Mercruiser 409 engine severe vibration issue

Bondo said:

Ayuh,...... is this an over-bored 400 SBC, or an over-bored 396 BBC,..??

I haven't heard the term 409 since the beachboys did that song, my little 409, back in the '60s,.....

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Quicksilver introduces all-new 409 MPI Bravo engine, a repower option for classic boats

Quicksilver, a brand of Mercury Marine, today introduced its all-new 409 MPI Bravo® FWC engine at the Land 'N' Sea Marine & RV Show in Las Vegas.

powerboat.world

Voyager NY said:

I recently purchased a Certified Pre Owned (CPO)engine from Doug Russel Marine. The engine was installed and at first start up i noticed a high vibration from the engine , this is before the drive was installed. The engine was aligned with the coupler ,drive installed and boat launched. The vibration was immediately apparent while under way. After reporting the issue to the marina mechanic it was thought to be a misfire. Now after extensive evaluation by another certified merc mechanc and mercruiser tech support the vibration at all speeds is still there.This is what has been done new plugs cap and rotor change engine coupler, remount sea water pump(it fell off) change motor mounts, replace oil pressure sender(it fell apart) oil changed from 25-40 to 25-50 My question is does anyone out there have a 409 and have you experienced excessive vibration (the whole boat is vibrating to the point everything is shaking, coffe cups jumping out of the holder.
Please help

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Voyager NY said:

There was a 383 mpi in there previously and the engine is a new CPO motor from quicksilver designed 409 for a direct replacement for older 350/383 engines,this motor is from merc.

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Voyager NY said:

I recently purchased a Certified Pre Owned (CPO)engine from Doug Russel Marine. The engine was installed and at first start up i noticed a high vibration from the engine , this is before the drive was installed. The engine was aligned with the coupler ,drive installed and boat launched. The vibration was immediately apparent while under way. After reporting the issue to the marina mechanic it was thought to be a misfire. Now after extensive evaluation by another certified merc mechanc and mercruiser tech support the vibration at all speeds is still there.This is what has been done new plugs cap and rotor change engine coupler, remount sea water pump(it fell off) change motor mounts, replace oil pressure sender(it fell apart) oil changed from 25-40 to 25-50 My question is does anyone out there have a 409 and have you experienced excessive vibration (the whole boat is vibrating to the point everything is shaking, coffe cups jumping out of the holder.
Please help

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Voyager NY said:

I recently purchased a Certified Pre Owned (CPO)engine from Doug Russel Marine. The engine was installed and at first start up i noticed a high vibration from the engine , this is before the drive was installed. The engine was aligned with the coupler ,drive installed and boat launched. The vibration was immediately apparent while under way. After reporting the issue to the marina mechanic it was thought to be a misfire. Now after extensive evaluation by another certified merc mechanc and mercruiser tech support the vibration at all speeds is still there.This is what has been done new plugs cap and rotor change engine coupler, remount sea water pump(it fell off) change motor mounts, replace oil pressure sender(it fell apart) oil changed from 25-40 to 25-50 My question is does anyone out there have a 409 and have you experienced excessive vibration (the whole boat is vibrating to the point everything is shaking, coffe cups jumping out of the holder.
Please help

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Scott Danforth said:

something is most likely wrong with the base engine level. did they use the old flywheel vs the flywheel on the 409?

as AD asked, what was there prior to the 409?

there should be no vibration strong enough to shake a coffee cup or brake sea water pump fasteners.

did you mechanics do a power balance test? that would tell you if you have a dead cylinder.

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Voyager NY said:

I recently purchased a Certified Pre Owned (CPO)engine from Doug Russel Marine. The engine was installed and at first start up i noticed a high vibration from the engine , this is before the drive was installed. The engine was aligned with the coupler ,drive installed and boat launched. The vibration was immediately apparent while under way. After reporting the issue to the marina mechanic it was thought to be a misfire. Now after extensive evaluation by another certified merc mechanc and mercruiser tech support the vibration at all speeds is still there.This is what has been done new plugs cap and rotor change engine coupler, remount sea water pump(it fell off) change motor mounts, replace oil pressure sender(it fell apart) oil changed from 25-40 to 25-50 My question is does anyone out there have a 409 and have you experienced excessive vibration (the whole boat is vibrating to the point everything is shaking, coffe cups jumping out of the holder.
Please help

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Voyager NY said:

My thought is at this point is that the motor has a internal balance issue but merc is fixing all the things that are breaking due to the vibration but are saying that the vibration is normal. I could see at idle due to the flat crank but this vibration is at all rpm's The LP fuel pump and the oil filter are shaking wildly

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