WOT Overheat 94 ProV 115hp

[Jason2tpa]

The process of pulling off the head covers is very simple, assuming you don't have to mess with a stripped head bolt. While in you're in there, give a good look at the head cover gasket and head gasket. They might be eroded to paper thin or nothing.

Some bolts in and around the engine that require a small amount of torque you can get away with not using a torque wrench. But using a torque wrench is an absolute necessity for reinstalling head bolts, fyi.

If after installing new stats you still experience the same overheat issue, consider running a Salt-X treatment through the engine before pulling off head covers. This stuff definitely helps to breakup and soften up the rock hard corrosion in the water passages. There are other brand name products that do the same thing, Salt X is the one I've used in the past with success. Good luck.

[KlinkSanford]

Finally had the time to work on it. Removed the port thermostat housing and found enough corrosion to warrant going further. Removed the cylinder head cover and this is how I found the outside of the cylinder head. Needs a good cleaning.

http://s1203.photobucket.com/user/pm...tml?sort=3&o=0

The cylinder head cover and the water passages around the cylinders were not so bad, I've seen them totally clogged on my Johnson's. Still need cleaning.

All the bolts came off without a hitch. Will wire brush all the bolt threads and re-install everything as soon as I get the gaskets.

Same results on the for the starboard head.

Tested the thermostats and they work fine.

[pstephens46]

Was there a pic here somewhere?

[KlinkSanford]

I can't get the picture to download here. It is at photobucket url Cyl Head Port.jpg Photo by pmbaker1975 | Photobucket

[cpostis]

I see a couple of spots that look like may be completely blocked.

Anyway, you may wish to pull your exhaust plate cover and exhaust plate. The water side of mine had excess deposits. If you do, you'll have to replace the two gaskets. The exhaust side and had somewhat of carbon built up. While I had the plate off, I checked for carbon build up in the block past the exhaust ports. Cleaned it all up.
Now be aware, the 6mm bolts for the exhaust plate cover are the ones where I broke six that I mentioned earlier.

Here's the area I'm talking about for your motor:

[IMG]P115.ExhaustPlate by Charles Postis, on Flickr[/IMG]

[KlinkSanford]

Cleaning Heads with Citric Acid

I quickly (10 minutes each ) cleaned both heads by hand to get the big crud off with scraping devices (picks and screwdrivers), amazing that the engine could run with all that crud. Then placed the port cylinder head flat on a disposable aluminum turkey tray and filled with citric acid mix (as per instructions above) and put in the oven to bake at at 240 degrees. The water just raises little bubbles on bottom of the tray and then they rise to the surface one here one there, an indication of proper temperature, (you don't want an absolute rolling boil). I used the oven and the tray because the part was too big for the stove top, and would need gallons of citric acid with the part standing up. I only did the port head to test the method.

I kept checking the progress and adding more time, remember, this is a really crud up head. It took 4 hours. I then took the pan out and put it on the counter top, and took off with a skewer stick, razor blade and SS wool, all that was left on (crud and gasket, it was all soft. The long 4 hour soak left a film on the exterior paint, like a white haze, it is residue from the cleaning, like a black film from the "melted" corrosion. This has happened before, and it is easily removed with fresh citric acid and a toothbrush, soap won't do it. I should have done this second cleaning right away without letting the stuff dry. Normally it does not matter when you do it, but in this case it was really a dirty job and the citric acid was full of the dirt. I threw away the old citric acid. Pictures are before, after 10 minute scraping, and after citric acid bath.

[KlinkSanford]

I cleaned all the water passages on the cylinder block, cleaned the piston tops of carbon, cleaned all gasket surfaces put everything back together with new head gaskets, cover gaskets, thermostat gaskets, the 4 little zincs, and cleaned machine screws, and female threads. Will be testing it tomorrow weather permitting.

[KlinkSanford]

Finally had the time to test the boat. It runs 20 degrees cooler and the water pressure (I installed new impeller) increased from 5 -15lbs to now 10-25lbs (800 rpms to WOT)

[TownsendsFJR1300]

And now NO overheat alarms as well?

Pic's were amazing BTW...

[Jason2tpa]

Great news! Your hard work paid off, literally. A marine mechanics labor fee for that job would have probably topped $500.

[KlinkSanford]

And now NO overheat alarms as well?

Pic's were amazing BTW...

I ran it at WOT for 5 minutes and water the temp remained unchanged. No alarm. Before the cleaning, the alarm went off within 15 seconds at WOT, though it could run all day at 3400-3800.

[KlinkSanford]

What do you think of 25lbs of water pressure at WOT? Is that high for this engine?

[rodbolt17]

I use bullit point type drill bits.
once started they wont walk.
they are expensive and cannot be resharpened like a conventional bit but they work very well.
it is also why I charge 100 bucks a hole to drill and tap or heli-coil.

[TownsendsFJR1300]

Great news! Your hard work paid off, literally. A marine mechanics labor fee for that job would have probably topped $500.

For my neighbors 200, they wanted $800.00 plus parts to do the job...

That sealed the deal, we were doing it and it wasn't hard to do..

[TownsendsFJR1300]

What do you think of 25lbs of water pressure at WOT? Is that high for this engine?

Fantastic, sounds fixed to me!!!

Your pressure control valve (PCV) will open up if it's too much pressure- your good!!