How much water out exhaust?

[Rbyham]

Having run my engine only on the hard I had a question about how much water should exit the exhaust? I see it burp every 20 seconds or so and basically trickle in between. Is this normal?

[Mo]

Is your temp gauge working? Mine is RWC and batches about every 4 seconds, has a vetus underwater muffler, no thermostat, and the by-valve opened about 1/2 way...so I do allow water to be pumped through.

-are you noticing any steam with the batching?
-what type of exhaust system is in the boat?
-is your temp climbing up at idle?
-lets say you have a 5 gallon water jug to draw from...how long does it take to use it?

I did work on a friends boat a while back that had decreased water flow and some steam with it...T-stat caused that issue. Other causes could be:
-check impeller to ensure intact and the correct one installed.
-there have been cases, not too uncommon, where the impeller broke up and ended caught in the elbows just after the pump on the engine side...restricting water flow.
-manifold outlet can have rust corrosion restricting water flow.

It is still too cold here for me to fire up the engine and pump out my antifreeze. Perhaps in the next week or so I could do that and get you an idea of how long it takes to pump through 5 gallons of water.

[Mo]

I see it burp every 20 seconds or so and basically trickle in between. Is this normal?

Do you have a stand-pipe and a fairly straight run out of the boat without loops etc? A steady trickles means some cooling water is always moving, the burp is clearing out the stand-pipe or muffler. Lets see what guys with stand-pipes have to say.

[marthur]

Here is the output curve for the MMI pumps as posted by Don M on this site. The Oberdorfer pumps with the larger cam shoe will be similar. Older pumps might have worn cam shoes and were in fact built with a thinner cam shoe that is currently sold on the Moyer site, so their output is somewhat less.

Upshot, you should be pumping a gallon or two a minute at idle. Suggestion: Put a known quantity into a five gallon pail (say by filling it full or putting in several one gallon jugs). Put your pump intake hose into the bucket and measure how long your motor takes to pump it out.

[Mo]

It is still too cold here for me to fire up the engine and pump out my antifreeze. Perhaps in the next week or so I could do that and get you an idea of how long it takes to pump through 5 gallons of water.

It's a good thing I didn't try that. It was -17 C here this morning -31C with the windchill...that's our worst week in Jan weather. Snow in the forecast for the next couple of days so tomorrow I'll put the plow on the truck. I was planning on sanding the bottom of the boat this week....guess not.

[ILikeRust]

Here is a short video showing the exhaust batching from my boat while running on the hard. This was the first running of the Atomic 4 right after I did a full tear-down and rebuild, which included converting to FWC and a brand-new Moyer raw water pump.

[YOUTUBE]J-ts7GJ1oHg[/YOUTUBE]

[olebiker]

-17 C here this morning -31C with the windchill...
That's nothing...it was 78F here with a low of 52...Dang right chilly. Love this place!

[romantic comedy]

There is no batching with a standpipe. The water just runs out consistently.

[toddster]

My old standpipe "batched." The new one doesn't. It can also depend on how the exhaust hose runs and if you have an antisiphon loop.

The old one had a low water injection point and a high exhaust port. The new one is the reverse.

p.s. It looks like there is more water coming out, when there is no batching, even though it must be exactly the same.

[Kelly]

Exhaust flow video

Here's a link to a rather long video that shows exhaust flow while in the water at two RPM settings.

Hope this helps. You can see very regular water flow with my stand-pipe-followed-by-mixer setup, even at low RPM.

Kelly

[dthibaul]

Mine Like Bill's

My flow is just like Bill T's at idle- burps with flow in between.

Don

[67c&ccorv]

Having run my engine only on the hard I had a question about how much water should exit the exhaust? I see it burp every 20 seconds or so and basically trickle in between. Is this normal?

What year is your A4?

[Ajax]

Having run my engine only on the hard I had a question about how much water should exit the exhaust? I see it burp every 20 seconds or so and basically trickle in between. Is this normal?

The burping or batching isn't unusual, but the interval seems a bit long.
I advocate the aforementioned flow test with the 5 gallon bucket.

Don't you have a temperature gauge? If not, you can also buy an inexpensive IR thermometer from Harbor Fright or Home Despot.

Does it pump water more aggressively at higher RPM's?

[Rbyham]

Subsequent to thread start I have happily splashed. All is well. I did have to get warm water return valve closed before she would spit out the back but now she does like a pro. First time in water after 8 years storage and she fied and ran us an hour away to slip with no temp issues . I can see why you folks all love this little engine.

[Mo]

So Cool,
Have a great summer...play safe!