2001 7.4 MPI Vibration

Every Day

Recruit
Joined
Aug 22, 2003
Messages
2
I am asking for any thoughts or suggestions on this vibration.<br /><br />First of all the engine is a 2001 Merc. 7.4 MPI BIII eng. sn OL644969. in a 2001 Bayliner 2655.<br /><br />This vibration started approximatly at 40 hr's. I first noticed it while cruising at about 3200 rpm's, this is a rhythmic/cycling type of vibration that is only noticed between 3100 to 3600 rpm's, engine idles smooth.<br />The shop has determend that it is an engine vibration by running it with the out drive off the boat.<br /><br />First thing done was a cylinder drop test which showed that when #5 cylinder was cut out (dropped)rpm's incresed 5 to 10 rpm's and not decrease as normal. All electrical connections to the injector and spark plug where checked, all of that checked out good. All spark plugs where pulled and they all look normal and all the same condition. Compression has been checked and it was normal.<br />Conclusion was that # 5 injector was bad so they replaced it but the vibration still remains.<br /><br />On Monday they plan to do a leak down test to check further for compression problems.<br /><br />This vibration has been going on for about 80 hr's and I have noticed oil starting to leak from the rear main oil seal.<br /><br />Shop has been very good to work with. They have been in contact with Merc trying to figure this out. They and I are running out of idea's on what could be causing this.<br /><br />I have babied this boat from day one, never have I hit anything with the prop or miss treated it in anyway.<br /><br />Your thoughts would be greatly appreciated.<br /><br />Thanks
 

boat doc

Petty Officer 3rd Class
Joined
Aug 20, 2003
Messages
83
Re: 2001 7.4 MPI Vibration

As a marine service advisor, no trying to be short, but if you have it in a shop, I would let them jack with it, and not let any of us scare you with what it could be's. I get guys all the time that say, "well I heard it could be". It gets hard trying to take the stuff out of peoples head, that someone else put there. If they are certified (and they are if they are talking to merc), they will figure it out. If they can not figure it out, merc will send out someone that can. That does sound kind of curiouse though, I will have to see if there are any service bullitens that describe such a problem.<br /><br />your borderline on that warranty arent you?, unless you purchased as a closeout<br /><br />going against what I was preeching, I started thinking about it, and had to add this..... <br /><br />I wonder if the harmonic balancer slipped
 

Every Day

Recruit
Joined
Aug 22, 2003
Messages
2
Re: 2001 7.4 MPI Vibration

Thanks boat doc for the advice on letting them handle this, the last thing I want to do is cause problems with the repair shop. <br /><br />Interesting that you are not the first to suggest a possible harmonic balancer slip.<br /><br />I feel that they are doing everything that they can. I feel that I have a pretty good relationship with them. The sevice manager even asked me to let them know if I hear of any possible causes.<br /><br />My fingers and toe's are crossed....<br /><br />Thanks
 

boat doc

Petty Officer 3rd Class
Joined
Aug 20, 2003
Messages
83
Re: 2001 7.4 MPI Vibration

well good luck to you, I hope you are still under warranty, as these problems can get expensive. Just keep in mind that any advise that is given is done so without anyone seeing the boat. I would love to know what you find out when they fix it..... I may see the same thing one day. I have 2 guys that run 454's, and they always have minor problems, but they also only run there boat 1 or 2 times a year.
 
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