Since the purchase of ‘Magic’, a 1985 Freedom 32 fitted with a Yanmar 3 GMF, it has been impossible to exceed 2,300 RPM’s without the engine overheating. This made a journey from Oriental, NC via the ICW to Norfolk, VA very tedious.
Prior to making the journey, the boat had been hauled and the through-hulls checked for operation and any restrictions cleared. The Raw Water Strainer was cleaned and the Raw Water Pump impeller checked, the outlet from the Raw Water Pump was also checked, along with the tube-stack of the Heat Exchanger for any broken impeller bits or blockage caused by calcification. As the following picture shows, all was OK.
So, after replacing the o-rings and diverter gaskets, the heat exchanger was reassembled. But this didn’t prevent the overheat problem.
‘Magic’ made it to Norfolk, VA, I also found that I may have bad fuel during the crossing of the Albemarle Sound, that is another story though.
Well, this last weekend, after thinking about the problem and discussing the problem with colleagues in the marine business, I found that Yanmar engines, fitted with the alternate ‘high-rise’ exhaust elbow have a recurrent problem with the 90 degree raw water injector on the exhaust elbow shown here.
They have a tendency to become restricted as the water flow through the elbow slows and the salt and minerals come out of solution and deposit themselves in the elbow and show in the next pictures.
It looks like the restriction is causing a 70% plus loss of water flow which was worrying as I had not noticed a lack of water flow out of the exhaust. I put this down to the function of the water-lock muffler and the length of the exhaust run on the F32’s with the engine being mid-mounted under the galley sink like on the Catalina 30’s.
Here is an end on shot of the fitting clearly showing how badly blocked it had become.
I decided that just cleaning the fitting was not enough. Apparently, some Yanmar engines with this water injector require the fitting removed and cleaned frequently, sometimes more than once a year!! It is a simple fix and not difficult to address as ‘Annual Maintenance’ but after contemplating the issue, I decided to replace the 90 degree fitting with a straight fitting as shown here hoping for a permanent fix.
Incidentally, the hose connected to the fitting is from a siphon break that is mounted high up under the galley sink and you can see the input end to the siphon break on the back of the heat exchanger.
Well, I ran the engine in gear at the dock for some 20 minutes which would have normally caused the overheat alarm to sound. Then after a trip to the marina pump-out station, leaving the engine running while pumping, I took a quick trip out into Chesapeake Bay. Went out about a mile or so out of Little Creek without any alarms, so on the return trip I opened the throttles and made 3,400 RPM’s on the run in. Hooray, no alarms and no exhaust smoke It seems ‘Magic’ may be a less over-propped than I originally thought and is no longer on my list of ‘things-to-do’.
Have I achieved a permanent fix? Time will tell.
This is a very easy fix, the cost, if only cleaning the elbow is nothing and takes between 30 minutes and an hour.
Incidentally, the corrosion that is visible is predominantly on the rear of the engine and has been caused by the siphon break that spits raw water when the engine starts and stops as water flow starts and stops through the raw water circuit. A ‘splash guard’ is on the ‘to-do’ list to prevent the engine getting splashed. The engine will be ‘pulled’ in the spring for new mounts, de-rusting and paint.
If I might make a suggestion. I’ve found that when you have that much blockage in the little elbow water inlet there is often quite a bit waiting in the elbow itself. Those elbows are iron and when they rot out and fail they have the potential to dump salt water back into the engine via the exhaust valve on that number three cyl. They are a mother to get apart most of the time and there are some left hand threads involved on the adapter to be aware of if you try to take it apart. Cleaning can be accomplished in a 5 gallon bucket with one gallon of pool acid (muriatic acid) and 4 gallons water. Try not to breath the fumes! But often the cleaning process can remove so much rotten material that the elbow becomes even more of a time bomb.
If you are achieving 3400 rpm wot then you are propped right. The tack can be up to 15% off at any point in the power curve right from Yanmar and I’ve always felt that getting within 300-400 rpm is adequate. I have a hand held tack we can put on it to see what it’s really doing if you are close by. I’m in Annapolis.
Ach! One more suggestion. Based on the amount of corrosion on your motor. There is an external oil line on that motor that’s made of steel. Those can get crunchy and rust thru dumping the entire contents of the engine oil. I’d give that a careful look. In the photos it looks like it might have been replaced at some point but not painted first. I always paint them with zinc chromate (I can see our environmental health team cringing) and a good couple of top coats of engine paint.
In fact it is my intention to get a new exhaust setup and as you mentioned, the threaded nipple does actually have a left handed thread on one end and a right handed on the other.
As mentioned earlier, I will be pulling (removing) the engine when I replace the engine mounts as the Stbd front mount has been swollen and weakend by a fuel leak from the secondary filter and the condition of the others is questionable. At this time I will thoroughly clean and de-rust the engine and initially treat with ‘Ospho’ before refinishing. I do appreciate the ‘heads-up’ on the oil line though, that could be an expensive failure.
I’ve also been told (by more than one engine mechanic), that, rather than idling a while and then shutting down the engine from low idle, you should idle a while and then kick the RPM’s of the (unloaded) engine up to around 2000-2200 rpm for at least 30 seconds and then pull the kill switch with the engine running at that speed.
Supposedly this will blow out the “loose carbon” which would otherwise “cook” onto the various parts of the exhaust system and minimize the deposit of unburned hydrocarbons on same (and pistons, I guess) as the enging cools. I’ve heard the latter described as “coking”.
I don’t know if this is sound information from an engineering standpoint or not, but it “sounds good” to me…and I had no problems with the Yanmar exhaust elbow on my prior boat after implementing this process…and none at all on the Perkins 4-108 in the past 13 years.
The elbow failure I was describing is corrosion due to hot salt water passing through iron. When they fail they tend to dump some water down into the number 3 cly (or number 2 on the 2gm) every time you shut the motor down. Pretty soon there are valve issues on that cly, loss of power, black smoke etc… I never heard of the rev it up just prior to shutdown but I can see that it might also have the secondary effect of blowing much of the water out of the aqualift as well.
Robert it sounds like you have a plan for your motor and I couldn’t agree more with it. Be aware that the motor mounts are different front and back. They look identical but you will find that they have different casting numbers in the rubber. I think on the 3gm it’s two 75’s and two 100’s but I can’t remember for sure.
If you get the bright idea of cleaning the whole raw water system by running muriatic acid through your engine (picked up by the raw water inlet hose from a bucket)…NOT A RECOMMENDED ACTIVITY…
Be sure and remove any pencil zincs in the engine & heat exchanger first. (replace them with the old/worn out ones that you “saved” for no particular reason). The zincs will last about as long (in the flowing-acid-bath) as they would if they were made from frozen sour cream.
Don’t do this IN the marina!! The fumes can wipe out your downwind neighbors, play hell with (other peoples’) wax jobs, polished stainless steel, exposed bottom paint, and lungs. Particularly if there is little-to-no wind blowing. Best go hide on a mud flat someplace where nobody can see what you’re doing.
Don’t just “try” to avoid the fumes…they can kill you. Muriatic is 5% Hydrocloric Acid…even a 4:1 dilution will react and fume significantly (particularly in the presence of calcium buildup).
I posted a whole long thing on this in the Yahoo group a while back. Search on “muriatic” and it will pop up somewhere.
I think someone also mentioned to me that they tried to clear a head clog with this solution and it ended up blowing up the lines or tank or something. Bad bad!
I think that Yanmar decided they didn’t need any zincs in that cooling system as they used “o” rings to isolate the exchanger… again memory might be flaky. Maybe due to too many muriatic acid fumes?
[quote=“THATBOATGUY”]I think someone also mentioned to me that they tried to clear a head clog with this solution and it ended up blowing up the lines or tank or something. Bad bad!
That would have been me, but the head wasn’t clogged, I was “simply” trying to get rid of the calcified buildup that was growing inside the waste lines.
The muriatic attacked the nitrile rubber in the pump, turned it into a shrunken crispy black “potato chip”, and I had no way continue pumping to clear the lines. The acid (which could no longer be flushed through the lines) continued reacting and dislodged enough stuff to plug the outlet end of the line.
The resulting pressure buildup blew the Y-Valve & the pump body to pieces. Anticipating what would happen (once I could no longer pump anything and hearing the reaction continuing in the black rubber hoses), I put a garden hose into the bilge and turned it on to dilute what I knew would inevitably end up there. It took about half an hour, by which time I had turned off the hose. The bilge pump handled the mess with no problems.
Replacing the “middle” of the waste discharge system took two days of my time and several hundred dollars.
Not one of the high points in annals of boat maintenance.
I now use pickling vinegar (regularly). I don’t expect to blow anything up with that.
Yes white vinegar is the way to go on installed systems. I do use muriatic acid on frequent occasions to clean heat exchanger tube stacks at work, you have to be careful with Yanmar ones though as some have an aluminum sleeve surrounding the tubes. Muriatic acid and aluminum is also a no-no.
I’m not sure what the machine shop uses in their tank but most of us gear heads learned by like age 16 that if you want to re-use your cam bearings you tell the engine shop about it before hand or your block comes back all clean with the cams missing! heh heh They have another tank for aluminum stuff.
I certainly learned from Johns mistake, even if I couldn’t remember the source. Don’t use it anywhere it might get contained. I worked with explosives for nearly two decades in the military ranging from .22 rounds to nukes so I have a deep lingering respect for what contained chemical reactions can do.
When I first got my Freedom a mechanic told me to change two thing periodically. The raw water impeller every year and the mixing elbow every five years.
I also have had continuing problems with over heating at 3,000 rpm, in warm water, and warm air. This year I added a 4" exhaust fan that seems to have eliminated the problem. I also measured the engine compartment air temperature in the upper forward starboard corner. It got up to 155 degrees F. Mechanic says it should be around 120. Trying to figure out how to get more air intake.
My wife thinks we should use the exhaust as a clothes dryer.
One thing that can increase engine compartment temperature is high output alternators, particularly when fitted with external regulators. Unfortunately this high heat also causes the output from the alternator to drop but by the time this happens it’s too late. When fitting alternators over 100amps we recommend a 4" intake and outlet for engine compartment ventilation.
