ongoing overheating problems

[mrxitmt]

I replaced the thermostat after my last post and the temp seemed to stabilize so I thought the problem was solved.went out the 4th of july but was close to home and didn't even get up to cruising speed.All OK .Then I went on vacation.Last saturday 4 of us went out just for a run .got about a mile away (temp guage at 150 160)..watched the temp the entire time .At a sudden loss of power we turned for home.temp still reading good.started making tapping noise .put it in neutral engine cut out . opened hatch engine HOT water boiling in thermostat housing.
The problem is ..we cant find the smoking gun...outdrive Impeller looked ok (will be replacing it anyway) pulled the circulator pump and opened it up and that doesn't look bad either!? I'm very upset and stressed out to be having all this trouble with a boat that i just bought

What else should I be looking for

96 2400 scr alfa gen 2

[mmwjr]

Exhaust Risers and manifolds. If these are blocked the water flow is restricted. First replace impeller, IMHO inspecting is a waste of time if you go through all te work to pull it out why not spend the ~$30 and put a new one in. They are only good fo 2 years after that asking for trouble. If impeller doesn't fix then pull a riser and inspect.

Get yourself a infered handheld thermal gun and measure temps on t-stat, risers, manifolds, ... looking for hot spots.

How many hours are on the engine? Exhaust is good for no more than 500 typically but this depends on fresh vs. salt water, flushing the engine helps but in the end everything wears out.

[pascavone]

obviously a raw water problem,not to worry as you can trouble shoot water flow with a garden hose.

So,
1. hook up your outdrive ears, and pull the hose off the inlet hose on the raw water pump. See if you have garden hose water coming out. (note: all stock engines are RH right hand or counter clockwise rotation, maybe sure the input water like is on the bottom of the raw water pump, and not reversed).
2. Hook up raw water pump again, and check flow at fuel cooler plastic plug.
3. check flow at thermostat housing. (make sure thermostat is not installed backwards).
4. pull cooling hoses of manifolds and check for flow.

see if its runs cool on the garden hose....

[mmwjr]

Pas when you are sawing raw water pump I am assuming you mean the circulating pump on the front ofhe engine, his boat has an Alpha so the raw water pump is in the outdrive.

Therefore:

1. hook up ears to O/D remove water inlet house from transom assy to t-stat to check water flow.
2. Being a 96' don't think he has EFI but has a carb so no fuel cooler.
3 and 4. are kind ofthe same as water to manifolds come from t-stat housing. Most t-stats can not be installed upside down by design. Crown goes up and if upside down bottoms out before flang is flush with housing.

[mrxitmt]

After some more checking I think the tstat housing may be bad (one piece)...The incoming water is not going to the circulator pump . I am going to check it this evening

[mmwjr]

Here is a diagram of the cooling system. This is for a bravo application, since you have an alpha the hose going to the water pump in this diagram will go directly to your transom housing.

[shrew]

This is a little confusing. Water was boiling? 212F. Temp. guage read 150-160f? I think normal operation is 175F. Inspecting the impellor should be fine. If there are missing fins or there is cracking in the rubber, then replace it. Otherwise it should be fine. Either the fins are there to sling water or they are not. Cracking indicates the fins are going to fail in the neat future. Better to replace it before it fails than chase through the system for all the rubber parts.

Risers and manifolds can also cause overheating issues. As does blocking pick ups.

[mmwjr]

Shrew I agree that if the fins are all there and have no signs of cracks the impeller is probably Ok but after draining the gear lube to seperate the lower half of an Alpha drive you are spending ~$20 for new lube why not add another $30 and not have to worry about it for 2 more years.

Open systems are pretty simple need to verify no blockage from input to output (debris in pick up, rust scale in engine & exhaust) , working pumps (raw and circulating), good t-stat.

Was water boiling? I have seen closed systems that were low on coolant where the temp guage showed normal yet the system boiled over. Best I can tell is a air pocket formed near the temp sensor giving false reading.

Either way sounds like it was having issues. Just hope no engine damage occured since he mentioned a low of power.

[mrxitmt]

It gets worse . Installed new water pump in lower unit. Checked everything for blockage .Checked Circulator pump. Bought an infrared thermometer . Finally had a chance to take her out today. We put her through the motions and everything looked good.Got back to the dock left it running .Opened the hatch to do one more temp check....WATER in the hole... at the rear of the motor there was water running out mixed with oil...shut it down .....2 gallons of oil water in the crank case....I GIVE UP.

[pascavone]

time for a compression test, as you might have a blow head gasket, not to big of a deal.

You could have a cracked block or leaking manifolds.

time to get a mobile mechanic in to look it over.

[mmwjr]

Not a good way to get beack into boating.

As Pas said start with a compression test. What ever you do don't let water sit in the cylinders over the winter or the engine will be done for sure.

Do you have any experience with pulling heads?

[pascavone]

water is the engine will not hurt it as the oil is coating everything, in the short run.

If you had that much water, then I'm surprise the thing ran.

The only way that much water could get in the engine that fast is the manifolds, as it is pumped in.

A blow head gasket, or cracked block would not be the severer.

Pull the riser off and look for rust on the inside of the exhaust ports on the engine.

[mmwjr]

Water getting into the cylinders from a bad manifold can't get into the oil easly either it has to get past pistons and rings which if are in normal shape will only let small amount past and not a gallon. I question the gallon comment, that would mean 1 gallon of water plus 5 qts or over a gallon of oil. Water in oil becomes foamy which may look like a lot more water than on thinks.

[pascavone]

my engine had a ruff idle, that cleared up after a few minutes.

In my case is the water filled up the cylinder over night, and then the compression stroke push the water into the crank case, as water dose not compress, as it is hydraulic.

also, the water filled the intake manifold gallery as the valves are open on intake, as the manifolds where higher then the whole engine.

Luckily, it was confined to one side of the engine, and I only bump the engine on the starter, but that did bend two pushrods, because the exhaust valve could not open with the water in the cylinders.

My attempt at the first hydrogen boat engine was not successful.

actually, the same thing happens on old radial engine airplanes for WWII, the bottom inverted cylinder bucket, would collect oil over night, then they would start the engine and the oil would not compress, and blow the cylinder off the engine.

[mmwjr]

2 bent pushrods, I have also seen bent valves and connecting rods from trying to compress water. But still a gallon into the pan?

Anyhow let's see what he has to say, that is if he isn't so mad he can't find the words

[pascavone]

well, my push rods lucky only slip out of there groove, since I only bumped the engine on the starter.

[mrxitmt]

The deal is... the engine was running fine when I opened the enging hatch to check temps with a infrared thermometer ..The bilge was full of water!!!I looked back by the flywheel on the starter side....Oily water was rushing out of the engine I couldn't tell from where (still running fine )Then I shut it off .I pulled the dip stick to see brown sludge way above the full mark..Later I pumped almost half of a 5 gallon bucket of this sludge out of the crank case. I will start dissasembly tomorrow..And yes I am very upset ..disapointed ..Depressed .I thought I was buying a good reliable (new jasper long block)beautiful boat last september..I got one good trip out of it..I have the knowlege and equipment to rebuild the whole thing if I have to.I just wasn't thinking I would have to do it so soon.I'll let you all know when I find out what happened.Thanks for your concern and suggestions!
Rick

[pascavone]

hey,

its still could be your manifolds dumping raw water into the engine.

The oil is only the result of the crank case full of water, and its over fill coming out the vents. Its oil cappuccino.

I would guess, that the engine is fine from jaspar, its the old crappy manifolds they reused causing problems.

Disconnect the raw water lines to the manifolds, one on each side, or better yet, one at a time, and run the engine with the raw water going over board, and by pass the manifold cooling for a bit, and see if that solves the problem.

The goof balls did the same to me on a re install and reused this riser block, and I had the same issues.

[mrxitmt]

I have to ask ...how could the crankcase fill with water with the motor running (oil was fine before we went out)..Now for an update I went out to crank the motor and get the new oil I put in circulated thru I figured it wouldn't start but it started up and ran fine 20 seconds and I shut it off I pulled the riser..It's rusty but not totally clogged. The plugs didn't look like there was water in the cylinders.Manifold will come off next.

Rick

its still could be your manifolds dumping raw water into the engine.

The oil is only the result of the crank case full of water, and its over fill coming out the vents. Its oil cappuccino.

I would guess, that the engine is fine from jaspar, its the old crappy manifolds they reused causing problems.

Disconnect the raw water lines to the manifolds, one on each side, or better yet, one at a time, and run the engine with the raw water going over board, and by pass the manifold cooling for a bit, and see if that solves the problem.

The goof balls did the same to me on a re install and reused this riser block, and I had the same issues.


[/QUOTE]

[pascavone]

the manifolds, spaces, and elbows are all above your engine like a toilet tank, and are draining down thought the valves, anyone that is open.

Half open valves, will fill your intake gallery.

Funny, in Detroit the 1970's they fooled around with water injection to boost horsepower.

needless to say, any water in the cylinder at 1500 rpm is going to end up in the oil pan in short order one drip at a time.