alpha one gen 2 vibration clunking

[heath454]

ok guys...this is the deal.. first let me say i am a mechanic. just not a boat mechanic. although i have worked on several.. so im not totally ignorant. my boat is a 1995 18ft starcraft. 4.3 4 barrel carb.....alpha one gen two.. i bought it last year towards the end of the season.. I test drove the boat ran good worked good other than a slight vibration . i was sure it was just a gimbal bearing so i was ok with that.. we ran it the rest of the season and all was good except the slight vibration that never got worse. winterized the boat and that was that. a month ago i pulled lower unit and put in new gimbal bearing with the alignment tool. let me say that the old bearing did not seem bad to me at all..Put it together hooked it to the hose and started it up.vibration seemed the same but when you would drop it into gear and let it idle , it has a random clunk sound in the back of the motor upper gear case . sound like its the u joints or gimbal or something in that area.so i pull it back apart. i then realize that i screwed up and didn't get the gimbal bearing seated all the way in the housing. so i got another new gimbal and reinstalled. made sure it was all the in and took grease. all good.. reinstalled and same issue.clunk clunk ... so took it back out gimbal is full of grease ..alignment looks good. so i took the spanner nut out removed the upper shaft and installed new u joints went ahead and put new bearing and race in reset bearing preload reinstalled. same issue clunk clunk. so i decided to take it to the lake and just se... maybe it was just some backlash or something due to no force on the prop... so i took to the water.. once in the water didnt notice the clunk. maybe because of the water exhaust engine noise ETC.. BUT the vibration is still here and with the out drive trimmed all the way down turned to the left it gets a little worse chatter and vibration and when you turn to the right it chatters and vibrates so bad it almost causes the water to ripple. boat runs fine turns 4800rpm planes out fine but has alot of vibration., so me being who i am i start looking into other things and tearing things apart looking for this issue. i start to assume maybe the engine coupler is going bad. maybe the center of the coupler has tried to slip and is slightly cocked causing the shaft to put some side load on the gimbal. so i convience myself to pull the engine. everything looks fine. i have even started the engine in the shop floor so i can watch the coupler and the flywheel. all looks true and strait as can be.. harmonic balancer hasn't slipped nor is the rubber coming out of it. i have ran compression and all the cyl. 145lb every cyl. ignition is good. runs great. just vibrates and the u joints are binding.. and clunk.. you can even see on the double u joint coupler were there are some markings that is evidence of them making contact. there are no loose bearings or missing teeth in the drive unit. no metal shaving in the oil. no excessive play in the prop, nothing i cant find a thing . what could make the joints bind up.. what could be clunking.. why the vibration... did something get damaged when i put it together with gimball not all the way in. or could it be the bushings in the gimball housing . there is some play in them but idk how much would be to much. i am stumped just afraid there is something that is going to fly apart..

 

[Scott Danforth]

are you shifting the boat on land, or are you shifting it in the water.

on land, the clunk is the dog clutch slamming.

did you align the motor?

 

[achris]

The clunking on land is quite normal, hear it all the time, I ignore it. It's the natural variation of the engine idle speed causing the clutch dogs to chatter.

Your vibratioin. Did you notice if it was there when you ran the engine out of the boat?
Uni joints binding/making contact. Need some pictures of that...

Chris......

 

[heath454]

when i say clunking noise i mean it clunks randomly while the boat sets and runs at about 8or900 rpm in gear. its not the clunk when you drop it in gear.i could see it being a normal thing when on the hose. i just have never herd any other boat do this.. the vibration idk.... i started the motor in the boat with the out drive out .. still seemed to vibrate the back of the boat really bad. tools were falling of the back..i took the motor out to investigate the coupler. flywheel harmonic ballancer etc. i started it on the shop floor and its as smooth as can be..do these motors have a rufness to them in a boat by nature.. are there any kind of ruber mounting on the back mounts mine look to be just a solid mount nothing to absorbe any natural engine vibration., i know when in a pickup or blazer they are kind of ruff or somewhat unballaned. i am going to reinstall all the parts with a different spline yoke long shaft . maybe its slightly bent. putting gimbal bearing in a bind. im lost. it looks plain as day that there are places on the ujoint yokes that have touched. made slight contact.

 

[achris]

I know the random clunking/chattering you're referring to. It's normal and we hear it every day...

Vibration. With the drive off you still have it. Then it's NOT the gimbal bearing. Are you sure you have a balance shaft engine with the standard mounts? Could the engine have been changed at some stage and a non balance shaft engine put in its place?

Chris.

 

[heath454]

engine looks to be all original. no signs of being changed. has original mercruiser tag on it . thick black paint on every bolt head and gasket seam. has the timing cover with the funny looking top on it for the balance shaft.motor is smooth as silk on the shop floor. i am lost. i was going to change my long yoke shaft with spline. so i took it off the u-joint.then decided to to make a little jig using my old gimbal bearing then use a dial indicator on the end of the shaft and turned it slowly. almost no run out in the shaft.so i am fully convienced there is no issue there.like i say vibration was there with lower unit out. maybe that is somewhat normal. it is a long stroke v6 mounted in a fiberglass shell. the bad ujoint chatter when turning hard right and somewhat bad to left worries me. but there is nothing wrong that i can se. maybe i am not getting alignment done correct. maybe it is cocked on way thus being the reason it chatters worse to the right than it does to the left.maybe the engine was installed slightly crooked from the factory. seems to me that if engine was off a little the movement in the gimbal bearing could just **** off center a sligtht bit making it align strait with the coupler and splines but still off center of the gimbal housing.. i hope that makes sense..

 

[heath454]

an updated and another question.. i put boat back together and we have run it all weekend. i have ran it hard. we have pulled tube and ran it wide open off and on all weekend. i even put it in some hard turns while still in the throttle pretty good. it vibrates like crazy when you turn it. but has not flew apart.. is it possible that there is to much play in the bushing in my gimbal housing ring. the pins were it all piviots. is it possible they have to much play in it and has the ujoints out of alignment... i know they are loose they have some play in them forsure. but how much would be to much.. it will move up and down and side to side.. like i said how much is to much???

 

[heath454]

when i have m out drive off you can move the gimbal ring up about a 1/4-1/2 inch could this be causing the ujoints to be out of align???

 

[Rick Stephens]

Sounds like crappy u-joints to me. I'd be replacing them. You can use automotive ones, lots cheaper and exactly the same thing.
Alternate U-joint part numbers....

Any time you hear noise and vibration when you turn you should suspect u-joints. Even new ones can have needles missing or a problem. All it takes is a teensy flaw.

The gimbal ring shold have a little vertical movement, like 10 thou. It is adjusted by moving the entire ring down.

 

[heath454]

i suspected u=joints to. that is why i changed them. and it didnt help at all.

 

[Rick Stephens]

i suspected u=joints to. that is why i changed them. and it didnt help at all.

Still sounds ilke uJoints. Not much else will vibrate and rumble when you turn.

 

[heath454]

I put moog ujoints in it..315g

 

[heath454]

the question to me is .. what is going on that is making the ujoints be miss aligned or out of balance. causing them to chatter .i do have about .040 thou of up movement in the pins and alot of side movement but is it enough to be putting the ujoints in a bind..???? idk

 

[achris]

40 thou! .... There should be NO movement...In any direction....

 

[heath454]

I put a jack and a block under it jacked up on it real slow..lots of slop.. way over 10thou

 

[heath454]

I used feeler gauge up at the top..havnt actually measured it down at the bottom yet..it was over 40. Up above the outdrive werw the pin is

 

[Rick Stephens]

40 thou! .... There should be NO movement...In any direction....

Spec is .001 to .010. Not no movement. You can feel .010 shaking a bell housing up and down. Still, it ain't much.

I would say first priority when setting up this transom is get everything in spec. There is no place I know of to measure play at the top of the gimbal ring. Needs to be measured at the bottom. If the pin is worn, replace it. If the fiber washers are worn, replace them.

 

[heath454]

Is there a kit to buy with washers sins etc,?

 

[Rick Stephens]

Is there a kit to buy with washers sins etc,?

Not that I know of, think you have to order up individual parts and pieces. With your description you probably ought to partially disassemble the transom, remove the bell housing and start from there. The lower pin is nylon, I think. It can get worn. The washers on the two tilt pins are fiber. I don't remember what the lower washers are made of. You can get them out by removing the lower pin, don't have to disassemble the upper pivot to R&R the lower pin.

 

[heath454]

Im going to jave to figure out how to get this all apart