SailNet Community banner
  • SailNet is a forum community dedicated to Sailing enthusiasts. Come join the discussion about sailing, modifications, classifieds, troubleshooting, repairs, reviews, maintenance, and more!

Exhaust waterline question?

4K views 27 replies 11 participants last post by  SlowButSteady 
#1 ·
So when I am under way using the 2GM Yanmar on my 1980 C&C MK1 at 2300 rpm's the exhaust port starts to go below the water line? Is this normal? I would think it would be better on top of the water line? Instead of under it..
Any thoughts on this?


I was also wandering if anybody had a like boat and engine that can give me a "SWAG" of the fuel burn? This boat seams to go for ever without burning much fuel. I have been 15 or 16 times out this summer on day sails, with little or no wind sometime and the tank has barely moved. I was Just wandering. I don’t need a hard answer to many variables’ involved for truth. Something close would be close.
Thanks again.
Curtis
 
#2 ·
Some boats, mine included, partially submerge their exhaust port under full power. It is not an issue as long as the exhaust hose has an adequate riser, which it should. On your boat it may be that you are carrying too much weight aft causing her to "squat" under power. I seem to recall a lot of C&Cs have their exhaust ports at the very bottom of their transom.

As for fuel consumption, you can expect to burn somewhere in the neighborhood of 1/2 gal per hour. If you have been motoring as much as you say and your fuel gauge hasn't moved, you might want to confirm that it is working. I don't have the luxury of a gauge so I use a dipstick which leaves no doubt as to how much fuel is onboard!
 
#3 ·
We have the same engine in C & C, power out from winter layup to sail about 9 miles to home port, power half way to race start weekly, power out of channel to do a couple of Sunday races too, same for pleasure sails weekly and then back to layup in October. We topped up $40 diesel in September and another $10 before lift out. We pay $1.43/litre. They sip the fuel, rather than guzzling it.

We also submerge the exhaust when crew of 5-7 is in the cockpit, but the exhaust runs high to the underside of the deck by the transom so we are not concerned. Changed that 25 year old hose and fuel lines this year, sleeping better at night now.
 
#4 ·
OUr 35 MKIII C&C usually runs with the exhaust under water. It does have a water muffler and riser. Our 3GMF Yanmar uses approximently 1/2 gallon per hour at 2700 rpm. Make sure you run your Yanmar at minimum suggested rom...usualkly 3500-2700 to prevent carbong buildup in exhaust elbow.

Dave
 
#5 ·
Normal for exhaust exit to go a couple of inches underwater in the C&C 30-1. The boat "squats" under power. Doesn't hurt anything. As stated above, just make sure you have a loop in the exhaust hose between the waterlift and the exhaust exit. In my boat the exhaust hose loops up high into the transom before going down to the exit point.
 
#6 ·
There is a water muffler and going out of it there is a long hose, newer looking that goes high between the cockpit floor and the transom. So it sounds like it would be plumed correctly and I should not worry if it is gurgling. I did only notice it when we had 5 or 6 in the cockpit and pushing it a bit.
Thanks for the insight,

On the other question RPM's, how would I find out what the Minimum recommendation is for the 2GM 13 hp engine? Would you recommend running it at the top side of that setting to help clean carbon out? Like my Dad use to say he was doing with his old dodge dart?
Thanks again for the help
:eek:
 
#10 ·
Thanks Mark,
That photo was after her bottom job and buffing job back in march of this year, She is a fine looking boat. She sails real nice when you get her in her grove I can almost, just let her go. if she gets too much air she will try to go to weather. Ease her main ever so slightly and she's back in the grove. I didn't quite know what I was getting in for when I got this boat but, I'm beginning to fall in love all over again!!!!
I dont if you sean how bad she was when I found her. tak a look and you can tell she is looking better than she was.
S/V East Coast Lady: Photos of the progress
 
#9 ·
lt....my exhaust is actually undermeath the transome facing down at the water below the boot strip. Oour ransome is a bit smaller and lifted out of the water though.

Dave
 
#11 ·
I rememeber when you got her. Youve done a great job refinishing and bringing her back. Now shes part of the family, yours....and the C&C family. I also have enjoyed reading your progression sailing.

Dave
 
#13 ·
Hey,

One point that has not been made: Make sure that the exhaust flange, where it exits the transom, is properly sealed. On my boat, I have problem where I was ending up with a significant amount of water in the bilge, but only after motoring. I thought it was the stuffing box, it wasn't. I thought I had a raw water intake leak, i didn't. Then I thought that the exhaust was leaking - it wasn't.

The flange that the transom, where the exhaust hose connected to, wasn't sealed. When the transom squatted under power, water was leaking in around the flange. I removed it and properly sealed it. No more water leaks.

Barry
 
#14 ·
Hey,

One point that has not been made: Make sure that the exhaust flange, where it exits the transom, is properly sealed. On my boat, I have problem where I was ending up with a significant amount of water in the bilge, but only after motoring. I thought it was the stuffing box, it wasn't. I thought I had a raw water intake leak, i didn't. Then I thought that the exhaust was leaking - it wasn't.

The flange that the transom, where the exhaust hose connected to, wasn't sealed. When the transom squatted under power, water was leaking in around the flange. I removed it and properly sealed it. No more water leaks.

Barry
I have a very water tight boat. The wet packing leaks maybe 6 or 7 drops a min at adle then a little more while the shaft is spinning. The flange in the back dont seam to be leaking at all.
 
#18 ·
Being new at this, I have made it a habbit of looking over the stern rail looking for the water to be spitting out the back once I fire up the yanmar. It's kind of scarry to wate on an alarm before you know. I dont want to hurt the engine.
Thanks for the help.
 
#19 ·
You're right to do check for water flow every time you start the engine. I suspect that the alarm comment was a bit of sarcasm. Most A4s don't have alarms installed, although they're a good idea as they'll also warn you about low oil pressure. The most common mistake I make when starting (always while sailing, not leaving the dock) is to leave the choke closed. After a few minutes I notice the engine is running very rough. It then takes a while to burn the fouling off once I open the choke. I need to install some kind of "choke alarm."
I noticed you said that your stuffing box leaks at idle. Is this all the time, even when the engine is off? If so, the packing nut probably needs to be tightened a little bit. The short version is, it should not leak when the shaft is not turning but should drip a little when the shaft is turning. If the packing nut is too loose, it will leak at idle. If it's too tight, it will overheat and the packing may be so tight that it scores the prop shaft, making it impossible to get a good seal in the future.
 
#20 ·
Well it drips with the engine running in netrual maybe 5 or 7 drops a min. Cant tell when in gear but its not too much. Should it be tighten up?
My engain is a 2gm Yanmar 13 hp. it has no choke on it. It starts up with the greatest of ease. No-choking a diesel right? Here is the packing I just had it repacked at Marsh harbor boat works.


 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top