Head Stud Repair

[bigal]

Found the problem causing the leak at the thermostat housing studs; the thermostat housing has visible cracks in it. I believe it is an original casting and cracked when being torqued. Have a MMI housing on order. Hopefully this is the last f-up before launching.

[edwardc]

Found the problem causing the leak at the thermostat housing studs; the thermostat housing has visible cracks in it. I believe it is an original casting and cracked when being torqued.

More likely is freeze damage from improper or late winterizing at some point in its life. I had one with cracks on both sides from the stud hole to the cooling passage due to freeze damage.

[bigal]

That is exactly what mine looked like, but before the teardown it was not leaking. I had it bead blasted and some rusted thru holes appeared through the housing near the mounting holes that coincide with the cracks. I will post some pics when I get a chance. This was just another cast iron part that had rotted through. I should have known.

[bigal]

Her is the rotted thermostat housing.

[Marty Levenson]

good news...

...is that it's easy to fix!

[bigal]

Got the MMI thermostat housing and the bypass valve kit, installed them and the A4 is running as well as ever. I am running RWC, no thermostat right now and hope to control engine temp with the bypass valve. We are having our Pearson 36 launched tomorrow in Lewis Bay, Yarmouth MA,

[bigal]

Launched successfully, of course mooring was not in and we picked up a mooring at which we almost immediately went aground (in muddy bottom); ended up waiting out the tide for 5 - 6 hours while the mooring was installed. The A4 runs well, but doesn't register a temperature above 100 degrees (no thermostat yet) and smokes a little when running at RPMs above 1800. Will add a quart of MMO next time we go out, but this is an old block with compression on the low end of the scale and is probably blowing oil by the rings. I guess this Overhaul thread is complete (successfully) and I may be posting in the Cooling discussion group to get a grip on the nuances of getting the RWC system to run at a more advantageous temperature.

[ndutton]

Your temperature is expected with RWC and no Tstat. I had a Tstat with RWC and the engine thought it was running above the Arctic Circle, the needle rarely moved off it's lowest reading, 100 degrees.

[Baltimore Sailor]

I'm not sure whether to be jealous or not of these low temps. In the past year I've put in the new water pump, rebuilt my entire hot section, replaced the exhaust manifold, and done a muriatic acid flush.

I still run around 180 even with my bypass valve complete closed and sending all the water through the block, and it even trended up around 190 on a very long run home (2 hours) at 2000 rpm, which is just about my optimum cruising rps. I get 5.7 kt or so at that speed on a 28' boat.

The engine runs and sounds great, and the water batches like crazy out the exhaust, but the relative high temps puzzle me.

[JOHN COOKSON]

Baltimore
Are you RWC?
Somewhere I've seen a series of graphs in the forum that plot hose size and engine RPM vs water output through the engine.
As an approximate frame of reference I hooked a hose to the manifold output and stood in the cockpit with the other end in my hand, revved the engine up and shot a stream of water into the cockpit of my neighbor's boat.
I suppose you have been down this road already?
I run at 150* cruise and close to 160* when I idle back from running at cruise for a while. I consider this to be normal.

TRUE GRIT

[Baltimore Sailor]

Well, no, I haven't attempted to spray my neighbor's boat with water.

My hose sizes are as described in the A4 manual. I can't remember off the top of my head what they are, but they're the standard.

I thought one time that maybe the intake was blocked with growth, but that's not the case.

Can running rich cause an overheat condition?

[bigal]

John - I am running RWC, no thermostat, with a bypass valve and check valve (MMI kit). I wanted to make sure we didn't overheat during the launch so I didn't introduce a thermostat into the mix, but will add one soon. Hope to achieve the 150 - 160 degree temperature that you report.