Vibration Under Power, is it normal?

[Will Baker]

This season, prior to launching my boat, I had the propeller shaft aligned. I have only had the boat out a few times-I've only owned her a short while. Anyway, I notice that when she is under power (yanmar diesel running, sails down) there is some vibration associated with the running of the engine. It happens only at a certain RPM, if I go lower or higher than the vibration point it stops. When the vibration is occurring I can feel it in the tiller, and the life-lines actually shake.This past week, I ran aground on some rocks. I was under power at the time, and was going very slow (less than two knots). I had a passing power-boat pull me off. The impact was not severe, and I believe that, other than scraping the bottom of the keel, no damage resulted. I did not hit the rudder, hull, or propeller, I just scraped the keel.I am not sure if the vibration I described above was present before I ran aground. My question is, is this vibration normal? I was with the mechanic when he was aligning the propeller shaft, and in response to my question about engine operation/idling, he indicated that these single cylinder diesel engines do vibrate, and some folks adjust the throttle to minimize the vibration.Of course I would prefer that I did not run aground. And I am wondering how badly I screwed up. Do folks I need to have the shaft re-aligned, or is this vibration normal? Again, I was going VERY slowly when I ran aground, and it felt like only the very bottom of the keel stuck in the rocks. If anyone has advice I'd appreciate it-I'm loosing sleep over this

 

[Steve Dion]

Vibrations are not uncommon.

Will:Vibrations are not uncommon. This is especially true with a 2 blade prop. If you get vibs at specific RPM's, then you should just increase the throttle a little.Did the shop that aligned the engine check the prop balance?

 

[Will Baker]

Thanks for putting my mind at ease

Steve,Thanks a bunch for the reply. I do not believe that they balanced the prop. I suppose I should maybe have that done after I haul her out at the end of the season and before I launch next year. Hey, I used to live in Rio Vista in the early eighties. I worked for a company called Dutra Construction and then Blackwelders. I rented a place at the Spindrift Marina right on the river.I was concerned that I might have thrown the shaft out of alignment when I ran aground, but again, I was going so slow (two knots or less) and it sounded/felt like only the keel scraped on rocks, that I couldn't imaging that I did any harm (other than having to repaint the bottom next year, and I was planning on doing that anyway). Based on my description of the grounding incident, do you think I harmed anything?My depth sounder wasn't working properly that day and I have since found and corrected the problem-the wire connector in the engine compartment that supplies voltage to the lights and accessories panel came loose.Thanks again for getting back to me. Will

 

[Michael O']

Good/Bad Vibrations

I have chatted with other Hunter owners who report vibrations under power. Many report increased vibrations when turning to port. Some also have discovered vibrations that change going over waves while at a constant rpm.I've checked my engine alignment and replaced the cutlass bearing. I have the Gori folding prop.Years ago I also went to the PSS dripless stuffing box.Could the PSS be the source of the vibration?

 

[David Foster]

Grounding on the rocks

If there was enough shock to knock loose a connection, it's worth some simple checks:Dive down and have a look at the keel to make sure the damage is limited to a "road ding"Watch for increased water in the bilge. Examine the fiberglass at the back of the keel for small cracks. Since these are most likely to start on the outside of the hull, blow off the paint with a pressure washer, and have a good look when you pull her out in the fall.It's most unlikely that you sustained significant damage, but if you do find small cracks radiating from the back of the keel (as we did on Lady Lillie last summer), then they should be ground away, and the fiberglass properly built up again. If you don't, then the damage is cumulative - the cracks will growth and deepen with each ding until they _are_ a problem.By the way, a haul out, inspection, and the repairs were covered by my insurance. If this is the case, then it's worth doing it now.DavidLady Lillie'77 h27

 

[Bill Murray]

re-check alignment

Many say that if you have your engine/drive shaft aligned while on the hard you should have it rechecked ad=fter the baot ahs been in the water for a little while. IMHO The people who did the alignment should have told you this and maybe offered to re-check it for you.This is because our boats are made of plastic and they can change just enough when floating in water vs hanging in a cradle or jack stands to not get the alignment consistent. There are letters in teh archives on this subject.I would get a set of feeler gauges and re-check their work. your manual should specify what the acceptable tolerance is, or got the archives, or check it out at a good site like the link below....http://www.marinedieseldirect.com/universal/200157/universal-owners-manual-spring-engine-preparation.htmlGood sailingBill MurrayGood FaithH29.5

 

[Will Baker]

Thanks for the reply

They did the alignment after launching, when the boat had been in the water for three days-just like you said, they wanted the hull the "regain its shape."Thank you, this is a great deal of help.

 

[Will Baker]

I appreciate the advice

I am pretty sure that the connection came loose before I ran aground. I had been sailing and then motoring for about twenty miles and ran aground turning into the mouth of Otter Creek-I was bringing her home from Willsboro Bay (on Lake Champlain) to my home "port," a slip that I rented on the Otter Creek five minutes from my house.I ran into a little bit of weather and the waves did give me a rough ride there for a bit, my guess is that's when the connection came loose. It appeared as if whomever had installed that connector cut through most of the wire when they stripped the insulation off the wire.Anyway, (even though it sounds like I am making an excuse I think my depth sounder was giving me erratic readings before I ran aground. I looked at two charts before making the turn into the creek, and since I was suspicious of my depth sounder, when I made the turn I was going very slow.The visibility in the creek and the lake for that matter isn't that great, even though there is ony 12 feet of water at my slip, I don't think that I'd be able to see much. But I have been checking for water in the bilge and there is none, it is bone dry-I was just over to see her this evening as a matter of fact.At haul out, per your advice I will look for cracks at the back of the keel and if they are present have them repaired.I also think that it wouldn't be a bad idea to familiarize myself with my insurance policy.Thanks a bunch for the advice.

 

[Will Baker]

As evidenced by the drips, I am sure I do not

have a "dripless" stuffing box Now could you please tell me what exactly is a "PSS?"