Merc 3.0l head gasket replacement

oGaryo

oGaryo

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well, just back from my hols in France and decided to have a look at this engine straight away.. I can't find my original thread where T'forum members were in conclusion that it was either the Head or Manifold gasket gone.. great news!! it's not the manifold gasket.. not so great news, it's definitely the Head gasket that's blown... I can see a split in it without taking the head off and there's a trickle of fluid from that point going down the side of the block.

I've changed many a car Head Gasket in the past.. is there anything to watch out for on these Merc 3.0l lumps other than the usual setting of initial timing to TDC and then adjusting with a timing light? it looks like the head can come off without removing the engine from the boat and the only complication I can think of is what's hidden behind the timing belt cover (presume it's a chain not rubber belt?)

Does anyone have a step by step guide to removing and refitting the head please? I also need to source a decent head gasket kit, any recommendations there too please?

I'd like to get this sorted asap so I can get back on the water before the UK sun runs out so am planning on sorting the gasket this weekend if I can get the parts and procedure sorted before then.

cheers Gary
 
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I think they are a push rod engine, as such, you will not have to go near the valve or ignition timing. if you are doing it yourself perhaps its worth investing in a workshop manual, if the gasket has been "blown" for some time and there is a visible leak the head may need skimming, whilst its off consider lapping the valves in and de-coking
 
thanks fellas.. have just had another look before getting some kipp and you're right, the timing's not driven off a cam sprocket like the auto engine's I'm more familiar with.. therefore, I'm presuming it's a simple case of removing peripheral gear, lifting the head and then replacing the gasket (it blew on the last trip and was run at 6knts on the broads on the way back from Breydon water.. after doing 20 to 30 knts for about 10 mins before noticing the noise and limping it back.. I doubt the head's warped as a result of that but will have it check down a place I know that can check and skim an auto head if needed, I'll check the usual once off too (valve seat, stems etc).

oh well.. yet another chance to learn more about the inner workings of a marine engine :-)
 
It's a piece of wee-wee mate.No need to lose valve or ignition timing-remove manifold, all the gubbins on top of the rocker cover, rocker cover, loosen rockers and remove pushrods, couple of hoses at the front and alternator drive belt, remove bolts and lift off.
And second Trickett marine for parts.
Have fun.
 
will hopefully be ready to do the repair at the weekend... have ordered a head gasket, manifold to head gasket and a manifold end plate gasket from Trickett today for a little under 50 notes posted. should be with me Friday ready for installing on Saturday and I'll be taking the head off tomorrow night.. only needed the manifold end plate gasket and manifold to head gasket as I'd taken them off during fault finding.

I'll be back on the water next weekend with any luck with SWMBO coming with me for a jaunt out of Lymington for the first time.... weather & waterproof makeup permitting :-)
 
Very easy to get the head off, 30-40 mins max, I have done a few of these head gaskets and they are prone to blowing between cyl 2 and 3, often the head gets burnt away where the hot gases blow out so it may need skimming. There is a special procedure for adjusting the valves as they have hydraulic lifters when reassembling, when you have got the valves for each cylinder at the correct place for adjusting you wind down the adjusting screw on the rocker until it just nips the pushrod and you can't rotate it anymore, then you go one complete turn on the screw again and its set.
While you have the carb off check the accelerator pump is working, it should spray a jet of fuel out of a small nozzle in the venturi when you open the throttle quickly, there is a oneway ball valve in the bottom of the float bowl which feeds it and these often seize closed so no fuel gets injected when accelerating.
 
thanks spannerman, good stuff.. the carb's definitely ok as I've given it a strip down a month or so ago... do you know if it's possible to take the whole rocker assembly off and then torque it back down once the head's been replaced i.e. no need to carry out individual valve gap adjustments? cheers Gary
 
Rocker arms are fitted by soaking the arm sockets and rocker ball bearing surfaces with oil, then torquing to 20 foot lbs. Each piston must be at TDC when you do this
Valve clearances are set by the hydraulic lifters automatically.


In answer to your probable next question, the head bolt torque is 90 ft lbs. Official torque tightening sequence and method is to apply a non hardening sealant to the bolt threads, tighten finger tight, then starting with middle pair torque them to 90 ft lbs, then left pair, then right pair, then far left pair, then finally far right pair :D
 
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well, how easy was that! apart from a sticky rocker cover, it all came apart with surprising ease... no head bolts shearing, no popping the head off the block using a winch and the weight of the engine.. all toooooooooooo easy, something's bound to go pear shaped when refitting :-) mind you, I received the obligatory skinned knuckle, I've yet to work on an engine without coming away with less skin than I started with ;-)

head's now off and I've found #3 Cylinder has blown on the exhaust manifold side.

thanks for the details Tinkicker.. appreciated and will defo be of use on rebuild... I set #1 cylinder to TDC before loosening off the pushrods, counting the number of turns.. have wrapped each rod in its own bag labelling the number of turns required to get the nut back to where it was and have labelled the valve it was associated with... I'll still do the settings process you've mentioned but the number of turns thing will at least get me around the mark before making the final adjustments


only one worry, there's the reminents of a large radious spring in bits (several pieces of wire) that was sitting in the base of the large water pipe from the thermostat.. something's missing a spring in the water system by the look of it, suspect it's the thermostat so I'll need to check that out.. the water channels dont look brilliant either (rust deposits) so I guess a serious flush will be in order.

will be making everything good tomorrow prior to refitting on Saturday
 
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that spring is meant to be there, think its to stop the pipe kinking or sumthing, was checking the hoses one day and gave it a sqeeze , thought it was full of pebbles lol, took it of and found the spring inside the pipe lol.
 
tinkicker0 said:
Rocker arms are fitted by soaking the arm sockets and rocker ball bearing surfaces with oil, then torquing to 20 foot lbs. Each piston must be at TDC when you do this
Valve clearances are set by the hydraulic lifters automatically.


In answer to your probable next question, the head bolt torque is 90 ft lbs. Official torque tightening sequence and method is to apply a non hardening sealant to the bolt threads, tighten finger tight, then starting with middle pair torque them to 90 ft lbs, then left pair, then right pair, then far left pair, then finally far right pair :D
Click to expand...

The ROCKERS are NOT torqued! you will set valves incorrectly. Follow Spanner mans set up as this is the correct way to set up the clearances. But i am 99.9% sure once you have lost the movement in the push rod its a 3/4 turn more to set the valve.
 
gingie said:
The ROCKERS are NOT torqued! you will set valves incorrectly. Follow Spanner mans set up as this is the correct way to set up the clearances. But i am 99.9% sure once you have lost the movement in the push rod its a 3/4 turn more to set the valve.
Click to expand...

that what it says in the service manual mate..
 
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jimmcgee said:
that spring is meant to be there, think its to stop the pipe kinking or sumthing, was checking the hoses one day and gave it a sqeeze , thought it was full of pebbles lol, took it of and found the spring inside the pipe lol.
Click to expand...


cheers mate... you'd think they'd make it from stainless steel or something.. it's rusted and broken in to several pieces
 
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Actually, the manual's a little confusing as both methods are mentioned.. one section states this:

Installation
IMPORTANT: When installing rocker arms and
rocker arm balls, coat bearing surfaces of rocker
arms and rocker arm balls with engine oil.

1. Install push rods in their original locations. Be
sure push rods seat in lifter socket.
2. Install rocker arms, rocker arm balls and rocker
arm nuts in their original locations.
3. Torque rocker arm nuts to 20 lb. ft. (27 N·m). No
valve adjustment is required. Valve lash is automatically
set when rocker arm nuts are torqued to
specification.
4. Adjust carburetor idle speed and mixture.


Then it goes on to state

Valve Adjustment
With valve cover removed, adjust valves when lifter
is on low part of camshaft lobe, as follows:

1. Crank engine with starter or turn over in normal
direction of rotation until mark on torsional damper
lines up with center “0” mark on timing tab, and
engine is in No. 1 firing position. This may be determined
by placing fingers on No. 1 valve as
mark. If valves move as mark comes up to timing
tab, engine is in No.4 firing position and should be
turned over one more time to reach No. 1 position.
50770
No. 1 Cylinder - Exhaust and Intake
No. 2 Cylinder - Intake
No. 3 Cylinder - Exhaust
No. 4 Cylinder - Intake
2. With engine in No. 1 firing position as determined
above, the following valves may be adjusted:
3. Back out adjusting nut until lash is felt at push rod,
then turn in adjusting nut until all lash is removed.
This can be determined by moving push rod upand-
down while turning adjusting nut until all play
is removed.
4. Hydraulic lifters now can be adjusted by tightening
adjustment nut an additional 3/4-turn. Valve
lash should be checked after engine
5. Crank engine one revolution until pointer “0” mark
and torsional damper mark are again in alignment.
This is No. 4 firing position. With engine in
this position, the following valves may be adjusted:
No. 2 Cylinder - Exhaust
No. 3 Cylinder - Intake
No. 4 Cylinder - Exhaust
6. Install distributor cap, spark plug wires and coil
lead.
7. Install rocker arm cover; torque to 40 lb. in. (4.5
N·m).
 
Gingie

Err My manual is the official mercruiser manual, not the Seloc one.
It says "torque rocker assembly nuts to 20 ft lbs."

There is a further procedure with the engine running if required after everything has settled down, but the official Mercruiser line is torque them on rebuild.

One other thing, the pushrods come in different lengths for lifter stroke adjustment, so do not mix em up. According to the book anyway.
 
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thanks again... I've labelled the rods to ensure they go back in the right tube so should be ok on that one. The Seloc manual also mentions the adjustment when running but warns if you get it wrong, bent rods and knackered pistons may occur so I'll be steering clear of that method I reckon ;-) cheers
 
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