1984 Mercruiser 260 head gasket job, lots of pics and questions!

[akorcovelos]

So I bought a 1984 21' Webbcraft Riviera with a Merc 260 5.7l yesterday from a family "friend" who told me the boat was mechanically perfect, engine ran strong, 2 year old out drive, winterized it every year, blah blah...He started it on the muffs in his driveway and it sounded good, and shifted into forward/reverse good. This is my first I/O so as far as knew it was good to go, and he told me it was ready to go out and enjoy on the water.

wrong...

I got it home and checked the oil, wasn't even showing on the dipstick. ok, top it off with Mercruiser oil he gave me with the boat. Put it in the water and it starts up, idles good. I get out of our channel and go to take off, and the boat won't even get up on plain, just falls on its face when I put it under any load. Bring it back to the dock and start looking at the engine and I see water dripping from both manifolds. Port manifold has a good sized crack in the bottom, and the starboard has a petcock in the bottom plug that the valve was missing from allowing water to just pour out.

Here are a couple pics:

starboard manifold

port manifold

So I pull the boat out and get it home, and immediately do a compression check on the engine, readings are:

1 - 150psi
2 - 150psi
3 - 100psi
4 - 150psi
5 - 90psi
6 - 130psi
7 - 120psi
8 - 130psi

from my research I'm at least looking at replacing all the manifolds and risers, right?

what else am I getting myself into?

 

[Bondo]

Re: 1984 Mercruiser 260 cracked manifold, no power

Re: 1984 Mercruiser 260 cracked manifold, no power

from my research I'm at least looking at replacing all the manifolds and risers, right?

what else am I getting myself into?

Ayuh,... 'n probably a new motor dependin' on Why #5 is only 90 psi...

If it's a valve issue, maybe just a Head Rebuild...

 

[akorcovelos]

Re: 1984 Mercruiser 260 cracked manifold, no power

Re: 1984 Mercruiser 260 cracked manifold, no power

So I guess a wet compression test on those two cylinders is in order?

Even with low readings on those cylinders is there a chance I could get away with just replacing the manifolds and running it for the summer? I'm not familiar with the marine application of the GM 5.7, but I am pretty familiar with the automotive version, is there a diagram of the cooling system and heads of this engine?

 

[achris]

Re: 1984 Mercruiser 260 cracked manifold, no power

Re: 1984 Mercruiser 260 cracked manifold, no power

... is there a diagram of the cooling system and heads of this engine?

https://docs.google.com/open?id=0B1TAvwZ3Tjhfdk9PRXBWWExTU084dXpoTUhqRk9vZw

Download and save... Section 7 is the cooling system. At the end of the section there are water flow diagrams...

 

[akorcovelos]

Re: 1984 Mercruiser 260 cracked manifold, no power

Re: 1984 Mercruiser 260 cracked manifold, no power

Thanks!

assuming I need to replace the entire engine, will a 260 from any year drop in, or does it need to be a '78-'84 model?

Is upgrading to a 7.4 a drop in option, or requires tons of fabrication?

Thanks

 

[akorcovelos]

Re: 1984 Mercruiser 260 cracked manifold, no power

Re: 1984 Mercruiser 260 cracked manifold, no power

Well, I talked with a Mercruiser mechanic about my situation, and he is very confident the head gasket is blown between cylinders 3 & 5. I'm going to pull the head this weekend and see what the damage is. He told me if I'm lucky the damage is limited to the gasket and head, but if the engine got to hot he said its not uncommon for a hole to burn right through the block between those cylinders. I am really hoping its just the head...He also told me if I grind out the crack on the port manifold and get it perfectly clean it can be JB Welded and reused, has anyone else heard of doing this?

Any words of wisdom before I tear into it this weekend?

 

[achris]

Re: 1984 Mercruiser 260 cracked manifold, no power

Re: 1984 Mercruiser 260 cracked manifold, no power

...Any words of wisdom before I tear into it this weekend?

Be observant as you disassemble.. Many people just hoe into a job and miss some subtle clues as to what's happened. You will learn as much while pulling it down as you will as you 'investigate'...

Oh, and take lots of photos...

Chris.....

 

[Scott Danforth]

Re: 1984 Mercruiser 260 cracked manifold, no power

Re: 1984 Mercruiser 260 cracked manifold, no power

look for evidence of rust in the exhaust ports. this would indicate that the manifolds are leaking into the engine.

yes, you can swap other engines in place of your 79-85 block. however depending on what you look at, you may need a new flywheel, coupler, or other items.

yes, you can swap to a 7.4 liter, however the limitation may be your drive. you did not state which drive you have.

 

[akorcovelos]

Re: 1984 Mercruiser 260 cracked manifold, no power

Re: 1984 Mercruiser 260 cracked manifold, no power

I will definitely take lots of pics. I will keep an eye out for rust in the exhaust ports, but if it were leaking into the engine wouldn't I have seen signs of that when I did the compression test? The plugs were all dry and no water came out of the cylinders.

I just rebuilt the 5.7 in my Chevelle last year, would the rebuild manual I have from that apply to this engine minus the cooling system?

I'm really hoping I just have a head gasket job on my hands and not a complete engine replacement, but if i do the mechanic I talked too said he can get me a reman'd long block for around $1800 so I'll likely just do that.

The drive is a 2 year old SE106 Alpha 1 replacement, so from my research its only good to 300hp, not much more than the 265hp the 5.7 is rated at.

Here are a few pics of the boat so you all can see what I'm working with.

back before the PO ruined the engine...

Thanks for all the help!

 

[akorcovelos]

Re: 1984 Mercruiser 260 cracked manifold, no power

Re: 1984 Mercruiser 260 cracked manifold, no power

ok, maybe a stupid question but I'll ask anyway. I'm pulling the starboard head off this weekend to see if the block is damaged. If the damage is just the gasket and maybe the head, do I need to pull the port head as well or can I just fix the one thats the problem? The port side (even cylinders) all show great compression, so can I leave it on and just fix the starboard side (odd cylinders)?

 

[achris]

Re: 1984 Mercruiser 260 cracked manifold, no power

Re: 1984 Mercruiser 260 cracked manifold, no power

I guess you could do just the one side, but I'd do both... It's only another few bolts and a couple more gaskets, and while you have it down that far, would almost be silly not to..

Chris.....

 

[akorcovelos]

Re: 1984 Mercruiser 260 cracked manifold, no power

Re: 1984 Mercruiser 260 cracked manifold, no power

ok, tore the engine down today and have lots of pics and some questions for all you Mercruiser masters. First the pics.

can someone post the manual for this engine based on these serial numbers?

 

[akorcovelos]

Re: 1984 Mercruiser 260 cracked manifold, no power

Re: 1984 Mercruiser 260 cracked manifold, no power

 

[akorcovelos]

Re: 1984 Mercruiser 260 cracked manifold, no power

Re: 1984 Mercruiser 260 cracked manifold, no power

 

[akorcovelos]

Re: 1984 Mercruiser 260 cracked manifold, no power

Re: 1984 Mercruiser 260 cracked manifold, no power

 

[akorcovelos]

Re: 1984 Mercruiser 260 cracked manifold, no power

Re: 1984 Mercruiser 260 cracked manifold, no power

 

[akorcovelos]

Re: 1984 Mercruiser 260 cracked manifold, no power

Re: 1984 Mercruiser 260 cracked manifold, no power

 

[akorcovelos]

Re: 1984 Mercruiser 260 cracked manifold, no power

Re: 1984 Mercruiser 260 cracked manifold, no power

so thats where we finished up today. The heads are off to the machine shop to be pressure tested, and checked for flatness. From visible inspection it looks like the head isn't damaged, but the inside 2 cylinder exhaust valves got really hot, so maybe they warped causing the loss of compression. Hopefully it just needs a valve job.

As can be seen, both manifolds are badly cracked so I'll be ordering new ones tonight. Can I reuse the risers?

The push rods look like they all got really hot at some point, should they all be replaced? The tappets look perfect on both the cup side and the cam follower side.

Obviously there was water in the oil, as can bee seen in the pics of the inside of the valve covers and intake valley. Anything I need to worry about? We cleaned it all up real good and sprayed with penetrating oil to protect it until the heads are done.

Here is my list of replacement parts I need. Let me know if I missed something.

push rods
oil pressure sender
coil
distributor gasket
spark plugs
exhaust manifolds
coolant temp sensor
black rtv
valve cover gaskets
intake manifold gasket
head gaskets
thermostat housing gasket
140* thermostat
oil/water separator filter
oil change materials

I'm going to order parts later tonight or tomorrow, so let me know if I missed something. How long does iBoat usually take for shipping? If I order tomorrow should I have the parts by the weekend?

 

[akorcovelos]

Re: 1984 Mercruiser 260 cracked manifold, no power

Re: 1984 Mercruiser 260 cracked manifold, no power

Looking for best deals on parts, I think this is what I need. I'll be ordering 2, should have them by Thursday.

http://www.ebay.com/itm/MerCruiser-...-87114-86024-1983-2002-New-/280890774481#shId

Will this top end gasket kit work for my 260?
http://www.go2marine.com/product/82...edium=productfeed&utm_campaign=googleshopping

 

[akorcovelos]

Re: 1984 Mercruiser 260 head gasket job, lots of pics and questions!

Bump...

Ordered the manifolds last night, but still not sure about that top end gasket set, anyone?