View Full Version : Vibration

mc donzi
07-27-2011, 11:22 AM
Morning Guys,

I have a 2000-22C with a 454-385HP Volvo DPX. I have developed a vibration that starts at about 2500 RPM and ends at about 3000 RPM. I think that I have it isolated to the motor because with the drive in neutral(no load on the drive), if you slowly increase the RPM, the vibration comes on at about 2500 and stays until you're above 3000. Running along on plane at between 2500-3000 it seems to be amplified. Below 2500 there does not appear to be a vibration and above 3000(all the way to 5000) it runs great. Also, just to make it more confusing(to me at least), for about the 1st 5 minutes of running time, there is no vibration anywhere through the RPM range. It's after the motor has 'warmed up' it seems. It's frustrating because thats the RPM range where I do most of my running.

When it first started, I found that the power steering pump was loose and tightened it thinking I had solved the problem but after about 5 minutes of running it re-appeared so now I think that the vibration loosened up the P.S.pump.

I wonder if someone else has had this problem or has some ideas.

Chime in guys.



07-27-2011, 12:59 PM
check your harmonic balancer,,put a timing light on the engine and start it,check the timing marks,if its off then your balancer slipped or spun..

also first make sure all the cylinders are firing,that would cause a vibration..

mc donzi
07-30-2011, 06:37 AM
Thanks for the response Fixx. I'm going to have the engine scanned early next week to see if it's a bad plug or bad wire. I live in Ontario and the boat has to be fogged every fall so I'm hoping that it's a plug breaking down in that RPM range.:crossfing:

08-02-2011, 06:05 PM
Does the vibration change if you turn the steering or trim the outdrive? I have seen u-joints with extra play or tight cause this also.......

mc donzi
08-04-2011, 06:59 AM
Does the vibration change if you turn the steering or trim the outdrive? I have seen u-joints with extra play or tight cause this also.......

A 'U'- Joint was my first thought too but it seems to be in the motor because it vibrates with the drive in neutral. I should know better this afternoon after it's scanned. Thanks for your input.


08-04-2011, 07:54 AM
A 'U'- Joint was my first thought too but it seems to be in the motor because it vibrates with the drive in neutral. I should know better this afternoon after it's scanned. Thanks for your input.


Doesn't matter, neutral or not. The drive shaft still spins and the u-joints along with it, all the time the motor is running. The shifting into gear is done in the drive's upper gearing.


Sweet little 16
08-04-2011, 08:58 AM
don't have a any knowledge of the newer volvo drives but with the older drives they could be removed and the motor run . If it can be done with the newer drives that would let you know where the problem lies.

mc donzi
09-15-2011, 09:02 AM
OK guys I've tried all the cheap stuff(plugs, wires, cap and rotor and 94 octane fuel) and the vibration is still there. The local Volvo mechanic(after talking to Volvo tech. support) is suggesting that it is probably the damper/flex plate between the motor and the drive. The motor has to be pulled to check.

The boat has 335 hours on it. The scan revealed the following- 175 hrs-0-1000 RPM, 47 hrs-1000-2000, 67 hrs-2000-3000, 30 hrs-3000-4000 and 14 hrs- 4000-5000.

My question is... should I have the motor rebuilt while it's out????

Thanks in advance,


09-15-2011, 09:21 AM
When the motor is out is a great time to find things to do. The hard part is finding money to do things. If your budget allows it is a great time to check, replace or repair things you can't get to while the motor is in. Bilge pumps, glass work on stringers and transom , if needed paint. As far as the motor is concerned I'll let the motor guys comment.

09-15-2011, 02:22 PM
Your engine does not need to be pulled to check your coupler, just the drive. Could be a dozen things. Balancer, waterpump, plug, valve not closing/opening all the way, u-joints, upper outdrive, etc. When they pull the drive they can look at your u-joints, coupler, bearing and drive and also isolate it from the engine. If it still vibrates it is engine and not drive. Engine can be cheaper to fix than a drive. As far as rebuild goes, if it aint broke, don't fix it. I have always found that new runs better and longer than rebuilt. If not rebuilt engines would cost more than new. Since it only happens after warming up I doubt it would be anything serious. Could be a cracked head taht is injesting a little water once it heats and crack swells. Over 3k there is too much fuel to dilute the explosion...again it could be a dozen or more things. Make sure you have a good and trusted mechanic, not just a dealer or ?

Dr. David Fleming
09-16-2011, 03:16 PM
I would suggest that you re-evaluate your engine on its performance instead of concentrating on the vibration. Some vibrations are serious and forecast an impending mechanical failure. Some vibrations are unique and inherent to motors or are just a common pain that has to be lived with.

Serious vibration the kind that rattles your teeth and starts to crack stuff must be addressed. Engine misfire, crank train out of balance including the drive can be inspected by a good mechanic. Members of this site have been trying to point out a few of these issues. Some uneveness in firing due to fuel distrubution problems or ignition going wayward and valve problems can be some of many sources of vibration.

It is usually not necessary to dissassemble an engine and drivetrain just to diagnose a potential issue. This is very expensive and does not alway reveal anything wrong.

Here are a few rules of thumb. Does the engine perform at speed delivering the performance it always has? Usually any serious engine problems are accompanied by a loss in power and performance.

Second are there any associated noises? Engine and drive noise associated with vibration usually go together.

Technical and physical inspections - You can do a visual examination of the flexplate coupling, and drive joints by pulling the drive. The harmonic balancer is the small flywheel on the front of the crankshaft. It is made of two parts pressed together, have these internally moved out of allignment position with each other? Is everything turning over properly when you do a visual with the engine running. Is the crankshaft moving in and out of the block? Cylinder "leak down" testing will show any compresson leakage and wear on internal components. Is there water in the cylinders? Spark plugs can be read and they tell many things that are happening in the motor. Many engine controllers will diagnose and record engine malfunction - you can get a coded memory readout of these.

A good mechanic should be able to walk you through all this without spending too much. Replacing parts to find a problem is an ignorant way of troubleshooting. You will replace a lot of stuff that is not necessary and help support the mechanic's children through college.

Sometimes you just have to let an issue develop to see more of what it is. Remember the movie 2001 Space Odessy - the HAL 9000 computer diagnosed a flaw in the HR1-9er antenna - when the mechanic went to fix it the HAL computor "knocked him off." Hopefully your Donzi won't do that to you.

Mechanical trouble shooting some engine issues is a real art - you have to use a very high level of intellectual function - to discern issues - ascertain if they are actionable - formulate hypotheses - propose possible solutions - get it repaired at low cost. A good mechanics mental skills are very advanced.

Harley Davidson engines are notorious vibrators - vibration goes up or down depending on the weather and the mood of the motor. Vibration doesn't always mean anything that you can fix.

I remember a mechanic in upstate Michigan who pulled 454 MAG MPI engine because it was misfiring. He did complete engine overhaul and then replaced engine and it still misfired. So he pulled engine a second time and trucked it to Tyler Crocket and had it put on the dyno. The engine misfired because the engine injectors were clogged - Tyler cleaned the injectors engine ran great. All these mechanics did well and the owner paid but never knew.

Good Luck,

09-16-2011, 08:53 PM
Ditto...but you need to isolate the problem by removing the drive, etc.

mc donzi
09-17-2011, 10:57 AM
Thanks for the recent replys.

We're on the same page... I had planned on checking the stringers, transom etc. and have already bought a quart of 'Bilgekote'.

We checked the harmonic balancer.. it's running true(no wobbles) and the water pump was changed in May, 2010.

Dr. David
I also wondered if the vibration was inherent to the engine/drive package so I called Tony Sporer( he has the same setup- 454-385HP Volvo DPX-E4 props) and he has no vibration in any RPM range.
The vibration is not teeth-rattling(it makes the engine hatch cover rattle) but more of an annoyance because it vibrates between 2500-3000 RPM which is the range that I do most of my running in. But I also want to eliminate the vibration before it gets worse.
The boat performs very well(IMO).. jumps onto plane, pulls 5000 RPM that gives me 70.8MPH on GPS. I might even get more now that the air is cool and I`m using 94 octane fuel.
We scanned the engine and no codes were revealed.
I changed the plugs, wires, cap & rotor not because of ignorance but because I`m the 3rd. owner and didn`t know if they had ever been changed. I looked at this as something that would have to be done down the road anyway.
I wasn`t suggesting that I wanted to tear the engine down to find the vibration but was wondering if, at 335 hours, was it time to freshen it up. I was thinking preventive maintenance.

Again, thanks for all your input.


joseph m. hahnl
09-17-2011, 02:15 PM
Seems to me if it where mechanical,such as a flex plate. Vibration would occur through the entire RPM range, getting worse with higher RPM. To me it sounds like fuel air delivery. This being a MPI that would be controlled by an ECM.Not sure what kind of vacuum ports if any are on that engine . My 88 350 mag has none.There are, vacuum ports that have check valves that do open at a certain vacuum pressures.If it does have vacuum ports a vacuum leak could be a source of the problem. Also with it running fine when cold with out vibration,again this does not sound mechanical. Quite possibly it could be a failing sensor that is misinforming the ECM and it is running to rich in that RPM range and is causing vibration.

mc donzi
09-17-2011, 04:03 PM
Thanks Joseph,

If it was a fuel air issue or a faulty ECM.. wouldn't it display a code on the computer scan???


Morgan's Cloud
09-17-2011, 08:17 PM
I've been over this about 5 times now , and not discounting the other suggestions , had you not said that this was a new development and it happens in neutral (as well as running), I would have maybe advised checking the props for absolute trueness.

I'm running the same design propset and I do have a certain throttle setting (when running ) that there seems to be a slight vibration .. then you can drive through it and it goes away .. But so much for that idea.

When engine harmonics come into play odd things can sometimes happen. Even if everything is 'normal' .

Have you checked the engine mounts (all of them) for tightness ? I really hope everyone dosn't think that was a numbskull suggestion .. :kingme:

joseph m. hahnl
09-17-2011, 08:26 PM
A sensor will only show bad in a scan if it has completely failed. I think most code alarms are based on open circuit sensor failure.
If it is the ECM that is creating the problem, I do not believe a code would be generated and a reader would not be able to detect that . The ECM it self may not be the issue only the information that it is receiving for that RPM range.
For instance if the If the Map sensor was working but giving the wrong reading
the ECM would react to it in a negative way.

mc donzi
09-18-2011, 07:45 AM
Morgans Cloud,

In what RPM range does your 'slight vibration' occur?? Mine is between 2500-3000.

Have you ever revved your engine in neutral through the range that yours occurs??

There are NO numbskull suggestions... I appreciate any and all feedback!!

Engine mounts will be checked tomorrow.



Morgan's Cloud
09-18-2011, 11:00 AM
Actually I've never revved my engine in neutral over about 1300rpm ... I sort of baby my stuff you know. I've only noticed it once or twice , but I still have very little seat time on the new package ..Maybe next summer I can get back to testing or having fun again .

Otherwise mine is a 350/5.7 so we're probably not comparing equals here .

A year or two back someone showed me an engine where the lower nuts on the mounts had dropped by quite a few turns , even though the top nuts were 'high and dry' doing nothing , the owner didn't have a clue.
Again , this may not be the problem , but it's an easy one to check. And don't forget the rears too .