Cooling system problems. Need some help.
I recently purchased a 1975 Downeaster 38' Cutter, re-powered in 1994 with a Yanmar 4JH2E. It only has about 900 hours on the engine, but has been sitting unused for a few years now. I live in Orlando, FL but the boat is in Inglis, FL near Crystal River in the Big Bend area at the sellers dock. He is being kind enough to let me keep it there until I get it in shape to take it elsewhere. So I am limited to making weekend trips up there for now.
When we did the sea trial, the engine performed just fine. We ran it up and down the river for almost 3 hours with no problems at all. I had not taken her out since then (about a month) and have just been doing a lot of cleaning and work replacing the running rigging. Two weekends ago I decided it was time to take her out on the river (its on the Withlacoochee River) and show some friends a good time. Before we went out, I checked all fluids, cleaned out the raw water strainer and topped off the coolant. I noticed there was no rubber gasket or anything on the cap of the raw water strainer, just a metal plate. I didnt think much of it at the time, but now I wonder if there should be one.
The engine ran just fine for about an hour up the river. At one point, I revved it up to 2,800 rpms to see how it responded at cruising speed. Soon after my heart sank as I noticed steam (of course I first thought it was smoke and we were burning down) gushing out of the engine room. I quickly shut it off and had to release the anchor for the first time on the boat (something I needed to learn soon, but in less stressful circumstances).
The cap on the expansion tank for the cooling system had popped off and the cooling water was steaming everywhere. I also noticed that the air silencer had popped off and was hanging by a hose. I had checked it before we left and may have not secured it correctly. So I topped off lost coolant and let the engine rest for a while.
It was getting dark soon and we needed to get back. The engine cranked up just fine but after a short while the temperature was running high. Right before we got to the dock the cap on the expansion tank popped off and once again steam goes everywhere.
We had to go back to Orlando for the week so I did some research and stupidly realized that I didn't check if water was flowing out of the exhaust at all. I had also remembered that the belt was pretty loose, so those were first on the list to check when I came back. I would make sure to double check how I closed the water strainer.
So I go back to the boat this previous weekend. I tighten the belt after much hassle and checked to make sure the raw water strainer is tightly sealed. I then started the engine and first checked to see if any water was coming through the exhaust....none :( . So my guess is that the problem lies in the raw water circuit somewhere, correct?
I planned on checking and replacing the impeller, of which the previous owner already had a new spare. I soon realized that the impeller is in a hellish place where I can only fit one arm with barely enough room to move a tool. Removing the cover plate for the impeller was tricky, but I did it without loosing my cool. Then I realized that I would not be able to take the impeller out with any ease. I hoped to use the 2 screwdriver method to pry it out, but there was no way I could get two of them in there. I spent the majority of my day getting frustrated :hothead over figuring out how to get the impeller out, and didn't get much else done.
The only other thing I checked was to make sure there was nothing blocking the through-hull. I popped the inlet hose from the raw water strainer and was able to suck water through, so that was clear at least.
After leaving my dad asked if I checked to make sure the impeller was even turning after the engine was on...no, I didn't check:confused: .
The boat is old, but the engine is the one thing I was happy to have working fine. This completely has left me in the dumps emotionally, and then to cap it off I got cut to part-time at work this week amidst a bunch of lay-offs. Im lucky I still have the job, but loosing 20% of my salary takes away the extra money I was using each month to get the boat in shape.
So that is where I am. What steps should I take this weekend while I am there? I assume to make sure the impeller is even turning by running the engine with the cover off? Do I start to just pull hoses at various points along the circuit to see if water is flowing? Am I limited to buying an impeller puller or is there a cheaper tool I don't know about?
Any help isolating the problem would be appreciated. I hope I can get this done without paying someone to come out to the boat. I am willing to learn and do the hard work, but need some sage wisdom.
You have done a pretty good job of troubleshooting the problem. Since water is getting past the thru hull, and the water strainer is clear, the the problem is most likely the water pump.
You fixed the loose belt, so that leaves the impeller as the likely problem.
On my boat, I can get to the pump fine, but the pump cover is on the back side, so I have to remove the pump to change the impeller. I disconnect the hoses and remove the pump on its bracket.
It's easier to change the impeller working on a table. Be sure to lube the new impeller (olive oil works well) before you put it in. Make sure you retrieve any broken impeller blades that might be loose in the case or output hose.
I recently had
I recently had a brand new, maybe 10 hours on it, Yanmar impeller spin the center hub. It looked perfect the first time I checked it. If this is the case, replace it with a Johnson brand impeller. Easy to spot, as the Johnson has a screw which goes all the way through the impeller, not just the pin. Apparently this is not a real unusual happening, so from now on I will only have the Johnson impellers on my boat.
And I'm betting that you never, ever leave the dock again without making a casual glance over the stern.....:)
i take it that this engine is cooled by sea/river water pumped around the engine , as to a close system were it has a heat exchanger ????
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