Diesel Woes

[frank balcer]

Down to the boat last night for some cleaning for an upcoming trip in a few weeks and decided to run the engine for a bit as I have not cranked it in about 4 weeks. Cranked right up but imediately noticed NO water coming out of exhaust port on the stern. Shut it down rechecked seacock and restarted with same results. Blocked in seacock and checked line from it to strainer(clear) pulled raw water pump apart and replaced impeller (old one looked good, no missing pieces or deformity) checked line from raw water pump to heat exchanger(clear) pulled heat exchanger ends (tubes clear)
I'm guessing the only thing left to check is the mixing elbow. Seemed to be running fine 4 weeks ago. My question is could this elbow get clogged in just 4 weeks of non use?
And 4 weeks ago i only ran long enough to get from hurricane tie out point back 50 yards to slip. I am hoping to go down this evening after work and try to removed the mixing elbow to look see. Any ideas anybody???? Thanks in advance....frank

 

[kloudie1]

Pull the sea water line off the strainer .. open the seacock and make sure you have a good flow of water .. Your strainer fitting under the hull may be plugged and not allowing water in..If no flow, use a dockside water hose to pressure backwards from the seawater strainer inlet hose out.. don't pressure the engine with water from the dockside hose.
When you are sure you have water at the pump inlet, briefly remove the engine block inlet hose (with engine idling) from the pump to make sure the pump is pumping. VERY briefly because the exhaust is not being cooled if no water is flowing.. If pump pumping but no water out back of boat, then elbow and fittings.. Good luck with finding that potato chip bag on the inlet..

 

[frank balcer]

Thanks Kloudie, pulled line off last night and had a good flow of water when seacock was opened. Only thing left that I can think of is the mixing elbow. Hope I can get it off without destroying it!

 

[kloudie1]

Good luck with it, Frank.. Figured you'd checked inlet but just wanted to make sure..
Beautiful weather this morning .. Going to boat today for a couple of days !

 

[Scott T-Bird]

Don't rule out the impeller ... every single time that I have changed out a failed impeller, I have never been able to see anything wrong with it. It's a mystery to me why they fail when there is no discernable difference between a failed one and a brand new one, but that's been my experience in changing about 6 or 7 of them in 9 seasons.

It's odd to me especially because in 25 years of owning a ski boat with an inboard, I have never had an impeller failure other than for an odd circumstance where the intake was plugged with sediment and the impeller had obviously disintegrated.

You can pull the hose off the outlet side of the pump and run it briefly to see if the pump is working. If not, it is likely the impeller.

 

[hutch5151]

Check the anti-siphon valve on the intake hose. If it sticks open you will have a air leak and this will reduce water flow. You can also check the mixing elbow for blockage by pulling the small water tube that leads from the back of the cyl head into the side of the mixing valve. If this inlet is fouled, then you will probably need to replace the mixing valve. If this is a raw water engine, mine is, than you also need to look into the rear of the head for salt build up and blockage. Call me if you have any questions 850-543-3741 I pulled my head and had it rebuilt shortly after buying my Elite 37.

 

[capejt]

What I've found

Don't rule out the impeller ... every single time that I have changed out a failed impeller, I have never been able to see anything wrong with it. It's a mystery to me why they fail when there is no discernable difference between a failed one and a brand new one, but that's been my experience in changing about 6 or 7 of them in 9 seasons.

It's odd to me especially because in 25 years of owning a ski boat with an inboard, I have never had an impeller failure other than for an odd circumstance where the intake was plugged with sediment and the impeller had obviously disintegrated.

You can pull the hose off the outlet side of the pump and run it briefly to see if the pump is working. If not, it is likely the impeller.

I too have replaced the impeller in the past for "no apparent reason" only to find that although the vanes and entire impeller appeared to be intact on the "bad" one, the center (not sure what to call it) was able to turn without turning the whole impeller. This could be the problem

 

[Scott T-Bird]

Yeah, the little metal hub ... I suspect that it separates from the rubber and you would never see it. I changed my water pump last winter and was hoping to see that impellers would last longer. I'll probably never know because I plan to re-power this winter ...

 

[Deadline]

Two things

1. Impeller may be fine but you may be leaking air through the cover, forming cavitation. Virtually indiscerable without even a water leak (because water isn't drawing actually). This arises if you use both a paper gasket and a goopy gasket. Use one or the other, not both. Took my Yanmar mechanic four hours to deduce the problem. Once corrected, never again.

2. Sitting idle didn't necessarily block the mixing elbow. It just happens. If it's a 2GM20 you dismantle at the manifold and then take the two pieces apart. Replacement elbow is $150 while acid cleaning it is $40. Mine coked up within 350 hours even though I ran it at optimum RPM. The culprit was those low RPMs exiting and entering slip a total of 100 times a year times 3.5 years. Who knew.

 

[Stu Jackson]

Good point about the faceplate. Also, if it's not smooth inside, the impeller may not work even if it's perfectly new and good. Either sand the faceplate to remove grooves or buy a new one and a new gasket.

 

[sailaway78]

Another possibility

I once had a similar problem, and found that the cap on the raw water strainer was loose, which allowed it to suck air. It doesn't take much to keep the pump from priming when the system has been opened. Good luck on finding the problem.

 

[rardiH36]

Good point about the faceplate. Also, if it's not smooth inside, the impeller may not work even if it's perfectly new and good. Either sand the faceplate to remove grooves or buy a new one and a new gasket.

As another alternative, a Yanmar distributor once suggested just reverse the pump faceplate so that the outside is now inside. This worked on my Yanmar 2QM20 engine impeller pump. But of course the faceplate screw holes need to be mirror image so they line up when reversed (mine were). And of course if the outside of the faceplate has been painted, then that has to be removed. Placing the plate in acetone or lacquer thinner for a while will do it without the need for sanding/scraping.

 

[Rob2435]

If the impeller is belt driven check that the belt is turning the impeller. I did this by marking the impeller pulley with a sharpie and and a friend turn the engine over...the belt wasn't tight enough to turn the new impeller.

 

[frank balcer]

FOUND IT! Mixing elbow was totally blocked! And previous owner installed it in May of 2008, date was still legible when he put it on. Now to take it to work for a visit with the glass bead blast cabinet.....Thanks all!

 

[seadaddler]

Cleaning

I have cleaned out mixing elbo's on 2 yanmars and tried getting it cleaned out at a radiator shop and was told boiling or other blasting or acid will not work.
I took the 2 pieces apart and cleaned it with all ice pick type of tools like a pointed chisel too and hitting with a hammer too,it took time but the hardnish of the clogged did take work with the pointed tool.
I am not saying it did not clean out the hole passage just that you will need to work it with good pointed tools and watch the very hard coking come out like bread crumbs not very big chunks,after a hour or 2 of work I did soak in a acid,like I said trying to get a good passage opening again.
The hard part getting the 2 pieces apart and had to take to marine repair shop for $20 to take apart.:dance:
Good Luck
Nick

 

[frank balcer]

Glad bead blasting work pretty good. Will try it tonight after work!

 

[Granfalloon]

Consider - getting a new mixing elbow, clean the old as a backup; run the engine at no less than 80% of max RPM the majority of the time. A 5 minute high RPM run after the engine is warmed up. I do this on the last leg returning to the slip. And a 30 second run up in neutral just before shutdown.

 

[Anonymous 121765]

Frank,

I do know from friends over the years that not all mixing tees are equal. I believe most who had clogging problems, had the same brand. I believe it was a Yanmar 180° fitting that acted as both mixing tee & anti siphon. (but don't quote me on the manuf.) . It had opposing baffles and by this poor-thought design was destined to clog. Just a bad engineering design decision for a diesel (soot type) system.

I had fabricated a mixing tee right before the muffler inlet. There are no baffles in this and I oversized the water mix inlet fitting but, with no baffles and the larger water feed it works great. The hose is sized up just before the connection.

Let us know what make mixing ell you have pal.

CR