Riddle me this....Overheating issue with a twist

[Fodder]

Good day All.

I'm having some issues with A4 overheating that is making me scratch my head. Let me start by saying that Cahoots was struck by lightning last summer and has spent the winter in dry-dock getting repaired. Pretty much all of the electronics instruments were replaced, including a new 100amp Moyer alternator and a new Indigo EI system. So far, so good.

There were also new through-hulls and sea-cocks installed throughout the boat as they had all been spider-cracked.



The engine intake seacock has already started to rust as they used a galvanized collar instead of brass like the rest of the unit. The engine uses the hot-water by-pass setup that many people on this forum have with NO thermostat and has run well for years this way. I've taken the hoses going to the water-heater loop out of the equation for troubleshooting purposes. (It overheats with or without them attached)



What is causing me to scratch my head is the fact that if I pull the raw water intake hose off of the water filter and directly into a bucket, the engine runs perfectly and I am able to adjust the temperature up and down using the valve. I had the engine going for 20 mins under load (tied to the dock) and topped out at 140 degrees. However, when I re-connect either directly to the through-hull or the water filter, the engine will quickly start to overheat and steam no matter how much I close off the adjustment valve.

Here's what I've tried :

1. Suck and blow test (easy fellas) on the tube connected to the sea-cock. Seems okay.
2. Acid washed the engine. I had about a 33% solution left in for 40 minutes.
3. New impeller
4. Checked hoses for crimps
5. Blew water threw engine to check for blockage at each access.



Here are my top three thoughts on a culprit:

1. Through-hull - I don't want to accuse the yard that did the work with any wrong-doing, but I suspect that they may have used the wrong sea-cock. If they had used a ball valve ( like for a sink) instead of a straight pass-through valve, would that restrict the flow? I found a diagram illustrating what I mean.


2. Water-pump. - If my water-pump is getting old, could it have enough strength to run the engine perfectly from a bucket and not from the through-hull? That doesn't seem likely to me, but if the fix is a new/rebuilt water-pump, so be it.

3. Waterlift Muffler - Some kind of blockage? This is a distant 3rd for me since things work fine with the bucket brigade.


Other options?

It has been suggested that it could be a blown head gasket. That was my first thought but with the successful bucket test, I am doubtful. I've checked the plugs and they are all suitably 'sooty'.

Any thoughts would be appreciated!

Thank you,
__________________

[JOHN COOKSON]

Take the hose off the water pump inlet and leave it connected to the through hull and support it in an upright manner so the opening is in line with the through hull and above the water line. You can use another length of hose if the one on the water pump is too long or short.
Open the through hull and run a piece of rebar or a screwdriver down the hose and through the open through hull.
This way you can be sure the through hull fitting is open all the way. The through hull may be just a little open and still pass the "suck and blow" test.

TRUE GRIT

[tenders]

As you explain things, it seems like the only two culprits left are the through-hull...and the HOSE.

Why not replace that hose in case the act of sticking it into a barb is causing the rubber inside to bunch up and block the flow.

When it works, is the bucket at or below the waterline? You could also have a worn water pump housing that needs some head pressure to function, which it gets if the bucket is above the pump.

I do not think the type of valve has anything to do with it.

(Sorry, not going to add rebar to my boat toolbox! Just not happening! A screwdriver will just have to suffice!)

[ndutton]

I had a situation a few years ago with growth up inside that occluded the thru-hull to the point there was very little water flow. If that's the case here True Grit John's roto-rooter exercise will do the trick.

My solution was to replace the thru-hull with the next size bigger and slather bottom paint up inside. I further refined it to add a flow sensor to my alarm system (discussed here) and finally enhanced that to the EWDS.

Now it's no raw water flow = alarm buzzer + green panel light well before overheating.

[Fodder]

Thank you for the quick replies. The bucket was definitely above the pump but I don't think was above the waterline. There is good suction in that setup. I'm not a big fan of replacing parts without knowing if it's necessary, but I think it might be time for a new pump and the new MMI 502 flange pump looks like it's a definite upgrade.

I'll do the test of the through-hull as well. I need to find a piece of 'flexible rebar' in order to get through the pipe and through-hull as there isn't a lot of clearance above it. I suspect a coat-hanger might suffice. :-)

It's never a dull moment. Thank you again for the advice.

[romantic comedy]

I doubt that it is the water pump. There is a restriction in there.

Try the ram rod, if you can. Also try a hand pump to suck water thru the filter and sea cock. The seacock is below the water line right? It should flow a good amount of water when it is open. Just try that. Do you get a gusher. Fresh water right?

You can also hook the filter to a hose to see how the water flows thru it. Can hook the hose to the sea cock, and flush that too.

[tenders]

Bucket above pump = positive "downhill" water pressure with a minimum of priming effort.

Loop in hose above waterline between intake through hull and water pump = if pump is worn, potential problem with water needing to be sucked "uphill" and around loop by pump.

[67c&ccorv]

If the second photo in your first post is the thru hull fitting for your engine intake then what you have is a boat waiting to sink and an engine that will flood with cooling water if you crank it too long.

And by God - what sort of pipe is that clamped on there with one hose clamp...please tell me it isn't plastic electrical conduit???

There is no way that thru hull comes close to ABYC standards for thru hull fittings.

[JOHN COOKSON]

And by God - what sort of pipe is that clamped on there with one hose clamp...please tell me it isn't plastic electrical conduit???
There is no way that thru hull comes close to ABYC standards for thru hull fittings.

It's even worse than this.
Reread post #1 and look at the second picture. There is galvanized in contact with brass. The galvanized steel is already starting to corrode.
This needs to be fixed now before the boat SINKS.

TRUE GRIT

[yeahjohn]

I replaced my old water pump that seemed to be awesome, until it died a slow death of creeping water temps with what I thought was good output. The new pump, pumps. I have not had single issue with a warming engine sense I replace the pump last year. I think it is easy to forget how nice a strong water pump is to have until you replace the old one.

[Fodder]

Man, you are right! I'm so focused on trying to troubleshoot the engine overheating, I missed the single clamp on the sea-cock. Disaster waiting to happen. I am going up to the boat tomorrow and have to meet with the boat yard to go over my findings. Every time I turn around there's another issue. Sigh...

My advice to you all, if you are going to be struck by lightning....don't.

[zellerj]

new cam shoe

If your pump is old, your pump cam shoe is probably worn. You can replace the pump cam shoe by calling Oberdorfer 800 448 1668. MMI has a cam shoe for $40, but I remember spending under $8 for mine from Oberdorfer.

Best,
Jim

[ndutton]

My advice to you all, if you are going to be struck by lightning....don't.

And be careful who you allow to work on your boat. I haven't re-read the thread but I think I recall the single clamp and galv fitting were courtesy of the yard. Not knowing as in the case of an uninformed owner is one thing but pro's charging professional rates is quite another.

In addition to cam shoe wear affecting pump performance there is also cavity depth wear. I've been able to remedy this on two old pumps by sanding the face where the plate attaches but it's not for everyone. Keeping it dead nuts flat takes a delicate touch.