New guy

[TerryB]

Hi,

I have a 1976 C&C 27 with a late model A4. The motor has rwc and been run in salt water most of her life. I launched her last month and the distributor disintegrated. I was able to remove the shaft from the block with torches and tapping. I replaced it with a new electronic ignition distributor.

Then the water jacket side plate blew out due to corrosion. So a bought another A4 for parts mostly. Replaced cover and brass drain. Engine runs sweet now but water flow was low. Removed thermostat and flow was good. Replaced impeller and did a test run. After 40 minutes the engine shut down due to overheating. Lots of steam. I’m stumped.

[Al Schober]

Terry,
First, welcome to the Forum. Hopefully you'll get some good advise here (if not from me, then from someone else - grin).
Overheating is not uncommon, particularly with raw water cooled engines. The blocks (and some other cast parts - not the side plate cover) are a high nickel cast iron and quite corrosion resistant. But even without corrosion, the raw water and heat will precipitate salt in the engine, tending to block things. A common place for blockage are the small passages between the block and the head by the valves.
Personally, I like running without a thermostat. Running the engine cool is not a cure-all, but I prefer the consequences to those from overheating. I'd also install a valve in the bypass line so you can control (or shut off) the bypass flow.
In your case, I suspect what happened is that removal of the thermostat and the new impeller caused increased flow - picking up all sorts of loose gunk inside the block and flushing it out. However, it just moved it somewhere else where it clogged things up. Could be anywhere downstream, but my first guess for a clog would be the outlet elbow on the manifold. Keep in mind, you should be able to blow through any component of the system with little resistance (including the block). The pieces are all connected by hoses. Disconnect them and try blowing through them individually - you'll quickly find the culprit (and perhaps some shaky hose clamps).

[Mo]

I agree with Al...

My thoughts on this one:

I would go right to exhaust manifold outlet. Remove the hose off the outlet closest to the hot exhaust section (the rear one) and try to put your finger in it. It may even look like there is water there so stick you little finger or something down in the hole and ensure it is clear. Another hint to this being the issue is if there was a smell of rubber. This would occur when the rubber on your exhaust hose heats up with the disproportionate amount of water and hot gases in the exhaust. If that turns out to be the case you will need to remove the exhaust manifold and clean it all out. Remove carb, choke attachement, throttle attachment. Disconnect hose off the end of the hot exhaust. If the hot exhaust breaks during removal it needed to be replaced anyway...again, not a major. Remove the 3 bolts holding the manifold...slide it to the side an inch or so to clear the studs and then move the whole manifold and hot exhaust forward and toward the cabin...keep it all together and pressure wash the manifold clean ...you could bring it to a rad shop either and have them clean it out...should be easy for DIY er though.

If that checks out double check the impeller. Some impellers don't fit correctly and leave a space between the cover plate and the impeller itself...there are cases where they were actually the wrong size. MMI has the right gear. It needs to be a tight fit. If there are wear score marks on the plate you can actually secure the plate and sand it with a course sand paper on a random orbital sander until flattened out...then put it back on with gasket or permatex and it will work better.

[Sam]

Might have put impellor in "backwards" and not sealing on pump backplate. Will look like pretty good flow but will not be enough to continuously cool engine. Impellor has tiny little dimples circular core that must be installed facing pump. Just a thought.

[ndutton]

I did not read where you blocked the bypass when you removed the thermostat.

[TerryB]

Update

Thank you all for your input. So I flushed engine with two gallons of muriatic acid. First flush let soak for 15 minutes and then repeated before flushing with sea water. There were lots of brown water discharge. Ran engine at medium revs to flush but engine began to over heat again after 15 minutes.

So I took off hoses and checked the water lock muffler to see if it was,plugged. It was clear, looked new. The exhaust hose was in bad shape so I removed it. I will also replace the hose leading to the water lock muffler. Will check fitting exiting water manifold tomorrow. New exhaust hose arrives tomorrow afternoon.
I will also block water flow to thermostat bypass.

Will look at impeller to see if I put it in backwards. Never knew it only worked one way?

[ndutton]

I will also block water flow to thermostat bypass.

Without blocking the bypass you have no block cooling with the thermostat removed, no block cooling at all, only manifold.

[Sam]

I think our west coast guru ndutton zeroed in on the real issue of your current overheating. Couple of thoughts - I have 1966 early model A4, Morgan 34, which has been in fresh water Lake Michigan its' whole life and came with a 140 F Dole thermostat. FYI decades ago I questioned this low operating temperature and it was explained to me that @ 140 F and lower salt does not precipitate out of sea water. Later on the late models the A4 engineers moved the limit to 160 F and changed the cooling flow etc. Think this when some salt blockages started to occur in the community.

My question to all is can an A4 really shut itself down from over heating without potentially damaging/warping valves, guides, springs, head gasket etc. I installed an OPSS but not any kind of temp alarm. When motoring I'm glancing at the gauges. Couple of times when some debris was picked up or impellor fin broke I shut it down, sailed in and then used the somewhat cooled A4 for the last minute of docking. An alarm would be reassuring and informative - any suggestions or guidance on brand or installation? Sorry if I ventured into a new topic but I thought it might be useful info. thx

[Peter]

An alarm would be reassuring and informative - any suggestions or guidance on brand or installation?

https://moyermarine.com/product/the-engine-warning-and-diagnostic-system-ktas_01_564/

Peter

[roadnsky]

Sam-
Please note that to use the EWDS, you'll need this base alarm as well.
The beauty of the EWDS system is that you can start out with just the basic alarm if you don't have the boat bucks to go the full monty.
And then add the full alarm to get the detailed warning (and comfort) the EWDS gives you.

Just give Ken (in parts) a call and he'll walk you thru it.


EDIT - I just realized... how ironic that the system Sam is looking for was invented by our "west coast guru".... Neil (ndutton)

[TerryB]

Update 2

Well a little progress today. Then slapped back down to reality. I replaced the exhaust hose with a new one. I checked the impeller for dimples, there were none and te new one I put n a month ago is from MMI. I also put the thermostat back in.

I then installed a diverter valve after the tee on the engine cooling side jacket panel just before the thermostat to divert more cooling water into the engine. Checked for obstructions on the hot end of the coolant manifold and it was clear.
So I started h up and it ran fine but my temperature gauge is broken. Took it for a run and could touc the top of the thermostat the whole time. Seemed like was off to the races then the engine quit and would not restart. Smoke coming from back of engine area and coil was too hot to touch. So......what’s up now.

I did put a new distributor with electronic ignition and this is the first time I ran the engine over 30 minutes. Back to scratching my head.

[ndutton]

I did put a new distributor with electronic ignition and this is the first time I ran the engine over 30 minutes. Smoke coming from back of engine area and coil was too hot to touch. Back to scratching my head.

Please tell us about your coil:
Age
Brand
Internal resistance
Potting material

[TerryB]

Coil

I will take it off tomorrow as it was too hot to touch and I was fed up and needed a beer lol. I just bought the boat and the learning curve is steep. Do coils need a resister?

I’m not even sure if it is the coil but need to start somewhere.

[ndutton]

Do coils need a resister? I’m not even sure if it is the coil but need to start somewhere.

With electronic ignition, some do. Give these threads a read this evening so you can return to the boat with new vigor:
http://www.moyermarineforum.com/foru...ead.php?t=5748 and the Cliff Notes version http://www.moyermarineforum.com/foru...ead.php?t=5845

[TerryB]

Won’t start

Well changed coil. Turns over but won’t start. Was running fine. Lots of gas.