I'm thinking that perhaps I should clean out through hull for sea water to my yanmar engine. Is there a clean out snake or some easy way to do this while boat is in water?? I got worried when I cleaned out a lot of green grassy stuff from filter. Perhaps its covering much of intake? Does anyone know how much water is supposed to be flowing through a 3 GM 30?
How do you clean through hull while in water?
- Thread starter Ted10028
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Hi Ted. I suppose if you're worried about this, disconnect the intake hose from your sea water strainer (ours is above the waterline, make sure yours is, too) and run a plumber's snake through the hose and through the sea water valve and through hull. Likely not clogged as you say the strainer collects a lot of grassy stuff.
Some years ago our aft cabin electric toilet refused to bring sea water in for flushing. Turned out a fish, some marine critter or something decided to enter the through hull and could not back out and died. I blew the line clear with a city water hose, but the stink was something else.
As far as water flow goes, it should spit out some water at idle and increase with engine RPM. At least that is what our 4JH does.
Some years ago our aft cabin electric toilet refused to bring sea water in for flushing. Turned out a fish, some marine critter or something decided to enter the through hull and could not back out and died. I blew the line clear with a city water hose, but the stink was something else.
As far as water flow goes, it should spit out some water at idle and increase with engine RPM. At least that is what our 4JH does.
I'm worried about stuff growing in and around intake too. City water pressure and snake should do the job though! Thanks!
If the strainer is below the waterline, close the seacock, and remove the hose. Attach another hose that is long enough to go above the waterline, then flush with city water or snake it out.
If you have a strainer on the through hull, the bronze type with lots of holes, clean the holes out at the next haul out. Paint builds up in the holes and restricts water flow. It is an easy job, use a drill and an appropriate sized drill bit. A five minute job.
If you have a strainer on the through hull, the bronze type with lots of holes, clean the holes out at the next haul out. Paint builds up in the holes and restricts water flow. It is an easy job, use a drill and an appropriate sized drill bit. A five minute job.
I put a flow meter in line after my strainer for my 3GMF22. It was useful for determining any flow restrictions. That usually happened when the hose would clog up at the mixing elbow. The Yanmar service manual says the flow rate at idle is about 2.5 gal/min. That matched what the meter said. At 2800 rpm it's about 7 gpm. A few years later I upsize the raw water through hull from 1/2 inch to 3/4 inch just to add margin for potential clogs. It worked fine although the flow rate was still the same.
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I suppose I could hang a 5 gallon Home Depot bucket over the side and get a measure of how much water is flowing.
That works too. You could pull the hose off the mixing elbow and catch it there inside the boat if easier to hold the bucket. Have a second person start and stop the engine after a known amount of time.
if it seems to be overheating despite normal water volume throughput what would I investigate as possible causes?
mine seems to overheat only at full throttle. I assume if the thermostat were not opening it would overheat at any throttle level?
Not necessarily. There is a small pass through in the thermostat that may allow enough water through to stay under the overheat threshold or the thermostat may only partially open and until the engine is fully loaded it allows enough water to keep it below the overheat threshold.
Check the water pump impeller.
Pull the end cap off the heat exchanger and see if there is build up of scale on the tubes. I had a long 1/4 inch drill bit that fit loosely in the tubes. They're slightly bigger than the drill so I could clean them out without removing the entire thing. The rubber gasket was good for at least two removals. It doesn't take much build up to decrease heat transfer efficiency. The flow may look nearly the same. Also, check the fitting at the mixing elbow. Mine was a small bronze elbow that would clog over time with salts. Pull the hose and the fitting. Check for blockage. After I switched to a straight fitting it was easier to ream out with a screwdriver. If you still suspect blockage at the through hull valve you can pull the hose off the inlet to the strainer and stick your air horn on it. Give it a couple of honks listening for bubbles under the hull. That usually clears the line.
Throw a couple of bucks at it. Get your hull cleaned and anodes replaced at the same time.
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It sounds like you verified everything is good on the raw water side, except I'm not sure how you verified the mixing elbow isn't choked. I would take it off for inspection.
On the freshwater side, I would question/inspect the freshwater pump, the hoses, the thermostat and the exchanger. When I bought my boat, during the offseason, I pulled everything off that I was comfortable putting back together. I didn't mess around. I just replaced half a BOAT BUCK worth of parts, including all hoses & fuel lines, the 2 pumps, the thermostat, tested the injectors and replaced all the little bits that go inside the chambers. I pulled the heat exchanger completely apart and cleaned it thoroughly (even though it already looked really good). I looked into testing the fuel injection pump, but it looked good and testing it would have been the other half of the BOAT BUCK. It's worth taking good care of the exchanger ... that is a very expensive part.
My attitude when I bought the boat was that everything was 20 years old and I didn't have any history with it. When it's easy to replace parts and not so financially painful, I just go right at it. There is no sense in wondering how good are the old parts. A few of the really expensive parts that are obviously not suspect, I keep. But the water pumps and everything related, including sensers and whatnot - all new. That way, I won't be wondering again for 20 years, maintenance is straightforward, and I get to keep spares.
BTW, have you verified that you are actually overheating with a temperature gun? Perhaps the sensor is off?
thanks, what temp am i looking for with gun? I had alarm go off at full speed plus foam air filter had disappeared.
Basically, the thermostat starts to open at 160 F & fully open at 185 F. You can test your t-stat in pot of water. Normal operating temp is 180 F. I never see more than 165 on my gauge but it's probably because of where the sensor is located. Things to look for: even if the impeller has been replaced recently, there may be parts of a broken impeller vane lodged in the hoses or exchanger if owner hadn't cleared the system after an incident. Also, make sure the hoses aren't collapsing anywhere when the suction increases. I had that happen on my old boat when I used a cheaper automotive hose for a replacement. It seemed to be fine until the system got clogged with weeds. The suction collapsed the hose and then the hose was no good from then on. It was tricky to find ... the hose looked normal while operating at lower speeds. It eventually would collapse at higher rpm, but I always throttled down before looking for signs of trouble. It took a while to realize what was happening. Make sure hoses have the wire reinforcement!
edit for clarification: when I had a collapsed hose, it was with a raw-water cooled engine and the hose that collapsed was the intake between the strainer and the pump. The hose was pretty long because the strainer and thru-hull were on the opposite side of the engine from the pump and the hose had to wrap around the back of the engine to connect on the intake side of the pump. But the concern over a collapsing hose would be the same whether it is on the raw water side or the freshwater side of the system. But you won't find any decreased flow thru the mixing elbow if the hose on the freshwater side is the offending location.
edit for clarification: when I had a collapsed hose, it was with a raw-water cooled engine and the hose that collapsed was the intake between the strainer and the pump. The hose was pretty long because the strainer and thru-hull were on the opposite side of the engine from the pump and the hose had to wrap around the back of the engine to connect on the intake side of the pump. But the concern over a collapsing hose would be the same whether it is on the raw water side or the freshwater side of the system. But you won't find any decreased flow thru the mixing elbow if the hose on the freshwater side is the offending location.
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Are you sure it was in there to begin with? It's not an absolute necessity. Previous owner may have removed it when it was dirty and simply didn't replace it. It will run just fine without it. If that foam had been gobbled up in the air intake, I can't imagine that your engine would even run.
Yes, foam had been there because part of it remained. Didn't seem to do any obvious damage. I have no idea when it happened.
Probably just degraded over the years and was gradually eaten by the engine. I try to check mine periodically but at the end of last season it had lost a big chunk. Our previous boat had a Universal M12 that ate its whole filter sometime in its first 20 years and still ran perfectly well.