Inspection cover leak 1984 470

[shiloh87]

My daughter and I launched the boat for the very first time today, and ran into a snag.
As mentioned in previous post I restored/rebuilt my 1984 470. While test running it on the stand, I noticed that it was weeping oil from around the lifter inspection cover under the intake manifold, so I removed the cover, gasket maker silicon was applied to both sides of a new gasket and re-installed. While out and about in the boat today it started leaking again, dumped about 2 litres before getting back to dock.
How in blazes are you supposed to seal this cover. To me its a pi$$ poor design, it`s as long as the block and only 4 bolts run the length down the center. No real way to torque them(15-20 ft/lbs) without distorting it, ie pulling the center in which probably opens the sides and ends.
Now out to clean the mess out of the bilge.
Any help or thoughts greatly appreciated.

 

[GA_Boater]

The cover is probably warped out of shape from previous attempts to stop a leak. The same design has been used on millions of motors that keep the oil where it belongs, including 470's.

 

[Captain Greg]

I agree with GA replace the cover

 

[shiloh87]

Ok I`ll look for a replacement....

 

[achris]

No longer available new. Here's the part number so you can chase down a second hand one.

41505A1

Here's one I found quite quickly. (I know it says 488. 470, 485 and 488 share the engine block, head and everything else expect intake and exhaust manifold and carb)

MerCruiser 488 Side Cover P/N 41505A1 - NLA | eBay

We carry thousands of quality products for all your boating needs.

www.ebay.com

 

[Scott Danforth]

About 25 million 4 cylinder and 6 cylinder inline motors built from about 1930 to the 1990s had lifter covers like the 470. Nearly all only have only 4 fasteners

 

[shiloh87]

Thanks for the link, but I`m in Canada, shipping from the States if they`ll ship usually costs as much or more then the items worth.
Lots of odds and ends up here, I`ll be looking for sure.
Will have to make a gasket, used my spare and there seems to be none available unless I pay nearly $300 for a chinese made gasket kit, and that aint happening.
Going to go get a role of 1/8" felpro cork today and see if I can duplicate the gasket.

 

[achris]

... there seems to be none available unless I pay nearly $300 for a chinese made gasket kit, and that aint happening.

Nope. Still available from Merc, and 'only' $87.

Mercury-Mercruiser 27-72479A5 GASKET

Mercury-Mercruiser 27-72479A5 GASKET genuine factory part not aftermarket. Fast shipping - Click here to see live inventory status

www.mercruiserparts.com

Chris.........

 

[Scott Danforth]

Merc borrowed from the GM inliner motors. May want to check to see if the lifter cover gasket is same from a 1962 chevy 153 or. Get one from a 196/230/250 and cut down

 

[shiloh87]

Good tip thanx, will look into that.

 

[achris]

Merc borrowed from the GM inliner motors. May want to check to see if the lifter cover gasket is same from a 1962 chevy 153 or. Get one from a 196/230/250 and cut down

The covers on the 470 is cast Ali. The ones on the GM engines were pressed tin... Gasket was also different.

 

[Captain Greg]

is it possible to make yourself a cork gasket for it that may do the job

 

[Eric 3.7LX Alpha 1]

You can do a search for Mahle # PS33264 for the gasket. It looks like it's backordered a bit but you can get just that one gasket.

 

[shiloh87]

"is it possible to make yourself a cork gasket for it that may do the job"

Yes it is possible, I bought a role of felpro 1/8" cork/rubber and managed to make a successful gasket, careful measuring and cutting, fits perfect and only cost $6.50.
Here`s what I`ve learned, the bolts for this cover is to be torqued to 15 ft/lbs, based on manual #3, which cover my engine. You could never torque it to that before the cover would crack, and I`ll say it again, bad design, even snugging it up a bit too much will split the gasket causing it to leak. So my plan is to finger tighten then snug up a bit just feeling the gasket compress a bit, with lock tite blue on the threads, in theory this should work.
The very nature as to how the 2 surfaces mate will shear/split the gasket in the middle length wise if tightened to much, its more of a feel kind of thing.
Once installed hopefully good enough to not leak, then its fixed until next tear down. If not and it needs to be tightened more to stop a leak, that in its self could more than likely damage the gasket causing it to leak, so fingers crossed, will be installing tomorrow and testing on the weekend.

 

[shiloh87]

Decided not to buy a used cover, odds are they`d all be distorted, not wasting money that way.
I replaced the cover with one I made from 1/2" aircraft grade aluminum, machined it to fit properly, distributor notch, bolt hole recess for o-ring seals. This does not flex or distort at all, simple gasket, just a solid rectangle, finger tightened the bolts and then snugged enough to just feel the gasket compress a bit.
Should know this week-end if it leaks or not, fingers X`ed.

 

[shiloh87]

Ran the engine for a bit yesterday on the trailer, no signs of leaks, back in the water tomorrow weather permitting.

 

[shiloh87]

Well I believe I`ve got this licked, wife and I were out this morning for an hr, no leaks.
Due to the bays temp, 9deg C, the engine temp never went above 125deg, is that ok, manual says 140-160 is normal operating temp.

cheers

 

[GA_Boater]

Due to the bays temp, 9deg C, the engine temp never went above 125deg, is that ok, manual says 140-160 is normal operating temp.

cheers

Then you have a bad thermostat.

 

[Eric 3.7LX Alpha 1]

or an inaccurate temp gauge or bad sender. Mr. Gasket makes a radiator cap with built in mechanical temp gauge built in you can use to confirm your helm gauge.

 

[shiloh87]

Gauges are all brand new Faria, To be safe I`m going to order new thermostat and sender, both were original to the engine and looked OK, but I guess not, small investment to be sure.
The Mr Gasket cap sounds like a good investment for peace of mind as well, thanx for the tip,
Cheers