Question for all gearheads

[petersea]

Orion253
"1) The red marine fuel makes my engine knock or backfire..... don't know which, but it sounds like a gun going off under water and hitting the boat making a kind of muffled pinging sound. I guess the red fuel has either a little lower or higher octane rating. This makes the fuel harder to burn so it fires early or late. If I were to put regular road diesel in the tank I think it would stop......... Yah ahhhhhh....... it might fix the problem....... to bad I can't try it because that would not be legal. Do you use Marine Diesel ??? "


Diesel fuel is diesel fuel the only difference between off road and on road diesel is the tax and a redish dye to indicate that tax has not been paid. When they "make " off road fuel all the do is add dye to the tank truck delivering it. It is very much like a food color. If you are having a performance issue using off road diesel vs road diesel there is something else going on, maybe try a different supplier with a lager sales volume to get a fresher supply or maybe your retailer has a tank problem. As others have said there is no legal issue using road fuel in a off road application. Same thing as buying gas from a gas station (you also pay road tax) for your (off road) lawn mower. So go ahead and put the "road" fuel in you boat besides the federal and state government will alway be glad to accept you tax dollars when you by the road fuel !


P.S. to Orion 253

Diesel does not have a "octane" rating per say.(diesel does have a octane rating but it is not real world applicable) Diesel combustion rating is called cetane similar but not quite the same thing check out

linkhttp://alternativefuels.about.com/od/researchdevelopment/a/cetane.htm


"Similar to the octane number rating that is applied to gasoline to rate its ignition stability, cetane number is the rating assigned to diesel fuel to rate its combustion quality. While gasoline's octane number signifies its ability to resist auto-ignition (also referred to as pre-ignition, knocking, pinging, or detonation), diesel's cetane number is a measure of the fuel's delay of ignition time (the amount of time between the injection of fuel into the combustion chamber and the actual start of combustion of the fuel charge).
Because diesels rely on compression ignition (no spark), the fuel must be able to auto-ignite--and generally, the quicker the better. A higher cetane number means a shorter ignition delay time and more complete combustion of the fuel charge in the combustion chamber. This, of course, translates into a smoother running, better performing engine with more power and fewer harmful emissions."

 

[sailaway78]

Orion I think maybe

I think maybe you have an injector pump a tad out of time. Sounds more reasonable than any fuel difference.

 

[Cayennita]

If you are motoring and heeling 35-40 degrees, it is possible that the intake was sucking air. The water muffler empties and fills, etc. You mentioned that it made noise as if it was a dry exhaust. Then it is possible that you were getting water hammer similar to an old home heating radiator.

 

[sailaway78]

Nope

Raw water intake is on the port side, and I was heeled over to port. So the raw water intake was buried.

 

[Cayennita]

Also make sure that all the coupling bolts are there and tight. If only one is left, imagine the racket.

 

[Maine Sail]

My vote is shaft slap of the shaft log... Boat heels, shaft is not already perfectly centered in the stern tube, motor moves a bit on the mounts and the shaft begins banging the shaft log tube. Pretty common actually...

 

[Butch23065]

Transmission noise...

We had a 34' Pearson with a 3 cylinder Yanmar and a Yanmar transmission. The sea trials and survey all went well. It was fall, the boat was pulled and shipped to our marina. Come spring after the launch, any time I would go close to 2000 RPM it sounded like the engine was going to brak loose from its mounts. Ocassionaly if we ran full throttle it would smooth out. I fought this for 6 or 7 years until a parts man at my local Yanmar service shop gave me the answer. The transmission was a cone drive and if the linkage is just a little off it allows the cone to let go and grab again. It is a banging or as you described a machine gun noise. Sometimes under a heavy load, full throttle it puts enough pressure on the output shaft to stop it from slipping. If the load is light, 1500 RPM or less there is not enough resistance to cause ot to slip. I replace the cone drive gear and never had another problem.

 

[Anonymous 121765]

N&E,

I have a phrase I use for these unexplainable mishaps pal. I call it "FM", the second word being magic.

I would like to know if you go under to inspect, I would look for scratch marks, netting, line or goughes in your bottom paint. I dunno about the shaft & log interference as if this did happen, I would bet there was visual evidence at the cutless bearing. Look at this to see if your rubber insert moved somewhat or out in this condition, this could explain what you experienced as a whipping noise insync with the RPM's.

It is possible your engine alignment came off center, or the torque under these conditions twisted the alignment. Do you recall the RPM's when the noise occured?
I recently changed my engine mounts as the rubber (gummys as Stu calls them) finally became weak. Under intense, load these are not working.

CR

CR

 

[J Hunter]

A bit off topic but I read the post about having diesel with too high an octane rating (not usually discussed like that, but no reason not to I guess) and the other post giving a fairly accurate description of the two ratings and I just would like to share my understanding of it that I remember from diesel school which some might find a bit simpler:

Octane rating or number: It is a measure of a fuel's ability to resist compression ignition. Compression ignition in spark ignited engines is unwanted, so the ability to resist it is the quality that gets a higher rating. Pure octane is the standard and is assigned a rating of 100. Spark ignited engine fuels that resist compression ignition more than pure octane are rated over 100 proportionally and fuels that resist compression ignition less than pure octane are rated lower than 100.

Cetane rating or number: This is similar but opposite. It is a rating of how little resistance to compression ignition "diesel" engine fuels have, usually referred to as their "ignition delay." In diesels, long ignition delays are unwanted so the shorter the delay the higher the rating. Pure cetane is the standard and is assigned a cetane rating of 100. Fuels that are even faster to compression ignite than pure cetane (are there any?) would be rated more than 100, and vice versa proportionally to pure cetane.

Experts feel free to correct my memory as necessary.

Note: although cetane and octane rating explanations number in the millions on google, no one it seems has tested and electronically published the cetane number of octane, or the octane number of cetane. God, I'm weird.

 

[Anonymous 121765]

J,

Your not weird pal, you a sailboater & like all of us seek answers. No one likes grey spots in their mental toolbox of knowledge. I just think the fuel companies don't want us to know or they don't feel the need. I'm sure they have tested results.......

CR

 

[forever faithful]

AK47=water pump?

Here's the situation. I was heading into Biloxi, in the east channel. It is only a little over a mile long, and fairly narrow. Skinny water on both sides. I have a thunderstorm pounding me pretty good. 30+ knots and a very nasty following sea. About half way up the channel, the wind shifts, and picks up. Gusts approaching 60 knots, dead on the beam. The boat is pitching with the following seas, and heeling over 35 or 40 degrees to port. Wallowing real bad. I'm managing pretty good, but it's work. All of a sudden something goes off, sounds like a AK47, on full auto. Very loud. And sounds like it's coming from under the boat. My mind is trying to solve two problems at once. What is wrong, and what am I going to do if something breaks. There is no way I can get anything done in this channel before I get blown out of it, and find the bottom. I throttled back to about 1500, the frequency of the noise reduced as the RPM came down, but was just as loud. Then after a lifetime, it just faded away. Real time less than a minute. About 20 minutes later the exact same thing. Again after less than a minute it faded away. And before I got in, one more time. As soon as I got behind Deer Island, into calmer water, it was gone for good. I checked everything I could think of. Oil pressure was a steady 55lbs, water temp @ 135. I thought maybe something had shaken loose and was hitting the coupler. NADA. Today I took her out and played around in some fairly snotty conditions, but could not make it repeat, but I couldn't duplicate the conditions. I can find absolutely nothing wrong, anywhere. Any of you gearheads have any ideas. I have a theory floating around in my heat, but am going to wait and see if anyong else has the same idea.

My 1983 h34 has made a clicking sound right from our pre-buy sea trial last November. With the boat hauled and hung, inspected bottom and found it to be pristine including shaft, cutlass and prop. Installed new zincs. Over these last months, the clicking sound has slowly worsened. It would occur in neutral, shaft not turning. In both neutral and underway, the clicking frequency would vary with the throttle adjustment. At the higher rpm, the sound became much less. Lifting the motor hatch, there would be no apparent sound from the engine bay. The sound definitely seemed to emanate from the transom area of the boat.

Well, yesterday, we decided to go out for a sail. Started the engine to warm up while we prepared. Noise was decidedly louder. I opened the engine hatch and felt a spray of water on my face. Shut down the engine and quickly found the source of the water spray. I could pull the pulley of the water pump forward and back about a good half inch with a subsequent increase in the leak. The water pump is off and I am picking up the new one on Thursday.

Barbara, my partner, suggests that the noise of the water pump was transferred down through the engine and shaft to the stern of the boat where the transom chamber amplified the noise to an audible level.

She's very sharp and I agree with her. The proof will come at the end of this week when I install the new pump and start the engine. Fingers crossed. Will let you know the outcome. In the meantime, check that water pump!

 

[jviss]

Test it

You can test your theory about the water muffler burping out all the water by simply draining the muffler and starting the engine. The muffler is almost certain to have a drain cock on it (mine does).

 

[sailaway78]

Noise

OK Took boat home from Gulfport Thursday night. 9 hours of motoring, as there was no wind. Ran her at 2600, which seems to be the sweet spot, all the way home. Not one single thing amiss. No noise, no vibration, no RPM fluctuation, no increase in temp, not fluctuation in oil pressure. In other words, everything was perfect.
And I may drain the water muffler and check that out as suggested. While I believe that whatever that noise was, it was something akin to an anamoly, I still would like to know what. Will get under there in the next few days and take a look.
By the way, the cutlass bearing was new two years ago, and there is less than 150 hours on it since.

 

[healeyman]

Hey Nice and Easy.... so glad your engine is normal... you may never know what caused this. On the upside... look at all the good conversation and advise you created... shows how willing sailors are to offer help and suggestions and we all leaned from these posts. So, thanks again for sharing and good sailing .

Dave

 

[sailaway78]

Under the boat

Finally managed to get under the boat and have a look around. Everything looks as it should. Zincs in place, no movement in cutlass bearing. Not a scratch on the bottom, anywhere near the prop. So, I guess will never know for sure. Hopefully will never be in those same circumstances again. This has been an interesting discussion, and I do appreciate all the idea given. There is no drain on the muffler, so can't check that, but am just going to consider this an anomoly and go on sailing the boat.

 

[forever faithful]

Re: Under the boat

Oh, no! AK-47 does not = water pump! I replaced the water pump and did a trial run of my 1983 H34 hoping the clatter sound had disappeared. No luck.

I now think that I need to squeeze down into the transom space via the starboard cockpit bench access. I need to convince myself that something isn't in that area rattling whether the engine is running in neutral or in gear.

I will continue my quest while I celebrate Nice N Easy's success in having the noise leave on its own.

 

[Anonymous 121765]

N&E,


Keep in mind that mechanical problems will never fix themselves.
I believe aside of some netting or line fouling your prop, the problem can only be one of the following.

Engine alignment, motor mounts, worn cutlass, loose or rattling piping, belts, alternator mounting, internal engine problem, or what hasn't been addressed as of yet, a linkeage/shifter problem.

My controls are down low & sometimes an errant foot can partially disengage the tranny linkage. Or under those extreme circumstances, partially disengaged gear can sound as what you had described.

Do a thorough check on the latter. have someone shift gears while you check on the trans shifter arm & check the cable adjustment sets.

Just my input pal....

CR

 

[jviss]

Mechanical problems don't fix themselves; this might not be a mechanical problem. I think the most likely source of the noise is that the muffler went dry.

 

[healeyman]

gremlins! those pesky gremlins.