1977 500/50 water in #4 cyl questions

[rjb75]

Like the title says-water in the #4 cyl. Engine still runs but obviously not well. It cranks freely with all spark plugs pulled so I'm hoping it's just the lower seals and I can get away cheap. What are the odds that the seals are the culprit since the other three cylinders are dry/normal?

Also, I can get a good complete powerhead from a '75 500-will this work as a drop-in?

EDIT: my serial # is 4805706

 

[JDusza]

Re: 1977 500/50 water in #4 cyl questions

Odds are not good only since there are many parts involved. Bad lower bearing, et al., bad power head to exhaust gaskets, on the block or at the transition to exhaust housing. Bad exhaust baffling gaskets.
Either way, pulling the power head and disassembling is in order.
Replacing the power head will give you someone else's problems....
J

 

[emckelvy]

Re: 1977 500/50 water in #4 cyl questions

Once the powerhead is pulled, you'll be able to inspect the bottom of the exhaust area. You'll know right away if water has been spraying into the exhaust ports of #4 cylinder, 'cause all the carbon deposits in that area will be washed clean.

When you remove the lower bearing cap, if the seals are bad it'll be very obvious. At that time you should be able to determine the best course of action for repairs.

One thought, hopefully it hasn't sat for long with water in the lower portions, otherwise you'll be replacing the crankshaft lower ball bearing, which is a job that'll require the crankcase to be split, since the bearing is pressed onto the shaft and there's no way to get at the bearing otherwise.

HTH & G'luck........ed

 

[rjb75]

Re: 1977 500/50 water in #4 cyl questions

Thanks for the replies. I don't think this has been going on for long since I changed the plugs to start the season and the #4 plug looked like all the rest with some wear and deposits. I discovered there was a problem when I had a loss of power after cruising around on the lake for 20 mins last weekend. Another plus is that, at least for the two years I've owned it, it has only been in fresh water. I'm just hoping that the rings and pistons are ok since I can't really afford to do a full powerhead rebuild right now. I will do a compression test to before I take it apart and keep my fingers crossed.

 

[rjb75]

Re: 1977 500/50 water in #4 cyl questions

Here's the update:

Cyl 1 140 psi
Cyl 2 140 psi
Cyl 3 120 psi
Cyl 4 120 psi







As you can see in the pics, lots of frothy oil all over the place. The question I have is, with those compression #s and the oil everywhere, should I just not bother trying to change the lower seals? Am I looking at a full rebuild?

 

[rjb75]

Re: 1977 500/50 water in #4 cyl questions

A couple more pics:

 

[rjb75]

Re: 1977 500/50 water in #4 cyl questions

Any opinions on how far I need to go with this-full rebuild or replace all gaskets and seals and run it?

Thanks

 

[emckelvy]

Re: 1977 500/50 water in #4 cyl questions

Maybe it's been spraying in the 2 bottom cylinders for a while. You could remove the intake port covers, that'll give you a good peek at pistons & rings on that side, to see if there's any scuffing or other damage.

If the bolts will easily come out of the exhaust manifold, I'd take it apart and get the view from the exhaust side. The exhaust side runs much hotter and takes the brunt of any abuse, so more likely you'd see ring and piston problems from there.

Even if you didn't end up tearing down the powerhead for rebuild, you'd have to replace the exh. manifold gaskets and check the baffle for perforations. Use lots of heat if the bolts won't come out. As a last resort, it's better to drill out the bolt heads rather than breaking bolts.

When you get the covers off, you'll have a "stub" of a bolt to grab with Vise Grips, and you can get direct heat & penetrant on the bolt.

Usually that'll get 'er done. Worst case, drill out the bolt completely and Heli-Coil repair the threads. Most reliable repair for an aluminum block.

HTH...........ed

 

[rjb75]

Re: 1977 500/50 water in #4 cyl questions

Is it possible to remove and reinstall the lower cap without splitting the crankcase?

 

[emckelvy]

Re: 1977 500/50 water in #4 cyl questions

Is it possible to remove and reinstall the lower cap without splitting the crankcase?

Yes, in fact there usually are tapped holes in the cap which can be used with a puller. If not, you'll have to be extremely careful if you plan on prying on the "ears" of the end cap. Very easy to break.

Use a thin putty knife or paint scraper, once you've got it away from the block you can get other appropriate "prying tools" and very gently pry a little on each ear, progressively and equally, until it comes out all the way.

Lots easier with the puller holes!

G'luck.........ed

 

[rjb75]

Re: 1977 500/50 water in #4 cyl questions

I didn't notice any tapped holes but as you can see, the cap isn't exactly clean. I'll be disassembling this sometime this weekend and I'll update with more pics. Thanks for all the info.

 

[rjb75]

Re: 1977 500/50 water in #4 cyl questions

Finally got around to removing the exhaust and transfer port covers this morning...it isn't pretty. The baffle plate has a hole and a crack in it which is where the water was coming from. The bottom two pistons are scored up pretty badly when viewed through the ports, so it's rebuild time.

Does anyone know of a good marine outboard machine shop in the northern NJ/southern NY state area that can clean/check and bore the block if necessary? I'm not looking for some cheap-o job but don't want to take it to one of the local marinas and get charged obnoxious amounts of money.