Vibration issue at 3000+ RPM's
 

I had new carb'd 502 long blocks installed this winter. During water test this weekend I noticed a significant vibration 3000 RPM's and above, it phases in and out (it comes and goes), definitely not the norm. I can feel the vibration in the throttles, the steering wheel and through my feet on the floor. The 502's don't sound "synch'd and phased" like the old droning 454's I had either.

This winter I also had HP gimbals installed with new gimbal rings, new engine couplers. The engines are definitely over-carbed, Holley 850's which have to be rejetted or adjusted somehow because they're spitting back up into the flame arrestor if I increase throttle too quickly.

Are these somehow related or separate issues? Where to begin troubleshooting the vibration issue? I don't want to damage anything. The mechanic hasn't had a chance yet to start looking for the problem.

Start by isolating the vibration. Pull the drive off and run the engine. Does it still do it? If so, then you need to start looking closer at the engine. Make sure that the firing order is set correctly. Double check this as it's really easy to make the same mistake twice. I guess the next thing would be to pull the engine and make sure the flywheel in on correctly. Mine was off by 180*. The engine would idle just fine, but when the rpms would come up to around 3k the whole boat would shake. Somebody, for some reason, had cut the dowel pin off the crank. You had to look really close at the crank as it was almost impossible to see where it used to be.

Do you know for a fact that they alligned the drive? Also one more thing that is unlikely but I saw it happen once before is the key in the harmonic ballancer could have broken off and allowed the ballancer to turn a little, or a wrong balancer or something like that. What is the history on these engines? Did you rebuild them or are they take outs from some one else?

Jon

I'm going to the shop today to discuss the plan to troubleshoot this thing, will pass along the thoughts. The only time I can feel the vibration is while water testing, don't recall feeling it when it was on the trailer.

The engines are brand new 502/450HP long blocks from Merc. Took all the bolt-on stuff from my old 454 Magnums, but supposedly they installed a new engine coupler. I'll find out what he thinks later today and let you know. Thanks a million for the quick replies.

One more thing to check is the runout of the coupler. I always make a shaft that barely fits the pilot bore of the coupler splines and then set up a dial indicator to the shaft and turn the motor over by hand. I have seen some out as much as .025. Dont know if that would cause that kind of vibration though but I know it doesnt do the universals any good. When you check the alignment, alway rotate the motor 90 and 180 degrees and re-check it. That vibration you are having sounds more like a motor issue to me though.

Are you absolutely sure the props are OK?

1-Bad prop?

2-When motor back fires when dumping the throttle it is because the air/fuel mixture is 2 lean. Jetting may be too lean or the accelerator pump may be bad or adjusted wrong.

Are the flywheels interchangable between a 454 and a 502 ? If not and they replaced just the long blocks and used your old 454 stuff that could be the problem.

Also Turbojack is right on with the carb thing.
Generally a pop thru the carb is lean and if it stumbles under a load it is rich.

Just got back, they're coming up next week to troubleshoot. The vibration happens with 2 sets of props. My old 3 blades from last season which I know are fine, and a new pair of 4 blades from a buddies boat. They're also going to start with the simple stuff, recheck the alignment, firing order, etc. Along with a new engine coupler, the flywheels were also supposed to be new and included with the long blocks.

The carb problem was confirmed, they told me they plan to rejet them.

I'll follow up when we finally get to the bottom of it and let you know what it was for sure. Thanks again for all the replies to this point.

Make sure the flywheels are correct for the new engines.
The 502 and 454 flywheels are different.
Did they come with the new engines?

I agree it sounds like the flywheels and balancers, but think the vibration would be bad at all rpms and then get worse. I installed a wrong flywheel on an engine once and it nearly shook apart just starting it.

If you have Dennis Moores book it explains the differences between mark IV, gen V and IV balancing, and between cast and forged rotating assemblies. They all take different part numbers. Let me know if you want me to look it up to be sure.

BT :cool:

Mine would idle just perfectly but would shake at 3k.

Haven't solved the vibration issue yet, they're still messing with the carbs. Holley 800's and a dart intake, wouldn't have thought it would be such a temperamental setup, but apparently it is.

Did you get an answer to the flywheel. My friend is going from a 454 to a 502 and said he had to change the flywheel because it is externally balanced (or visa versa).

It shouldn't be tempermental. They should also be dialed in on the water. Can't really dial them in exactly without a load on engine and the boat sitting at the same angle as it does in the water.

Cuda, its a new flywheel installed.

Griff, last night they were running great while sitting on the lift but too dark to put it under a load. This morning it was a different animal, wasn't idling right and had to be feathered to start and warm at 1400-1600 RPM's.. There's no choke on the carbs, he has the choke plate strapped open.

Port motor cut out on me as I was coming up on plane, spitting back like crazy, then I couldn't get it started again. Saturday evening he was adjusting the timing and idle, but didn't rejet yet, says that's next step. I'm assuming all this "dialing in" takes time? I guess this is why factory packages still sell relatively well?

Update:

Took the drives off and reinspected both bearing installations. There was no problem with the alignment, so we're down to the flywheel issue I guess.

Engines were brand new Gen 6 long blocks from Fond du Lac Merc distributor. The flywheels were ordered from another vendor. I'm assuming they shipped and installed the right flywheels, but won't know for another few days, the performance shop is going to double check. In any case, it looks like the engines will have to be pulled. :(

PUT A DIFFERENT SET OF PROPS ON AND TRY THAT FIRST/Darin

Hi Darin, we did that a few weeks ago.

UPDATE: 5/21/03

Engines were lifted and inspected flywheels. Mechanic tells me today he installed new flywheels, made a comment to the effect the ones installed this winter said "Gen 1" on it, and the new ones installed this week said "Gen 2". I'm assuming they installed the wrong flywheels which caused the vibration, and that this will fix the problem. Hope to test next week.

Gee sounds familiar:rolleyes:

Unbelieveable isn't it? :( Should I even mention it's taken 3 weeks to do a 2 day job, and the entire repower project enters month #9 on June 1?

You'll need a 3rd person Ted, I'll can bring my little checklist of things NOT to do. :D I'm only 90% of the way home, but 100% done.

Sounds like progress Kieth. That's a good thing! Not sure in your case, but I think the harmonic balancer and flywheel are a set. Have they looked at the balancers?

If it is any consolation to you, there hasn't been a nice weekend yet, so you haven't missed much. This weekend looks poor as well.

Hope they get it right this time for ya! :eureka:

Dave :cool:

This sounds just like the gimble bearing in the transom. In my old boat, took it to a local shop, they replace my unjoints. still nothing. Took it apart and found that the gimble bearing was shot. easy fix.

bsc

If they went through the trouble of pulling the drive, replaceing the u-joints and NOT checking the gimble when they where in there, I'd find another shop to go to.

My shop replaced the gimbal rings, gimbal bearings, as well as installed the new HP gimbals that do not have the trim senders or trim limits.

I'm curious about the flywheels and balancers piece Blue Thunder. I ordered long blocks from Merc, and was charged for new flywheels, that's all I know.

I'm at the mercy of this shop because I didn't have a place to put the boat in order to do all of this myself. It's painfully obvious they don't know what they're doing. I still owe them money for work completed, but it would cost me more to move the boat over to another shop to re-do some of the work I've already paid for. So while I haven't paid in full, I'm into this for a lot of dollars already.

I'm trying to get to a point where I'm 90% done, and I"ll finish it myself from there. Have no idea about the harmonic balancer, and if that comes with the long block I purchased. If the vibration is still there next week, I'll have no other choice but to take the boat elsewhere and give it to somebody who knows what they're doing.

Are the harmonic balancer and flywheels normally included in a long block purchase? Are they a matched set? These are Gen VI's, my old motors were Gen IV's and it's possible they may have simply swapped stuff over?

Keith, Going from my handy dandy Dennis Moore book (502):

Mark IV - balancer is PN 14097024 and is used with flywheel 3993827, ID # 3973457

Gen VI - balancer 10216339 and is used with flywheel 14096987, ID # 14096805.

The mark IV is set is good for cast or forged assemblies and the gen VI set is only for forged rotating assemblies.

Gen V and VI flywheels/balancers cannot be interchanged with the Mark IV because of the change from 2 pc rear main seals in mark IVs to one piece in Gen V, VIs. The bolt pattern remains the same though so they physically interchange. Bottom line, you cannot put mark IV stuff on a gen V,VI engine. The balancer part numbers are different as well, so I will assume you get an out of balance problem when using the wrong one there as well.

Balancers and flywheels are not a matched set per se, just need to have the correct parts together on the correct engine.

Balancers are easy to change if this turns out to be an issue.

The two long blocks I purchase last year as remanned DID NOT come with flywheels or balancers. I had to reuse my old which was ok in my case. Did you ask if they reused the old flywheel and balancer? If they did, make sure they are changing the balancers now as well. It may be wise to make a call tomorrow to a new merc engine supplier and as the question about if they are included in the purchase when buying new.

Dave :cool:

Dave,

I'm betting the balancers did not come with the long blocks, and I'm betting they used the ones from my old Gen IV 454 Mags. I'll call the shop tomorrow. I'm the patient, teaching the doctor how to diagnose the illness, and treat it, this is incredible.

Thanks a million for the info.

Just following up.

Shop replaced both flywheels with the proper parts, and I tested today. No more vibration at 3000 RPM.

And a final note to everyone who replied, my sincere thanks.

Well that is great news!! Now you can enjoy the summer. You still haven't missed any boating thanks to the mighty poor weather.

Good luck with the rest of the debug. ;) ;)

Dave :cool:

Dave,

Again my thanks to you and the other guys who responded with some great information and detail. I couldn't have done it without you guys.

I still have a major problem with the Holleys running too rich. The guys in my club have provided 3 different names and numbers of holley experts in my area, so hopefully this will be the last piece of my project. At this point, I don't know if it's too much carb, or simply a rejetting issue.

Thanks again.

Kieth... I have two newly rebuilt 1988 quadrajets that I am willing to trade for 800 Holleys, maybe even evenup if the holleys are in good shape. You pay shipping :D :D ;) ;)

Dave :cool:

I bet you would!! :D :D Since I already have the fuel lines and brackets, it would be easier and less costly to stay with the Holleys. Whatever the case, I need to do some research the next few weeks. I loved my quadrajets, only have 1 left unless Woody pulled the other off the engine he bought from me.

By the way, he tore 1 of my 1989 engines down, said it looked like it had 100 hours on it.