Mixing Elbow

[Rick D]

So, I have 2100 hours on my 4JHE in my 1994. But, I have never replaced nor cleaned the exhaust elbow other than running a gallon of vinegar through the system every year.. The 3GM in my 32 Vision tended to be troublesome and it was cleaned annually. So, I am wondering if any of you guys with the 4JHE have had any issues with the elbow. I know the Catalina 42's run the same engine but they have made-up elbows.

 

[Steve Dion]

Rick:

I am curious about your vinegar treatment. Do you just open the strainer and pour in the vinegar while the engine is running? Could you tell if it was actually cleaning anything out of the system.

We did something similar to one of the Hunter 30's in the harbor with one of the old single cylinder engines and a bunch of rust and crap came out of exhaust. We used oxalic acid.

 

[Rick D]

Vineger

I have used acid twice, but the vinegar is obviously less corrosive. I just close the intake through hull and pour a gallon into the strainer. I let it sit for a couple of minutes and then start it up. You can see some deposits coming out so something is happening. I do it annually when I service the engine.

 

[seadaddler]

Flushing

Do you let the vinegar run into the engine than shut it down than let sit inside the heat exchange for ? and than atart the engine and flush with more inegar,that's what one of my dock neighbors recommends and has even done this with salt away.
Does this sound OK or what.
Nick

 

[Don12364]

My 3JH2E is now 15 years old with about 1500 running hours and is of the same configuration as the 4JH engine - only 3 pots instead of 4.
Because of the many postings on this site I have had it apart twice, second time stripping one of the studs in the heat exchanger because I did not realise it was aluminium.

On each occasion there was very little build up of carbon or limescale so I have not touched it these last six years.
What I did notice was that the little weir inside the elbow was almost rusted away.
This could result in water getting back into the exhaust manifold and hence valves and even pistons.
Anybody else noticed this potential problem?

 

[Rick D]

Re: Flushing

Yup. That's what a power boater taught me. I let it sit for a 'couple' of minutes in the heat exchanger.

 

[Don S/V ILLusion]

Can't attest to this with personal experience as I've never disassembled mine to verify but this is what Yanmar Tech Services told me: apparently there are two types of elbows used on the 4JH, one composed of cast and one alloy. The latter, I was told, should be fine for it's useful lifetime while the former does experience some buildup which requires periodic cleaning. He explained that because of the composition, one maintained a more ideal temp to preclude buildup. As mine is the alloy ( distinct appearance from the other but I don't have a picture), I never bothered to inspect so my advice if you are really interested is to talk directly with Yanmar for the most reliable answer.

 

[Steve Dion]

Rick:

....and you know those stink potters know a lot about engine maintenance. It becomes a way of life for those guys.

 

[Vinny]

apparently there are two types of elbows used on the 4JH, one composed of cast and one alloy. The latter, I was told, should be fine for it's useful lifetime while the former does experience some buildup which requires periodic cleaning. He explained that because of the composition, one maintained a more ideal temp to preclude buildup. As mine is the alloy ( distinct appearance from the other but I don't have a picture), I never bothered to inspect so my advice if you are really interested is to talk directly with Yanmar for the most reliable answer.

This has been discussed before here. The 4JHE as designed by Yanmar has the Alloy mixing elbow. Now comes boat builders like Hunter (and others as well) and they are going to fit 5 lb of stuff into a 4.5 lb bag. Like on the H40 Legend series. The original elbow makes the exhaust not fit in the dog house. It is to big (both in diameter and length) so what is a body to do? Mack Boring fits the 3GM mixing elbow on the engine (cast iron and smaller bore) and Hunter shoehorns the thing into the dog house. This causes a slight loss of HP (exhaust size reduction) and in addition if not run up at 2,700 - 2,800 rpm the elbow carbons up more than the Stainless smooth original mixing elbow.

Bottom line is they will carbon up if not run up and they will deteriorate (cast iron and salt water). Your mileage will vary depending on how you run your engine. But not running the engine up is harmful to your engine (or any Diesel for that matter) in more ways than just the mixing elbow. But that is another discussion.

Oh BTW your Yanmar person for the most part doesn't know this (the reason for the difference in mixing elbows). It took me three weeks with calls to Hunter, Torresen Marine and Mack Boring in NJ to track this down. Boring made the modification for Hunter with Yanmars approval.