A shudder in neutral/idle

[bravenewworld]

During a recent sail delivery of a 2003 Jeanneau 39 Odyssey I experienced a continuous shudder in neutral at idle that did not seem to come from the engine itself but rather the transmission. The owner, upon my delivery of the boat, mentioned a similar experience. The engine mounts were fine as were the shaft alignment, cutless bearing, shifting electronics and related mechanicals, seals and linkages. The tranny seals were tight and there was only minimal lubricant leakage from either the engine or tranny. A first rate marine engine maintenance mechanic was unable to find the cause of the shudder. In forward or reverse gear the shudder disappears completely and the 28hp Yanmar engine runs like a top all the way through the range including at near idle in forward or reverse. Does anyone have a similar experience and some idea of what the cause might be?

[four winds]

Are you sure the idle RPM is correct? Too low?

[tkeithlu]

Ditto to fourwinds, but also is the "shudder" transmitted to the drive shaft? Could it possibly be not quite in neutral?

[a64pilot]

In neutral the transmission isn't "doing" anything, how could it shake?

[donradcliffe]

Were you sailing at the time?? How fast? Fixed/folding/feathering prop?

[shakey doug]

Drive Plate ? Loose Flywheel ? Freezer/ Aux PTO.

[Sailmonkey]

idle too low......my best guess. use a photo tach to confirm the idle speed

[sck5]

I had exactly that problem on my old boat which had a Yanmar 3gm30. Turned up the idle a little and it went away.

[bsurvey]

it may be the springs rattling on the damper plate

[sheldon957]

Originally Posted by sck5

I had exactly that problem on my old boat which had a Yanmar 3gm30. Turned up the idle a little and it went away.

Agreed!

[Mendana]

Hi There bravenewworld.

If your engine is above the exhaust water trap (or muffler) then it could be tapping it when in idle....or possibly tapping against the hull. If it makes an unusual sound it is likely that it is something like this. It can be a a problem if left unchecked.

Get a torch and your head under the engine and have someone move the revs up and down out of idle.

[sailersteve]

I wood like to tell a story about a transmission problem .And this is for any boater ! IN the early 90's i started working in a shop and started finding 454 Chevy motor parts all over this shop , parts i had no idea what they were ,the place was a wreak everything everywhere. A short 454 big block in a plastic bag , four big block heads in plastic bags etc. One day i asked about the motor parts and find out they are to a 30ft searay 12ft beam , twin 454's , twin turbo charger on each motor. This guy was away's good to me so i thought put them together putem in the boat ( I'd never worked on a boat before ) Lots to learn and a hole lotta parts i'd never seen before . Right now you'r thinking what does this have to do with a transmission problem ? Well you can either keep reading and find out ,or stop reading and never know something about velvet drive transmission's . Anyway here i go again . SOMEONE had stolen one of the newly rebuilt 454 short blocks in it's plastic bag. It's a pretty big plastic bag to put a 454 short block in, but the price of a new or rebuilt short block to marine specks to match the reverse gear 454 big block twin turbo was like 4 grand at the time . Keep reading it gets better what else you got to do you already ate you should be kicking back in joying your boat . At least you're on your boat this guy's not even on his boat yet ! I'd been having Shoreline engines Laskey rd Toledo (out of business as far as i know ) rebuild motors for me for awhile like maybe 5 in that same year. One great guy built all the best drag car motors fr

[sailersteve]

From Detroit to Norwalk speedway Ohio.For the life of me can't remember his name. . Great guy when i tood him what happen to my buddy's motor he checked his shelf's , he had an empty big block 11:1's pistins , correct cam and crank he build my buddy a matching marine motor for $1100.00 bucks brass soft plugs and all . Ok here's where it get good i hope ! I adjusted the rockers with the feelers for a start and did it after worm up buy feel and sound as i was taught on my big block corvette and both motors seemed to run fine . But the port side transmission made a small rink,rink,rink nose at idle . I'd pulled that tranny out 4 times ,it was pulled apart each time and each time everything was perfect all bearings all shifter parts each and every time after i'd put it back in i'd do the same thing . After the fifth time of pulling it out and having it completely rebuilt . I'm sure you all can guess rint rint rint at idle . Remember i'm doing all this as a favor being nice . Building twin 454's with twin terbo's each putting them in the boat alineing the shafts all the hose's, wiring everything everything i'm going out of my mind over a transmission ! Here it is the big finish . When we took the new rebuilt trans back to the guy he asked DOES THE PORT SIDE MOTOR RUN PERFECT NOT A MISS AT ALL ? We went back and listened and guess what it had a slight miss . The number 5 cylinder a slight miss showed up from a compression check , the intake valve was 1/8 of a turn to tight after taking off an 1/8 of a turn the motor ran perfect and the transmission never made the rint, rint ,rint ever again . And the moral of this story never ever forget this story and never ever offer to put in twin 454 's w/twim trbo's in anyone's boat ever ! Thanks for reading !