Bad vibration at low rpm

nextboat1

Petty Officer 3rd Class
Joined
Mar 17, 2013
Messages
82
Hello all,
Ill start with a little history on the boat. Its a 1998 Rinker Captiva 232 with a Mercruiser 5.7 mated to an Alpha Gen II drive. I purchased a new engine for the boat this winter and had it installed by a local marina about a month ago. They were hired to drop engine in, replace the coupler, gimbal bearing, and align the engine. I then took the boat home and finshed the restof the install. When it came time for me to install the outdrive I could not get it to slide on. I got it almost to the mounting studs where I could just barely get a nut started. I checked the alignment with my tool and sure enough it was off. I could only get it to slide in about half way, and the marks were heavy on the top. I then took it back to the marina. They said that they double checked the alignment and all was fine. They said that I need to have the alignment tool that was made to slide into the newer style couplers that have the "snout" and that I must have the other style tool. So, I took the boat home and finshed up the rest of the install. Upon first start up I noticed a very bad vibration at idle. It seems to go away as the rpms increase, but shakes the entire boat at low rpm. I called the marina again suspecting alignment/coupler and they told me to pull plug wires to be sure that is not a dead cylinder. The engine starts easily and seems to run and sound great minus the vibration. Am. I wrong to suspect the coupler or alignment? The engine, coupler, flywheel, fuel pump, spark plugs, cap, roter, ing. sensor, coil, gimbal bearing, exhaust mani's/risers and rear motor mounts are all brand new. The carb was also rebuilt. Any help will be greatly appreciated.
 

NHGuy

Captain
Joined
May 21, 2009
Messages
3,631
Pull the drive back off, and start the engine for 10 or 20 seconds dry. If it does not shake good. Then run back and look inside the transom entry to see if the coupler has any visible runout. Don't run it much over 45 or max 60 seconds.
It sure sounds like baloney about the tool. I would suspect misalignment too. If they are truly in the wrong maybe you need to "yelp" or "angies list" about that shop.
I have a gen 2 coupler on the floor in my garage. I just stuck my align bar in there, it fits fine.
 
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nextboat1

Petty Officer 3rd Class
Joined
Mar 17, 2013
Messages
82
Thanks NHGuy. I have had some other work done by this shop with great results in the past. I actually dock my boat there in the summer. I just want to be sure that I am on the right track. I spoke with the owner and he said that if it is in fact the coupler that they would replace it under warranty. Is there anything else worth checking before hand or should I just send it back to the shop?
 

NHGuy

Captain
Joined
May 21, 2009
Messages
3,631
Keep an eye on your thread, folks with more knowledge than me will be along. Some of them do this for a living.
Perhaps it's your gimbal bearing, universal joint, alignment, or drive.
 
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Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,363
I tend to believe the alignment too vs their word.The good part is they said they would replace it when the new one fails in under 20 hours.
 

Bondo

Moderator
Staff member
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Apr 17, 2002
Messages
71,139
I called the marina again suspecting alignment/coupler and they told me to pull plug wires to be sure that is not a dead cylinder.

Ayuh,..... So did ya try pullin' spark plug wires,..??

Did ya go over the plug wires, to be Sure they go to the right cylinders,..??
 

nextboat1

Petty Officer 3rd Class
Joined
Mar 17, 2013
Messages
82
I'm gonna head down to the boat today after work and try pulling the wires off one at a time. It seems to run nice and smooth with the rpm rasied a bit over idle, so Ill be suprised if it shows anything. After that, its out of the water and back to the shop I suppose. When I had it on the trailer I didn't notice any engine miss by listenting to the exhaust either. Being that the drive is hard to remove/install im really starting to believe that its the coupler or alignment. I also tried my alignment tool in the old coupler last night and it slid right past the "snout" and into the splines. I have also double checked my firing order.
 

nextboat1

Petty Officer 3rd Class
Joined
Mar 17, 2013
Messages
82
Just got done running the boat. I pulled the plug wires one by one and noticed an apparent difference pulling each wire. I then looked back behind the engine and noticed that the snout of the coupler (part with the grease fitting) seemed to have a fair amount of runout at idle. Should that have any runout at all or should it be running completely true?
 

NHGuy

Captain
Joined
May 21, 2009
Messages
3,631
The driveshaft should appear just about stationary. The coupler could have a grease fitting on it that looks like runout.
 
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