Stuck rear engine mount bolt
 

Just in the process of removing my 454s from my 272, i'm having a real problem with one of the rear engine mount bolts that locate through the bell housing and into the transom plate. It's absolutely jammed solid. Tried an impact wrench and huge extension bar but it just wont budge. All the others came out no problem. contemplating grinding the head off but there isn't much room down the back of the motor!

Any ideas on how i can undo it would be appreciated??

Cheers
Steve

I had the same problem with a 502 years ago, I threaded a rope through the mount, and lifted the mount off the bolt with the aid of Poole Boat Parks fork lift truck.

try some wd-40 on the under side of the mount and bolt threads if you can get to them, be careful cutting the head off the bolt it may be hung up inside the mount itself. also you may want to try a long extension and a breaker bar before you put an impact wrench on it.

Good advice from Past Due. I would have thought that would be step one before even asking on here.

If you cut the head off the bolt, and it is stuck that bad, you will for sure be into a new inner transom plate. Might try heat just in case someone did the red lock-tite deal. Have you checked the other mount bolts for evidence of lock-tite? Normal cautions as to the use of open flames in an engine compartment would apply here!

You can cut the heads off and put heat to it and the rubber motor mount will melt then you can press in a new motor mount in. Be careful boats & gas dont react to well to heat .

Soak it at the threaded area with WD-40 or PB Blaster. Let it sit for a day to get in there. Before you try to remove it, use a bar or similar item and pound the top of the bolt to send vibrations thru it to loosen it up. Those bolts are made of aluminum so it is probably just stuck. Also the longer the extension you use, the greater you reduce the actual torque at the socket due to the bar twisting. Try to use as short an extension as possible.

Good luck to you, I've been there! I had this same problem on a Scarab a while back. I wound up borrowing my friends 3/4 drive impact that he uses to service his dumptrucks. It got loose thank god, but did wreck the mount.

Thanks for the comments guys. have tried a mix of extensions and bars but it wont budge. The others came out no problem at all and no evidence of loc-tite. have soaked it in WD40 and given it some good knocks with impact wrench but trying to be careful not to round the edges off the head. have a firend coming round with a 1" truck impact wrench so will see if that will shift it. will let you know how it goes.

Get some heat on it. You don't need much just a little bit and it will start to come out.

Nothing holds like a good crossthread!!!:evilb:

I don't believe the rear mount (inner transom assembly) has a rubber insert. Just the bolt with a series of washers / spacers. I believe the runabout style front mounts do have a rubber insert, but can't believe any perf boat builder would use these instead of the solid cradle style.

Back to the liquid wrench, heat and the big hammer.

Saves on the Lock-tite!:lolhit:

The bushing that is pressed in the rear transom assembly does have a rubber/ fiber insert with a steel bushing. The nuts are real soft too, aluminum if I'm not mistaken. Dissimilar metals between the nut and bolt, just corroded.

Dave

Part #2 - 88791A1 --MOUNT, Rubber / 88791T This Part is No Longer Available

I follow you here but doesn't the bolt thread into the inner transom plate? Your pic looks like the bellhousing side of the equation. Isn't the rear mount bolt a shoulder bolt that threads into the inner transom plate only passing thru the rubber part? Maybe it's different on the HP transom assembly, not sure, all mine have been the HP versions.

On all of the rear engine mounts (both HP and Non) the bolt (with the washer) just goes thru the bushing on the bell housing, then the fiber washer is sandwiched between the bell housing and the inner transom assembly, then at the bottom of the inner transom, there is a cage cast in the transom assembly which the aluminum nut is housed in.

Dave

You may try to get in there with a dremel tool and cut the nut off. I'm sure it's tight, but if you can get in vertically and "slit the nut" it might loosen up. Just a thought if you are out of ideas.

We had to modify a transom assembly on my buddies boat last year because the casting had been stripped out from use of an impact gun to tighten these bolts! Follow the specs when re-installing and a little anti-sieze insn't a bad thing!

Dave

yup

Essentially where I was going, burning out the rubber mount is not going to free it up, that is not where it would be bound up and the rubber is not in the inner transom plate.

I have attempted to not visit these parts often over the years, so I'll admit my knowledge here is pretty basic. Though I have had the miss-fortune of being up close and personal with them a few times. I'd be real happy if I never have to see them again!

Without seeing it it is hard to tell what is frozen. The "bushing" is pressed into the bellhousing. Metal outer ring, rubber layer, then another metal bushing to house the bolt. Could be bound up against the bushing that is housing the bolt. Make sense?

Dave

Nah, you were right before Dave. Its the galvanic reaction of the dissimilar metals (steel bolt into an aluminum nut). Corroded-up. I like the Dremell idea, get a groove cut in that nut and it'll break open like a peanut. I've often wondered why they use aluminum nuts anyway, what's the purpose of that material choice?

Softer than the cast bellhousing. Steel nut overtightened =broken inner transom assembly.

So that they corrode all to chit, and then you break chit trying to take it apart, leading to parts sales! Parts sales is a good thing, especially when you are the only game in town.

Kinda like reactor parts, their cheap too, aren't they. :eek:

I have taken the flame wrench to them BUT would not recommend it. It was a last resort and it was getting dark out and i wanted to go home! Keep soaking for a few days and give it a wack each time with BFH (Big F__in Hammer)

Still working on it. Tried for an hour or so heating it up and used my standard impact wrench...didnt want to know. If only people have the forethought to put a little anti sieze when they put these things together. I was thinking the same about why they use different metals for the bolt and nut but i agree you dont want to wreck your transom plate if the thing siezes.

I'll keep trying but this has set me back big time..at least i understand more about how these things are put together. All the info you guys have given me is helpful so it's much appreciated.

The bolt is not turning at all? there is a little slot that the nut sits in to keep it from turning ....maybe the bolt has lossened enough to let the nut drop down out of the slot and is spinning?

Be VERY carefull with anti seize! You need to make sure you use the proper one. We often times call it always seize. If you use the allum based stuff that most stores carry it will be worse then putting it in dry. I have found that when in doubt use white lithium paste. The Merc stuff is very good as well.

The bolt is not turning at all, i've twisted a 1/2 inch extension bar already, admittedly it wasn't the toughest extension bar in the world but i've never done that before on anythnig else. I've had someone else keep an eye while i'm using the impact wrench and confirmed it isn't turning at all.

Thanks for the heads up on anti-sieze audiofn.

Cut the heads off the bolt, pull the motor off the studs. With the motors out you can get in there cut the stud right above the nut and slid the nut out of the cup.

Yeah i think that i could end up by doing that. Do you reckon grind the head off or is there another way. Not too keen on too many sparks flying around the engine bay?!

Yea I know but thats what we had to do in our 87 272 Formula. Do it slow and try to keep the heat down, If the bolts are not stuck it the bushing the motor should come out. Then you can get in there and cut the bolt just above the nut and slide the nut out of the slot.

will give it a go as last resort. It's interesting to see this has been a problem for other people as well. The front mounts are no problem cos they had stainless bolts and nuts. normal steel and aluminium is a nightmare in salt environment but i guess the most cost effective solution. most of the aluminium line support clips that hold hoses, wiring etc need replacing as they have pretty much disintegrated.

Finally i have managed to get the rear engine mount bolt out that has been giving me grief for a while now. I managed to get my hands on a Dynapack Torque multiplier, it's gotta be the best things since sliced bread!! I managed to undo the bolt intact and the head isn't chewed or anythnig...result!!

So if anyone has this problem in future...get your hands on a Torque multiplier, got to be 3/4 inch drive or bigger to cope with the torque.

Hope this thread helps others!!

when you put it back together use the brass nuts that are used to mount mercruy outboard motors(the ones that come with the engine when new) and anti seize you wont have any problem in the future and the brass nuts have more holding power:)

great thanks, will try and get hold of some.

Yeh, coz he was short on holding power!!!! :D

bet it wont get stuck again!