In desperate times, turn to the JOC forum?

[Per]

All, I have used all sorts of boating forums to no avail.

I have a boat with a Mercury 120xr2 SportJet. An exhaust leak plus cooling water leak means manifold must come off. Two bolts sheared, but no worry once the manifold is off....

And there is the rub. It will not budge. Blowtorch along the gasket edge. Gasket remover soaking for a week. Corrosion remover in all bolt holes. Many hard whacks with a bloody great hammer. And still it will not move.

Any ideas out there?

[DaveT]

You may need to drill out the studs (knowing that you will have to weld a nut on to remove the final bit, drill down to within about 3mm from the gasket), then….

Also, using a few Stanley knife blades as wedges along the line of the gasket, tap them in gently. if you can get one blade in, try to double stack them. As you hammer them in, some blades may break so track every piece of blade and wear safety goggles.

Good luck

Dave

[Per]

Thanks Dave, good tip with the blades.

[jvcarrier]

Are you sure there in not a "hidden" bolt?

[Per]

If so it is well hidden indeed. I can see the front all around.

[thomaslk]

In terms of "corrosion remover" i made some quite good experiences with a mixture of acetone and automatic transmission fluid (about 50/50). I could free up a seized engine which was improperly stored for years. Maybe this stuff will work here as well. Costs are close to nothing - so it might be worth a trial. A kind of preload (puller/wedge/...) will be helpful as well.
good luck
Thomas

[Per]

Will try that, I had a few stanley blades and have achieved a minimal gap at one end.

[Kevin Birch]

Have a look up the exhaust pipe for any bolts, these all alloy engines have bolts every where, if it won't budge it is usually a hidden bolt. I couldn't remove a gearbox off a Yamaha engine once 5 very obvious bolts, one hidden under a sacrificial anode

Good luck.

[Per]

I found a parts catalogue online, no hidden bolts. My assumption that the block and manifold gas corroded together at the boltholes is pretty much confirmed, hammering the Stanley blades goes fine where there is only gasket material. Once it hit the area of a bolt hole the going is much tougher. So poyring acetone and ATF into boltholses and the tiny gaps achieved is the order of the day.

[Grant]

If you have all the bolts out Per apart from the sheared ones..have the sheared ones left the long part of the bolt still protruding from the block and into the manifold, or, did they shear down by the block?..if they are still long then they will probably be the cause of holding the manifold rigid, can you not use some old hard oak and make some wedges to knock in between the block and manifold, maybe using 4 of them and tapping them in on each of the 4 face/sides gradually and evenly causing it to prise off bit by bit?..Bloody salt water wrecks these engines in the end doesn't it..I think that would be the way I would try..I bet when you get it off it will be a salt corrosion issue in there..All these things are sent to try us Per ..Good luck with it sport

[Per]

Cheers Grant, they snapped 3 and 8mm below the surface respectively. More than enough to hold but b****y difficult to reach for drilling in a safe way without pulling the engine. And of course one of the nuts holding the block in place is of obscured by the manifold and nearly impossible to get at when in the boat with manifold in place.

So here is the plan: Lots of heat repeatedly applied at the manifold where the two broken bolts sit. I have poured ATF everywhere there is a crack, and into all boltholes.

Next time (this is at the summer house), I will bring acetone and pour more acetone/ATF mix every day that I am there. And I will buy some cheap knives and grind to a double edge with a flat in between. Then drive those in where the Stanley blades have made a crack. In the end the should do the trick. The way I am doing it there nay be a bit of damage to the manifold flange so Alutite and machining will probably be necessary.

Saltwater cooled engines are a bad idea indeed. I believe the power head started life as an outboard design. As it quite a few years old of course finding a replacement that drops straight in is not on. It is a real fun boat though so I am loath to give it up.

[Mark1Stu]

This may not help.....

My old school mechanic (now retired) did his apprenticeship with British Leyland. He told me how on Triumph Stags, they undid all the cylinder head bolts, attached an engine hoist to the head, and lifted the front of the car (transferring much or all of the weight to the hoist....I can't remember which) then left the car overnight. Next morning, the cylinder head had invariably separated.

I'm not suggesting this was official BL practice, but.....

[Chris_R]

It wasn't. The Stag engine has 5 bolts that are perpendicular to the block face on the exhaust side and 5 studs that go at an angle into the inlet side side of the block face. You are supposed to remove the bolts and the studs to lift the head off but typically the studs seize in the head. Stud removal tools generally aren't successful in these cases. If it works, the rope suspension method may lift the head about an inch, probably bending the studs in the process. The last time I removed the heads we had to put a plate under the lip of the head over the inside of the "V" and use a bottle jack to push the head off (and destroy the studs in the process).

[Per]

My local Jag specialist told me they used that trick on V12s at the main dealer he worked at in younger days. Problem is the manifold is on the side of the engine in my case and the side of the boat is in the way. But the wedge formed at one end by double/triple layer of Stanley blades should excert some force, and when adding knife blades later even more so. In the end this may turn out to be a case of "when an irresitistible force meets an immovable object ......"

[DaveT]

Don’t forget to remove the blades and tap the manifold back on every so often, eventually something will give way, hopefully not the manifold in more than one piece!

Dave