermostat.
 
muskokamarc said:
So i suppose i need to find out why the engine is running hot in the first place and resolve that, which will likely fix this issue then... Going to start with thermostat.
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I just went back and re-read this thread. I agree. You need to find the reason for the engine running hot.

if this was my boat, I’d remove those original risers for an inspection.
You could also remove the brass plugs from the underside of the exhaust manifolds to check for debris. They could be clogged and contributing to the overheating.

You should also check the volume of water that the raw water pump is putting out.
 
Espos4 said:
I just went back and re-read this thread. I agree. You need to find the reason for the engine running hot.

if this was my boat, I’d remove those original risers for an inspection.
You could also remove the brass plugs from the underside of the exhaust manifolds to check for debris. They could be clogged and contributing to the overheating.

You should also check the volume of water that the raw water pump is putting out.
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Might have them do this as it seems like a pretty big job to correct if there is something wrong.
 
Espos4 said:
I just went back and re-read this thread. I agree. You need to find the reason for the engine running hot.

if this was my boat, I’d remove those original risers for an inspection.
You could also remove the brass plugs from the underside of the exhaust manifolds to check for debris. They could be clogged and contributing to the overheating.

You should also check the volume of water that the raw water pump is putting out.
Click to expand...
Now that you mention it... When i went to pull those brass plugs to winterize the boat in November, I remember having to jab inside with a tooth pick of sorts, in order to get the water to flow out...
 
It's certainly possible. Here's a good description of Heat Soak on the edelbrock site https://www.edelblog.com/tech-tips/resolving-heat-soak essentially the fuel is getting hot and pressure builds up and forces open the needle valve in the carb, causing flooding. Or it's getting hot enough to vaporize the fuel which is vapor lock. Modern fuels have a lower vapor point than the stuff we bought back in the 70's and 80's. Have an engine mechanic look at it.
 
Espos4 said:
I just went back and re-read this thread. I agree. You need to find the reason for the engine running hot.

if this was my boat, I’d remove those original risers for an inspection.
You could also remove the brass plugs from the underside of the exhaust manifolds to check for debris. They could be clogged and contributing to the overheating.

You should also check the volume of water that the raw water pump is putting out.
Click to expand...
I started it up today and took my infrared thermometer and noted that the left exhaust manifold is at ~120 Fahrenheit when at idle and the right one is at ~95. Could it be a bad manifold?
 
Could be.
As a general rule, the risers should be only slightly warm. You should be able To keep your hands on top of the risers without feeling to hot.

The sides of the manifold generally get too hot to keep your hand on it for more than 1-2 seconds.
 
There is always rust and sand in brass plug when you winterize. Common to prob holes to get to flow correctly. Take your riser off fill it with water after you block off where water can come out. leave over night if water is down bad riser.
Good Luck
 
So I was chatting with the marina owner and he is suggested to remove the sterndrive and shoot compressed air through all the passages to clear any blockages. He believes the exhaust flappers may have rusted off and gotten stuck, restricting the flow of water.

He said that if the overheating is due to the manifolds corroding, it is going to be a very expensive fix ($8k canadian)...

He also recommended removing the thermostat from the boat altogether to have maximum cooling. We only use the boat from May - September so he doesn't think we would have any issues with cold weather starts.

What are your thoughts on the above?
 
You need the thermostat, dont remove it. Find out why its hot. have you ever serviced the raw water pump? Also the risers get hot all of mine do/ did and one side is always a little hotter for some reason? Go over your cooling system from the outdrive to the wye pipe look for worn or missing parts. Its common on these older boats.
 
Ottawamerc said:
You need the thermostat, dont remove it. Find out why its hot. have you ever serviced the raw water pump? Also the risers get hot all of mine do/ did and one side is always a little hotter for some reason? Go over your cooling system from the outdrive to the wye pipe look for worn or missing parts. Its common on these older boats.
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If you mean the impeller by raw water pump, then yes, it was done last summer by the same marina.

I am worried that it's corrosion in the manifolds... The boat only has 600 hours on in it but that's apparently not good as it means there could be a build up of corrosion since it is not used often.

He mentioned that people used to do an 'acid wash' on the engine. Does anyone ever do this anymore? He was not willing to do it given the harm it can cause to the environment.
 
The boat is currently at the marina and they were unable to get it to overheat... Of course these things never happen when you need them to...

They removed the thermostat as they think it will provide maximum cooling to the engine preventing it from getting too hot, which may be why it has a hard start after it gets warm.

I have heard that removing the thermostat will allow the cooling water to pass through the block too fast to absorb all the heat.

I guess I will take it back and see if I get stuck on the lake again or not. If i get stuck again where I'm on the lake and its turning over but wont start, he said to advance full throttle and try to start it. If it starts, then it is a flooded engine and likely a carb rebuild.
 
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I gave the go ahead for the carb rebuild as I am getting fed up with not being able to enjoy the boat.

I think the engine is getting flooded after longer drives which is why it wont restart when it's warm. Will be $325 CAD labour and ~$80-140 for the carb kit so we shall see if this resolves issue...
 
Ok so on another thread someone mentioned that their fuel line (yellowish clear one) was filled with fuel permanently due to a ruptured fuel diaphragm which was the reason they were having trouble with hot starts. I think that's the same issue with mine so I'm going to have the fuel pump replaced, and then im debating on whether or not to do the carb at the same time or just wait and see what happens.
 
Greetings

The hoses on the raw water pump can easily be installed backward (ie. intake on out port and vice versa). The back side of the pump has a cast in label for which goes where. How do I know this you ask........................................................................:eek:
 
Did you get this resolved?
You're probably out for the season at this stage in Ontario but,

It almost certainly could be vapor lock, but why is the question.
Carbs will boil off and empty after shutdown from heat, and the fuel pump can also vapor lock from excess block heat.
Excessive heat can also affect the thunderbolt ignition modules.
First solve any running hot problem, vapor lock could just be aggravated by the excessive heat.

If it still happens next spring
When it wont start, open the engine compartment and ventilate, take off the flame arrestor, and have someone pump the throttle once (not cranking the engine) while you watch. You should see gas squirt into the throat from the accelerator pump. If not or just a dribble, the bowl is empty, a sure sign of a vapor locked carb. - Reinstall the flame arrestor.
Try pouring some cold water over the mechanical fuel pump to cool it down. Then try restarting.
It may take a few cranks to refill the carb but if it starts this again confirms vapor lock.
 
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