Engine Vibration

A

AllTideUp

Member
May 6, 2013
200
Northern Virginia
Boat Info
2003 SeaRay 380 Sundancer
Engines
8.1s - 370HP
Hello all!

I'm the owner of a "new" to me 2001 340DA with Horizon 7.4 MPI engines and V-Drives. I'm loving the V-Drives right now but I am trying to track down the cause of a vibration in one motor. I've tried a couple things to find it but figured I'd see if anyone else has some insight.

I just purchased the boat 2 weeks ago from a dealer. When we were going thru the boat it was found that the props were damaged so they took those off and put a different set on. They also had to align the engine/trans as they were a little off with the shaft. When we did the first test of the boat before changing the props (or any other work) I did not notice any vibration. When we picked the boat up I noticed it and thought it could be due to the change in props.

I have already spoke to the dealer and they sent the original props out to recondition them and I should be getting them back today. Hopefully this fixes the issue.

The vibration happens when the engine is in gear and the rpms are ~900-1000 and higher, but only on the starboard engine. The port engine doesn't cause it. The vibration is enough to feel through the boat and I opened the engine bay to look once and you can see the motor shake a little when powering up, while the port motor doesn't do the same. If the motors are not in gear and you power up the motor doesn't shake.


I also went and checked the cap n rotor to see if it needed replacing, it is worn and has a little build up but nothing that I think would cause this, I was also going to check plugs today before taking it back to the dealer to swap out my props.

Any other ideas? :huh:

Thanks
 
I would change the cap and rotor first thing. Then check spark plug wires on both ends. I had the same vibration and same symptoms as you. I also had a cap that had very little corrosion on the contacts. New cap n rotor fixed the problem for me.
 
scoflaw said:
When the plugs are out would be the time to check for a weak cylinder or 2
Click to expand...

I had the dealership do a compression test before purchasing and all cylinders on both motors were 135-155.

Saverio said:
is it the same motor they had to align the shaft with. mabe they left something lose
Click to expand...

I'm not sure if it was the same motor they had to align. They discovered the alignment issue without me there and just fixed it for me.

jason78 said:
Different engine, different 340 hull, same problem. Root cause was a bad and/or loose spark plug.

http://clubsearay.com/showthread.php/64456-Vibration-in-Starboard-V-Drive-Shaft-or-Transmission
Click to expand...

Thanks for that link! I would have tried to check the plugs but when I was checking the cap n rotor I found a plug wire loose and thought that would be it. So I went and tested it out, wasn't the cause but by then the manifolds were too hot to work around so I'll be looking at that today.

Knot It said:
I would change the cap and rotor first thing. Then check spark plug wires on both ends. I had the same vibration and same symptoms as you. I also had a cap that had very little corrosion on the contacts. New cap n rotor fixed the problem for me.
Click to expand...

I may just do that. I'm thinking of just changing the cap n rotor and plugs all at the same time and get it over with.


Another thing is that the marina said they put replacement props of the same size on and now one motor (port) revs to ~4900 WOT while the other (starboard) only gets to ~4300-4400. I was thinking they either put a wrong prop size on or that this could be a non-firing cylinder problem too. But, I thought that 4900 rpm for the 7.4 310hp engine was a bit high. Isn't it supposed to be more like 4400-4600 or so?
 
4900 is high. You should have a plate on your motors that state the recommended WOT RPM range. I have same motors and mine are 4000-4600



Sent from my iPhone using Tapatalk
 
mquiet said:
4900 is high. You should have a plate on your motors that state the recommended WOT RPM range. I have same motors and mine are 4000-4600
Click to expand...

Thats what I thought. I think the Horizon 7.4 MAG is supposed to be rated to 4900 but the regular 7.4 was lower. I should be getting my original (reconditioned) wheels back today so hopefully that fixes that problem.
 
id be willing to bet the replacement prop has a tweak in it. I just went thru this last week, somehow one of the prop blades got pulled back slightly about a quarter inch, unrecognizable by eye, and that's all it took. port motor was fine, starboard motor as soon as I got to about 1000rpm, the windshield would start rattling. put on my spare props and cleared it right up
 
Disposable Income said:
id be willing to bet the replacement prop has a tweak in it. I just went thru this last week, somehow one of the prop blades got pulled back slightly about a quarter inch, unrecognizable by eye, and that's all it took. port motor was fine, starboard motor as soon as I got to about 1000rpm, the windshield would start rattling. put on my spare props and cleared it right up
Click to expand...

Hmm.. Just takes time to track it down I guess.. Hoping to get this thing ironed out today. I have a ~150 mile trip coming up and would prefer not to have it just fixed right before we leave.
 
AllTideUp said:
Hello all!

When we were going thru the boat it was found that the props were damaged so they took those off and put a different set on. They also had to align the engine/trans as they were a little off with the shaft. When we did the first test of the boat before changing the props (or any other work) I did not notice any vibration. When we picked the boat up I noticed it and thought it could be due to the change in props.

I have already spoke to the dealer and they sent the original props out to recondition them and I should be getting them back today. Hopefully this fixes the issue.

The vibration happens when the engine is in gear and the rpms are ~900-1000 and higher, but only on the starboard engine. The port engine doesn't cause it. The vibration is enough to feel through the boat and I opened the engine bay to look once and you can see the motor shake a little when powering up, while the port motor doesn't do the same. If the motors are not in gear and you power up the motor doesn't shake.

Thanks
Click to expand...
How do you suspect the props were "damaged". When we wrapped our own stupid bow-line in the port shaft NYE, we had to have the prop and shaft re-tuned at the prop shop. The rope had wrapped up the shaft and pushed it don into the hull chunking out some fiberglass. The prop shop was able to straighten the shaft, and repair the port prop. On the Starboard side we had them install new shaft seals, and a new strut bearing. This introduced me to the alignment issue. The new strut bearing created a situation where they had to re-align the starboard engine and transmission. So, in the drive train, Propellers, shafts, and alignment, can all cause vibration. If the vibration is in the secondary electrical system, and only manifesting when the engine is loaded, a scanner like the Rinda scanner can usually tell you which cylinder is misfiring. Even if it is not enough to set a code, the data stream will point out the faulty cylinder. As has been suggested, just checking the plugs and wires is a good place to start. especially if you are adept at boat yard yoga, and do not have access to a Scanner.
 
My money is on mis-matched props. You should be spinning 44-4600 RPM at WOT. I've seen dealers put not only different pitch but different diameters on the same boat. Both props came fresh out of the box. Rotten QA across the board.

As far as the vibration, what tolerances are they giving you. An engine out of alignment will cause MAJOR drivetrain problems down the road.
 
Ok, so swapped my props to the reconditioned originals, before with the originals could only get about 4200-4300 rpm, they changed the pitch a little and now my engines over rev back to 4900 again. I doubt they will pay to have them re-pitched again though. On then plus side both engines now seem to put out the same power and when accelerating increase at the same rate.

On the down side, the vibration is still there. Tech tested and made sure all cylinders were firing but when he was pulling the wires from the distributer one of the contacts on the distributer pulled right out.

Think my next step will be new cap n rotor and plugs since I'm down there anyway.

With the new props I'm turning ~3300 rpm with a GPS ground speed of about 25-26 mph.
 
Your speed if right for 3300... That is what my boat does which is exacatly the same as yours. I would check the bolts where the shaft is attached to the transmission and to make sure the bolts are all tight... It is hard to get in that location but a it would not hurt to put a wrend on the bolts make sure they are tight...
 
rcknecht said:
Your speed if right for 3300... That is what my boat does which is exacatly the same as yours. I would check the bolts where the shaft is attached to the transmission and to make sure the bolts are all tight... It is hard to get in that location but a it would not hurt to put a wrend on the bolts make sure they are tight...
Click to expand...

Glad the speed is right, just weird how I can still over rev. I'll just have to make sure I dont go WOT, but not like I ever do that anyway. I like whats left of the money I have in my wallet! LOL

Thanks for the tip on the bolts, I'll look at those next time I'm out there as well.
 
AllTideUp said:
Glad the speed is right, just weird how I can still over rev. I'll just have to make sure I dont go WOT, but not like I ever do that anyway. I like whats left of the money I have in my wallet! LOL

Thanks for the tip on the bolts, I'll look at those next time I'm out there as well.
Click to expand...

I am always suprised the the mistakes mechanics make, like forgetting there tools, and not tightening all the bolts...
 
Ok... So far we now have reconditioned props that fixed the rev issue and I have now replaced both cap m rotor and new spark plugs. Engine still runs fine but the vibration on the motor is still there. All cylinders are also firing.

looking for ideas.. Bad motor mount??
 
anybody inspect or indicate the shafts during any of this? might have a bent one. your running out of rotating things that could possibly be unbalanced
 
Disposable Income said:
anybody inspect or indicate the shafts during any of this? might have a bent one. your running out of rotating things that could possibly be unbalanced
Click to expand...

I spoke to the dealer yesterday and he said that the owner and the tech are gonna sit down and figure out what the next step is and what it could be. Hopefully I'll give it back on Tuesday and they can solve it, but no not sure if I could do anything with the shafts. They have to pull the boat again to check that right?

I thought about trying plug wires as well... They look like they might be original with the boat and have a date of 1Q00 (guessing that means 1st quarter of 2000).
 
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