1986 Bayliner Capri AQ131/275 Over heating

[stratostan]

My 1986 Bayliner Capri AQ131/275 Over heating is still running hot after having the thermostat replaced, rinsing out the radiator and fresh water lines and replacing the impeller. What else can I try? Does the temperature of the inboard engine compartment impact the overheating? I had added carpet to the center console to redo the interior of the boat. I am wondering if that is my issue or what else I can check?

 

[cptbill]

could it be that the gage is showing a high temp that's not really high like a bad gage or water temp sending unit?

 

[stratostan]

The gauge does read hot, but it ends up overheating and steam rolls out of the engine.

 

[Bondo]

Ayuh,.... Welcome Aboard,.... Look for a vacuum leak, 'tween the raw water pump, 'n the water yer boatin' in,....

 

[Fishermark]

To follow up on Bondo's point - a common problem is the metal connector on the outdrive where the hose connects. It often corrodes and causes the vacuum leak.

 

[Fishermark]

Here's a pic from the archives (from capt mello?) showing the part I am referring to:

 

[mopower440]

Here's a pic from the archives (from capt mello?) showing the part I am referring to:

That was a problem with mine, that water neck was rotted out like your pic..

 

[dennis461]

Start with simple troubleshooting.
I'll assume the impeller is actually spinning with engine running
1. open the lid on the strainer with boat in water, engine OFF.
2. note height of water
3. start engine
If water overflows, stop engine.
If water does not come up, your problem is raw water intake., air leak, pump housing worn, tubes fitting in the leg

If water overflows, stop engine put cover back on.

4. open petcock under the exhaust manifold
5. start engine.
6 if water flows out, your heat exchanger is probably OK.
7 If no water comes out,
8 stop engine
open drain on the copper tube under the exhaust manifold.
start engine
9 if water comes out now but not in step 6, you may have a clogged exh. manifold.

 

[dennis461]

That was a problem with mine, that water neck was rotted out like your pic..

The OP did not post a picture.

 

[stratostan]

Water is making through the system. Is it possible to bypass the radiator all together and just use the raw water to cool the motor? Would I need to eliminate my thermostat?

 

[dennis461]

Water is making through the system. Is it possible to bypass the radiator all together and just use the raw water to cool the motor? Would I need to eliminate my thermostat?

I'd say in your case that would not work. Why? because you have not found the cause. If you have a blown head gasket putting exhaust into the water jacket, it will still overheat. If the coolant pump (jacket water) is corroded and not pumping enough water, you will still overheat.

You say water is making it through the system, but you need lot of water.
Did you do the troubleshooting I posted?

 

[stratostan]

I did the trouble shooting. I am getting a steady spray of water out of the exhaust manifold petcock. I did a radiator flush to help clean the system. What material is the radiator made out of? I have a small leak near one of the holes for the boat I need to have repaired.

 

[dennis461]

If you have the original heat exchanger, the outer body is aluminum, inside is a rectangular copper thing with tubes and fins which allow heat to transfer.
You may need to open it up and see if the fins are clogged with seaweed. There is also a rubber like device inside which directs the water through the fins. I can't seem to find my pictures.

If fins are clogged and water by-passing the fins, you will overheat.
Does it overheat at idle?

You also need to figure out if the 'other' pump is working. Which is hard to do.

 

[jerryjerry05]

There are 3 things that might be a problem.
​The manifold can look NEW and be BAD!!
You have to take it off and inspect the end for blockage. Do a flow test.

Went on an overheat job.
The same setup as this one.
The manifold, I could actually push in the side.
The paint was the only thing holding it together.

The heat exchanger insert, it gets clogged and stops the flow of cooled water.
Sometimes a flush works, sometimes a boil out at a radiator shop works,sometimes an acid dip works.
Take it to a shop, don't try the acid yourself.

This part is CRAZY expensive.$1000+
Maybe e-bay for a used part "​855453 Volvo marine heat exchanger" $160

The water pump: the impeller, or the cam wear plate wears down and not enough water is pumped into the motor.

My first guess is the manifold.

 

[stratostan]

That was a problem with mine, that water neck was rotted out like your pic..

Where is this part located? Is it back against the inside wall on the left side of the boat when you are facing the engine compartment from the boat? The tube on my boat, looks different than this if it is. It still has the same diamond shaped flange but is longer and curves back towards the hose that runs to the fresh water filter tube. I could not get it loose last night? is it fastened from the outside somehow? I just wanted to say thank you to everyone who has posted on my issue so far! Great information.

 

[dennis461]

No Title

Where is this part located? Is it back against the inside wall on the left side of the boat when you are facing the engine compartment from the boat? The tube on my boat, looks different than this if it is. It still has the same diamond shaped flange but is longer and curves back towards the hose that runs to the fresh water filter tube. I could not get it loose last night? is it fastened from the outside somehow? I just wanted to say thank you to everyone who has posted on my issue so far! Great information.

The part is on the OUTSIDE of the boat.
If you run fine OFF-PLANE but overheat ON-PLANE, then you look for the 'leg' parts to be a problem.
If you have plenty of water flow with the leg in a water drum, then it is not your problem.
Notice in the picture, the inlet elbow is in the air, not water.
If the rubber hose is loose allowing air in, no water can flow from the bucket .
Most boats, the elbow is in the air when ON-PLANE, submerged at the dock.

 

[stratostan]

Any advice on replacing this part? I have one on order, just wondering if there is a best practice method to replacing?

 

[stratostan]

Is it hard to get this part out? It should be coming in the mail tonight.

 

[dennis461]

Is it hard to get this part out? It should be coming in the mail tonight.

It's a full six-pack job.
Mine is held onto the drive with allen head stainless steel cap screws, Easy to remove.
If yours has Philips head screws, you will find it almost impossible to get a screwdriver in there.
If they are corroded/stuck. You've got a big job ahead of you,

Next is the hose clamp.
When I replaced all my hoses, I put this one on first, then the exhaust and drive bellows.
So my hose clamp if facing wrong, cannot get a screwdriver on it to loosen{: 'It does have a hex slotted head hose clamp, so maybe a ratchet open-end wrench could get it loose.

You may have to remove the bellows and raise the transmission.

Does you engine run fine in a bucket like my picture shows?
I it over heats on plane, I have an alternate cooling method to share with you to help finish the season.

 

[stratostan]

It runs great when on the lift submerged, but it does start to overheat when I get on plane. What is your alternative method?