Yanmar seawater exhaust bleeder plug

[maury]

This photo shows the few inches of lift if I installed a 90 elbow into the vetus. Significant improvement but not a downward drop. What do you think.

[maury]

Ok, I got all kinds of good answers. Just had a call back from the Yanmar distributor who fields theses calls for Yanmar.

1. Bleeder Plug: Mine seems to be defective in that occasionally I grt a couple of cups of water coming from there into drip pan so I will replace it with a petcock from yanmar dealer

2. Hose to exhaust elbow I will route high with a siphon break.

3. It is ok to install an extension elbow made for yanmar sold by HDI Marine on ebay 7” or 9” stainless steel.

4. Hose as mentioned should be 50mm or 2” not the 1 9/16 installed which will cause a back pressure problem. This leads to the issue of an undersized Vetus I have the 40 size and should have the 50 size. Exhaust from there should also be 50 mm, 2” with a downward slope after the top of the lift.

[maury]

I should add, I had been wondering how a 2” or 50 mm hose would connect to the exhaust elbow since any connector would narrow it. Ends up hose goes over the end of the untextured round out area of the exhaust elbow.

Ends up the extensions are available 5-9” long for $44-66. Premade wool covers are about half of that price and it gets hot so it should be covered.

[maury]

I want to thank everyone who shared a lot of answers which helped me develop my understanding of the whole picture. It was quite challenging and now I am needing to prioritize given funds are at the bottom.

I’m thinking first thing is to focus on potential back flow issues by 1) adding a 7 or 9” riser to increase height of exhaust elbow. I will also 2) add a longer hose and anti siphon loop to hose from heat exchanger to exhaust elbow. 3) hose going to transom of the boat will be rerouted to begin a downward slope once it reaches its peak.

Somewhere along the way I will get a peecock if engine draining increases when I run it longer.

The second big issue has to do with exhaust system pressure. While I feel this may be important in the bigger scheme of things based on conversations here I feel it is not an immediate necessity so can be handled with time. Resizing hoses, Vitus and I assume boat exhaust all needs to happen at once so this may take some time.

[SY Harmony]

Originally Posted by maury

This photo shows the few inches of lift if I installed a 90 elbow into the vetus. Significant improvement but not a downward drop. What do you think.

I’d flip it and run it.
The difference in replacing the exhaust system, vs life lost on the engine is an impossible number to quantify without specific testing. Will the added back pressure take 10, 100, or 1000hrs off of the life? Who knows....
How much does back pressure change with carbon build up in the elbow?

There comes a point with ALL boats where you have to say “that’s good enough”. Exhaust system integrity and prevention of back flow IMHO is a greater priority than a minor increase in back pressure.

[Dalestr]

Your boat was built with an engine with stbd side exhaust. Your YM engine has port side exhaust. At shutdown, the water lift muffler is essentially a reservoir that collects the water coming back from the exhaust hose, the exhaust elbow, and also the elevated siphon break. When your boat is sailing on stbd tack and heels 70 degrees in a big gust, where does the water go?
That’s why we want to keep the whole exhaust system parallel with the ships centerline — within reason. So, I’d like to see at least your muffler moved to port side or even close to the centerline and most of rear hose too. It doesn’t need to be a solid mounting BTW. It could float on lines or bungees supported largely by the hose.
The anti-siphon is an easy fix for you. Getting geometry of exhaust system right is the tougher problem.

No way you need or want 2” hose for this engine. The Yanmar U mixer/riser is used on many Yanmar engines over the years, even a 34hp (3HM35) model, and while 2” hose is used for bigger engines, using the internal threads of the mixer for a SS hose tail is best for smaller engines. Those threads are 1.25” BSPT. 2” hose is also much stiffer and awkward and it will contain more water to flow back at shutdown due to slower velocity. My friend’s Catalina 320 has a 29hp engine and uses a quite long 40mm (1-5/8”) hose. Greater back pressure is created by the sharp 90 degree elbow in their custom muffler than from this hose.
I do worry some about extending height of your mixing elbow higher than needed as these engines do shake. If extending more than 5” you might consider adding a brace. My 2GM20F has a cast iron manifold to take the stress and I hope the YM does too.

[maury]

@Dalestr keeping mixing elbow extension to 5” I think is doable and what I have been seeing as best for having a downwards flow with no upwards. The manifold is cast iron. As for adding a support would that be a galvanized strapping to nearest wall?

I will run the insulated hose from heat exchanger to exhaust elbow on port into the side of quarter birth so at least keep this on the same side

Rerouting exhaust past exhaust elbow is to start the drop immediately instead of loop to vetus and then after peak of gunnel loop followed by a drop. To switch it to the quarter birth on port would not be a good idea for many reasons including the exhaust outlet is not movable without excessive expense.

[skipperpete]

Originally Posted by maury

@Dalestr keeping mixing elbow extension to 5” I think is doable and what I have been seeing as best for having a downwards flow with no upwards. The manifold is cast iron. As for adding a support would that be a galvanized strapping to nearest wall?

I will run the insulated hose from heat exchanger to exhaust elbow on port into the side of quarter birth so at least keep this on the same side

Rerouting exhaust past exhaust elbow is to start the drop immediately instead of loop to vetus and then after peak of gunnel loop followed by a drop. To switch it to the quarter birth on port would not be a good idea for many reasons including the exhaust outlet is not movable without excessive expense.

If you choose the option of extending the mixer elbow vertically, the support bracing can’t go to “the wall”, it usually attaches to either the flywheel housing or gearbox and occasionally to the engine lifting bracket mounting point if the geometry permits. Extending the elbow is not an option I’d choose but it will solve the backflooding risk provided you still install a decent vent loop. Without the vent loop its still able to siphon the water until the Aqualock fills to the WL.... just not over the top of the hill and into the engine,....... and if she does fill the Aqualock to that extent I suspect that the backpressure would be enough to prevent the engine from starting.

[maury]

@skipperpete Vent loop with quality vent to exhaust elbow is the easiest fix.

Down hill to Vetus pretty much only has one realistic doable option, the 5 inch extension which I can see actually happening. Other approaches are to resource and project intensive at this time. In your opinion is it better to not add 5 inch extension and leave the present loop as is?

[skipperpete]

The extension and the siphon break solves both of the current deficiencies but not in an elegant and enduring way, it won’t be inexpensive modifying that heavy chunk of cast iron and bracing it so it doesnt damage the heat exchanger in the future.
If I was the guy hooking up that exhaust, I’d put a silicone hump hose or joiner off the OD of the mixer straight into the aqualift after you move it to the opposite side from where it is in the original photo.
Anything other than what you have in that photo will work as long as you fit a siphon break FIRST.
You’ve come a long way from the heat exchanger drain fitting to saving that lovely little engine from infant mortality and now have a really good understanding of the function and dangers of a wet exhaust, really good work on your behalf for asking all the right questions and correcting the problems.

[maury]

I added a 7” lift to exhaust elbow and finally have a mostly downhill to vetus now. Overall the hose is lower then exhaust elbow and I can wire the high spot down lower for a complete slope. Unfortunately there is now a kink in it but I have a spare if needed so can replace it. Given the backwards flow issue is mostly resolved do I still need a 90 degree for vetus. Turning the Vetus 180 degrees as some have recommended is not a workable idea for several reasons. I have a long hose now lifting the water pre-elbow and now have funds to purchase the vented loop this week. I saw a stainless 316 loop for a head, I can assume that would work.

A new issue arose when doing a shakedown sail. The engine in forward will only rev at 3000 rpm yet in reverse about 3600. In neutral it goes higher. I studied all linkage movements and nothing seems off with forward and reverse having the same range. The only subtle difference is in reverse at transmission linkage when reving higher in reverse it seems like at one point it shifts ⅛ or ¼” additional. Is there something about this point I need to know or adjust for?

[Icarus]

Originally Posted by maury

I added a 7” lift to exhaust elbow and finally have a mostly downhill to vetus now. Overall the hose is lower then exhaust elbow and I can wire the high spot down lower for a complete slope. Unfortunately there is now a kink in it but I have a spare if needed so can replace it. Given the backwards flow issue is mostly resolved do I still need a 90 degree for vetus. Turning the Vetus 180 degrees as some have recommended is not a workable idea for several reasons. I have a long hose now lifting the water pre-elbow and now have funds to purchase the vented loop this week. I saw a stainless 316 loop for a head, I can assume that would work.

A new issue arose when doing a shakedown sail. The engine in forward will only rev at 3000 rpm yet in reverse about 3600. In neutral it goes higher. I studied all linkage movements and nothing seems off with forward and reverse having the same range. The only subtle difference is in reverse at transmission linkage when reving higher in reverse it seems like at one point it shifts ⅛ or ¼” additional. Is there something about this point I need to know or adjust for?

Sounds like the the clutch is slipping in the fwd position.
Take the clutch cable off the selector lever and check the distance the small lever travels fwd and aft position.
Check how far the cable can move either way with the throttle lever pushed fwd and aft position.
Adjust the throttle cable so it can move the throttle lever fully either way.
If that doesn't work the clutch is worn and needs adjusting or replacing.
Check the colour of the gearbox oil it it's black might indicate a slipping clutch.
Chech if you have the correct type of gearbox oil.. Some boxes need ATF and do not overfill.
I had a similar problem on my Twin Disc gearbox which has a cone clutch... I had to adjust the selector and found the gear box oil was overfilled.
Hope that helps

[maury]

Originally Posted by Icarus

Sounds like the the clutch is slipping in the fwd position.
Take the clutch cable off the selector lever and check the distance the small lever travels fwd and aft position.
Check how far the cable can move either way with the throttle lever pushed fwd and aft position.
Adjust the throttle cable so it can move the throttle lever fully either way.
If that doesn't work the clutch is worn and needs adjusting or replacing.
Check the colour of the gearbox oil it it's black might indicate a slipping clutch.
Chech if you have the correct type of gearbox oil.. Some boxes need ATF and do not overfill.
I had a similar problem on my Twin Disc gearbox which has a cone clutch... I had to adjust the selector and found the gear box oil was overfilled.
Hope that helps

I know they mechanic I hired prelaunch to test the engine did overfill it. Tomorrow I will try to figure out how to remove some. After another test I will go the measurement method you mention. Engine is brand new has 6 hours but installed years ago post 2005.

[skipperpete]

Hi again Maury, there’s a large difference between the reduction ratio in ahead and astern , all the KM2P-1 reversing gears are about 3:1 reduction in astern but there are 3 different available ratios in ahead, it sounds like the boat is overpropped but only in ahead, the 3:1 reduction in astern is more suited to the propeller. What type of propeller do you have? Fixed , folding or feathering? I appreciate how much effort you put into the exhaust system and its way better than the original installation but still could be improved, the weight of that mixer and swan neck should be additionally supported by a decent strut to either the bell housing bolts or the lifting eye bolt to take a bit of the load off the end of the heat exchanger.

[Dalestr]

The difference in RPM may be due the different gear ratios, Fwd vs. Rev. as Rev is normally lower.
But do verify the min. travel of the tranny actuator arm is achieved per Yanmar spec.
Your prop is a bit too much load for this engine/gear/boat combo but you're still breaking in a "new" engine. If still only 3000-3100rpm after 10 hrs running, you could change prop down 1" dia. or pitch but run the numbers using online calculator -- for existing prop first. You may want 3600 rpm available in smooth water condition to optimize your power. Keep engine room temps under control with power ventilation.