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Engine Merc 888 (Ford 302) getting hot after warming up

L

LakeErieFishing

Member
My engine is intermittently overheating. Engine temp stays cool then all at once spikes up. Impeller in outdrive is new. Using 143 degree thermostat. I've been advised I could have vapor lock - I'm going to drill a1/8" hole in the thermostat flange to see if that helps. I not, I'm thinking it's the water pump on the front of the engine ma be the issue It's not leaking but I wonder if water is circulating. Thoughts?
 
Maybe pump is cavitating,creating air bubbles in cooling system,thus overheating,insufficient water flow supply to pump. Is this issue happening at different rpms? Only at high,low, idle rpms. Try a compression test it doesn't cost anything!
 
Sounds like something is floating in the thermostat housing and causing the thermostat to hang up. I have seen this!!

Vapor lock is related to Gas fuel systems.

What they may have meant is steam pockets........

Based on the year of this I would rule that out.

Who did the outdrive impeller replacement?

What does the water hose between the gimbal housing and transom look like? Feel like? Kinked? Very hard?

When the impeller was replaced did the large soft square o-ring get put on top of water pump housing? this keeps exhaust gases from getting sucked into water stream at impeller housing
 
Johnny, it happens intermittently. New impeller in seawater pickup installed and it ran cool on the hose at low and higher rpm. The temp spikes up somewhat randomly. Vapor lock could be an issue. I'm pulling the thermostat to see if it runs cool without it. If if does ill drill a 1/8" hole in the thermostat flange and reinstall. Compression test in the water line?
 
Seawater impeller was correctly installed. I have not checked the hose between gimbal housing and transom. Where is that located and is it and easy job to replace?
 
at out drive there are three bellows and one water hose.
U joint bellows, exhaust bellows and short shift cable bellows

And WATER hose.

Yes it is a B!tch to replace!
 
The bellows or shift cable have nothing to do with any of your issues....................................................it was for description of area to look

My point is,

IF YOU LOOK, you will see the hose on the passenger side of gimbal assembly/outdrive.

If it is pinching when drive is down or is in bad shape it could be leaking.

You are running a over 30 year old set up..........
 
I have some questions

How do you know the impeller was installed correctly

You seem to know that so many things are good or not defective or contributing to your problems

BUT yet you have problems.............How do you know these things?

Maybe let us know what makes you sure all is so good but still problems exist?

Who ever told you to drill a hole is wrong
You have an issue (s) and the root cause (s) needs to be found.
 
kghost said:
I have some questions

How do you know the impeller was installed correctly

You seem to know that so many things are good or not defective or contributing to your problems

BUT yet you have problems.............How do you know these things?

Maybe let us know what makes you sure all is so good but still problems exist?

Who ever told you to drill a hole is wrong
You have an issue (s) and the root cause (s) needs to be found.
Click to expand...


Don't now for certain if the impeller was properly installed. What I can observe is this - with muffs on, with good water pressure and volume from a well, at low RPM a lot of water squirts out the sides of the muffs. Water is circulating and also coming out the exhaust and prop hub. Power up the engine to 1,500 and higher and all hose water gets sucked into the drive, and a lot more water comes out the exhaust and prop hub.

Coil is new this summer. Mechanical fuel pump is new. Electronic ignition module is new. Carb was rebuilt but that doesn’t mean itwas rebuilt right.
There is a rubber fuel hose from the tank to the fuelfilter. It’s 14 years old. It still feels very hard/solid but maybe it’sdisintegrated on the inside and is collapsing under high fuel draw. All other fuel lines are stainless and ingood shape, no kinks, etc.

 
kghost said:
I have some questions

How do you know the impeller was installed correctly

You seem to know that so many things are good or not defective or contributing to your problems

BUT yet you have problems.............How do you know these things?

Maybe let us know what makes you sure all is so good but still problems exist?

Who ever told you to drill a hole is wrong
You have an issue (s) and the root cause (s) needs to be found.
Click to expand...


What's the best way to check if water is circulating thru the manifolds and risers?
 
First off, on engine water pumps rarely fail...............Rarely. Not saying they don't but most times a seal will leak before you loose any water circulation.

You have three issues to look at with temp issues.

1. Water in, is it full and clean (little to no air bubbles)

2. water out, are there any water passages blocked or partially blocked due to rust etc.

3. sender or gauge is defective.


So if you were to remove the incoming water hose from the thermostat housing and attach a clear hose in its place you could see if the water is clear and without any bubbles. (remember bubbles in incoming water will create steam pockets in motor due to lack of constant water flow) Typically motor will get hot as RPMS increase. Sometimes this is the only way to tell. This is why I am asking about water pump impeller install and gimbal water hose. Sources of air bubbles!!

Water out as suggested use a infrared temp gun and get some readings, left to right may have some variation of 10-20 degrees but should not be too hot.
Measure in several locations and record where and what readings. If manifolds and elbows are good there is not much else to look for. There are little to no restriction in the exhaust path after the elbows to cause a lack of water getting out.

It is not uncommon for a sending unit to loose its ground path the the threaded portion giving a false reading to the gauge. So a light tightening of sender sometime re establishes the ground. No rtv or thread sealant on senders threads. it must be grounded.

Gauges can stick, they can read wrong and the only way to be certain is to replace it or use a known good one and try it.

If you are running the old style square LOG manifolds and elbows you are fighting a old and marginally good system.

The new center design which has been used now is 100% more effective than the old square log design
 
kghost said:
First off, on engine water pumps rarely fail...............Rarely. Not saying they don't but most times a seal will leak before you loose any water circulation.

You have three issues to look at with temp issues.

1. Water in, is it full and clean (little to no air bubbles)

2. water out, are there any water passages blocked or partially blocked due to rust etc.

3. sender or gauge is defective.


So if you were to remove the incoming water hose from the thermostat housing and attach a clear hose in its place you could see if the water is clear and without any bubbles. (remember bubbles in incoming water will create steam pockets in motor due to lack of constant water flow) Typically motor will get hot as RPMS increase. Sometimes this is the only way to tell. This is why I am asking about water pump impeller install and gimbal water hose. Sources of air bubbles!!

Water out as suggested use a infrared temp gun and get some readings, left to right may have some variation of 10-20 degrees but should not be too hot.
Measure in several locations and record where and what readings. If manifolds and elbows are good there is not much else to look for. There are little to no restriction in the exhaust path after the elbows to cause a lack of water getting out.

It is not uncommon for a sending unit to loose its ground path the the threaded portion giving a false reading to the gauge. So a light tightening of sender sometime re establishes the ground. No rtv or thread sealant on senders threads. it must be grounded.

Gauges can stick, they can read wrong and the only way to be certain is to replace it or use a known good one and try it.

If you are running the old style square LOG manifolds and elbows you are fighting a old and marginally good system.

The new center design which has been used now is 100% more effective than the old square log design
Click to expand...


Thanks or the suggestions and thoughts. The setup I have is the square logs manifolds. For the clear hose suggestion, where would I connect the hose and what diameter hose should I use?
 
same diameter as what is there. follow it from thermostat housing past power steering cooler to transom. measure and go to home depot and get cheap vinyl tubing.


Also are you sure you have the hoses going to the manifolds and elbows in the correct locations?

Have you looked at the thermostat housing and all the fittings where the hoses connect to see if there are any obstructions/rust growth etc.????

All I am suggesting to this point is typically for over temp issues..............we dont really know that you actually have any..........


You say it stays at temp ~ 150* but spikes from time to time but always returns..correct?

This may not be an issue at all so I would do as previously suggested and measure temps before and when this occurs and compare.......

This may not be a cooling problem at all but we dont know this yet.
 
kghost said:
same diameter as what is there. follow it from thermostat housing past power steering cooler to transom. measure and go to home depot and get cheap vinyl tubing.


Also are you sure you have the hoses going to the manifolds and elbows in the correct locations?

Have you looked at the thermostat housing and all the fittings where the hoses connect to see if there are any obstructions/rust growth etc.????

All I am suggesting to this point is typically for over temp issues..............we dont really know that you actually have any..........


You say it stays at temp ~ 150* but spikes from time to time but always returns..correct?

This may not be an issue at all so I would do as previously suggested and measure temps before and when this occurs and compare.......

This may not be a cooling problem at all but we dont know this yet.
Click to expand...

All hoses are connected to the correct locations, no leaks. I will pull them off to visually check for corrosion, obstructions and scaling. I am going to pull the thermostat and run the engine to see what happens before doing anything else. Then, if still hot, I'll make sure that good strong water flow is coming thru the hose to the thermostat/pump area. If flow is good I'll pull hoses and look for obstructions etc. I'll keep you posted.

Also, where is the water temp sensor on this engine, near the thermostat? Thanks much

"I'm not afraid to make mistakes, I'm not afraid to fix my mistakes either"
 
If you run engine without thermostat she will most likely overheat at higher rpms. There will be no back pressure in cooling system,thus causing aeration of coolant"air bubbles",And air doesn't cool well in liquid cooled engines! Sensor might be on the intake manifold,one wire going to it.
 
kghost said:
same diameter as what is there. follow it from thermostat housing past power steering cooler to transom. measure and go to home depot and get cheap vinyl tubing.


Also are you sure you have the hoses going to the manifolds and elbows in the correct locations?

Have you looked at the thermostat housing and all the fittings where the hoses connect to see if there are any obstructions/rust growth etc.????

All I am suggesting to this point is typically for over temp issues..............we dont really know that you actually have any..........


You say it stays at temp ~ 150* but spikes from time to time but always returns..correct?

This may not be an issue at all so I would do as previously suggested and measure temps before and when this occurs and compare.......

This may not be a cooling problem at all but we dont know this yet.
Click to expand...


Can you advise where the water temp sensor is on this engine? It's not on the thermostat.
 
Sending unit wire color is GREEN, should be near thermostat, into side of housing or in intake manifold where water passes thru.

Two schematic included.
 
kghost said:
Sending unit wire color is GREEN, should be near thermostat, into side of housing or in intake manifold where water passes thru.

Two schematic included.
Click to expand...

Okay - I'm trying to follow how the water circulating in the risers and exhaust manifold work. At what point does the cooling water get mixed with the exhaust gases? I can't tell if it's from the hose that enters the back or front of the manifolds. Or is it elsewhere??
 
kghost said:
First off, on engine water pumps rarely fail...............Rarely. Not saying they don't but most times a seal will leak before you loose any water circulation.

You have three issues to look at with temp issues.

1. Water in, is it full and clean (little to no air bubbles)

2. water out, are there any water passages blocked or partially blocked due to rust etc.

3. sender or gauge is defective.


So if you were to remove the incoming water hose from the thermostat housing and attach a clear hose in its place you could see if the water is clear and without any bubbles. (remember bubbles in incoming water will create steam pockets in motor due to lack of constant water flow) Typically motor will get hot as RPMS increase. Sometimes this is the only way to tell. This is why I am asking about water pump impeller install and gimbal water hose. Sources of air bubbles!!

Water out as suggested use a infrared temp gun and get some readings, left to right may have some variation of 10-20 degrees but should not be too hot.
Measure in several locations and record where and what readings. If manifolds and elbows are good there is not much else to look for. There are little to no restriction in the exhaust path after the elbows to cause a lack of water getting out.

It is not uncommon for a sending unit to loose its ground path the the threaded portion giving a false reading to the gauge. So a light tightening of sender sometime re establishes the ground. No rtv or thread sealant on senders threads. it must be grounded.

Gauges can stick, they can read wrong and the only way to be certain is to replace it or use a known good one and try it.

If you are running the old style square LOG manifolds and elbows you are fighting a old and marginally good system.

The new center design which has been used now is 100% more effective than the old square log design
Click to expand...

I'm in the process of draining the engine block, risers and manifolds and backfilling all those with Evapo-rust. This product eats rust, and I mean surface rust, chips, flakes, and chunks (any and all blockage) without damaging the metal or hoses. Put it in, leave it overnight, then drain and reuse.
 
kghost said:
Sounds like something is floating in the thermostat housing and causing the thermostat to hang up. I have seen this!!

Vapor lock is related to Gas fuel systems.

What they may have meant is steam pockets........

Based on the year of this I would rule that out.

Who did the outdrive impeller replacement?

What does the water hose between the gimbal housing and transom look like? Feel like? Kinked? Very hard?

When the impeller was replaced did the large soft square o-ring get put on top of water pump housing? this keeps exhaust gases from getting sucked into water stream at impeller housing
Click to expand...


What about the water pocket cover? I haven't checked it yet. If I need to replace it what do you suggest? Wondering if I'd need to heat the bolts.
 
While Jack and I seldom agree, post #3 offers you some good info. Take heed!

LakeErieFishing said:
What's the best way to check if water is circulating thru the manifolds and risers?
Click to expand...

If your system is like the one shown in post #22, your exhaust system does not include "risers/spacers".
The 888 has log style manifolds and rear elbows. (I've owned and have worked on these over the years)

In either event, warm the engine up and crack all exhaust component bolts loose.
When things cool back down, remove all exhaust components.

Check the seawater transfer ports between manifolds and elbows.
These must all be clean and free-flowing.

You enquired about the area where the seawater enters the exhaust flow. That would be the "mixing" chamber.
Yes..... very important that these ports are clear and free-flowing as well.

All of this can be examined with the exhaust system removed.


The belt driven pump at the front of the Ford Engine is the "engine circulating pump".
For a Closed Cooling system engine, the Automotive circ pump works just fine.
However, and again if your system is RWC (like the image shows in post #22,) the circ pump's metallic impeller must be made of bronze or SS in order to hold up in that environment.

If the metallic impeller was not the correct material for Raw Water use, it may be bad by now.
I would suggest that you pull it and examine it.


LakeErieFishing said:
Okay - I'm trying to follow how the water circulating in the risers and exhaust manifold work. At what point does the cooling water get mixed with the exhaust gases? Ican't tell if it's from the hose that enters the back or front of the manifolds. Or is it elsewhere??
Click to expand...

Yes, this occurs elsewhere within the exhaust Elbows.


**************************************

In my opinion, the OEM 888 exhaust cooling system is more complex than need be. The routing of hoses from T-stat housing...... In/Out of manifolds..... back to T-stat housing.... then on to Elbows...... etc.

If you were to replace the exhaust manifolds/elbows, you can simplify the system by using a "center-rise" manifold and elbow, and going with a more conventional T-stat housing.
You would supply cooling water to the manifolds only, allowing the transfer ports to direct it up and out.

Just a thought!




.


.

 
Last edited:
RicardoMarine said:
While Jack and I seldom agree, post #3 offers you some good info. Take heed!


If OEM, your exhaust system does not include "risers/spacers"...... the 888 has log style manifolds and rear elbows.
(I've owned and have worked on many of these)

In either event, warm the engine up and crack all exhaust component bolts loose.
When things cool back down, remove all exhaust components.

Check the seawater transfer ports between manifolds and elbows.
These must all be clean and free-flowing.

You enquired about the area where the seawater enters the exhaust flow. That would be the "mixing" chamber.
Yes..... very important that these ports are clear and free-flowing as well.

All of this can be examined with the exhaust system removed.


The belt driven pump at the front of the Ford Engine is the "engine circulating pump".
For a Closed Cooling system engine, the Automotive circ pump works just fine.
However, for Raw Water cooled engines, the metallic impeller must be made of bronze or SS in order to hold up in that invironment.

If the metallic impeller was not the correct material for Raw Water use, it may be bad.
I would suggest that you pull it and examine it.




Yes, this occurs elsewhere within the exhaust Elbows.


In my opinion, the OEM 888 exhaust cooling system is more complex than need be.
If you were to replace the exhaust manifolds/elbows, you can simplify the system by using a "center-rise" manifold and elbow, and going with a more conventional T-stat housing.
You would supply cooling water to the manifolds only, allowing the transfer ports to direct it up

Click to expand...


What about the water pocket cover? I haven't checked it yet. If it has gotten hot and is warped or the gasket has been damaged, or the tube damaged, that could prevent good water flow from reaching the engine.

I will be checking the risers and logs. Also the water circulating pump
 
Many over-heating issues can be traced back to:

Seawater pump impeller failure.
Coolant supply hose interior delamination (rare).
The Gimbal Housing's S hose that Jack referenced.
Engine Circ pump being incorrect for RWC'd engine.
Rust Scale blocking exhaust component transfer ports and mixing chamber ports.
Rust Scale within the T-stat housing ports.


We bolt these parts on, and we seldom remove them for routine or periodic inspection.
Add years of useage...... and you can imagine what can occur inside of them!!!!!


By the way...... a Marine thermostat should come with a small air bleed hole already existing.
 
RicardoMarine said:
Many over-heating issues can be traced back to:

Seawater pump impeller failure.
Coolant supply hose interior delamination (rare).
The Gimbal Housing's S hose that Jack referenced.
Engine Circ pump being incorrect for RWC'd engine.
Rust Scale blocking exhaust component transfer ports and mixing chamber ports.
Rust Scale within the T-stat housing ports.


We bolt these parts on, and we seldom remove them for routine or periodic inspection.
Add years of useage...... and you can imagine what can occur inside of them!!!!!


By the way...... a Marine thermostat should come with a small air bleed hole already existing.
Click to expand...

Excellent information - thank you! I will be inspecting all of these elements later next week. I'll keep all posted.
 
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