73 135 hp Opening a can of worms

[brynifer]

Running over 3500 rpm will cause the motor to overheat within a few minutes, Pump and thermostat are good. I also notice that of the two outlet holes behind the motor, one does not throw quite as much water when the thermostat opens, no obvious clogs that I can see. I would really like to pull the heads and exhaust cover to give it a good cleaning, however, due to it's age, i am reluctant to because I can see myself breaking bolts or rounding off the heads of them, creating nothing but more problems.
I have read a few posts which suggest that running vinegar through the block will clean out salt deposits. My thought is to remove the two rubber hoses which feed water to the block and manually pump vinegar into the block.
Any thoughts on this vinegar idea? My only thought is, if either the vinegar or my taking wrenches to it "F's" it up, I'll have an excuse to repower the boat.

 

[Joe Reeves]

Re: 73 135 hp Opening a can of worms

Forget the vinegar theory.... where do these ideas come from? (grin).

If you installed a complete water pump assembly (not just an impeller) and new thermostats, and you're sure you did the job properly, that leaves the head gaskets and water deflectors.

Use a hand held propane torch to heat the aluminum around the head bolts to help free them. There are no short cuts.

(Water Deflectors)
(J. Reeves)

Water deflectors are actually lengths of 3/8" outside diameter rubber hose, installed between the top cylinder and any cylinder beneath it, and also between the bottom cylinder and the block. The purpose of the deflectors is to have the water follow a definite path around the cylinder walls. Unfortunately the deflectors between the cylinders will at times swell sideways due to either a previous bad overheating problem, or simply due to age and salt corrosion. This causes a water flow restriction which usually allows the water to cool sufficently at low rpms but not at the higher rpms.

This hose material can be purchased reasonably at any automotive parts type store if you care to make your own, or you can purchase individual deflectors at any Evinrude/Johnson dealership at a somewhat higher cost.

Removing and installing them can be a hassle at times, but not always. I use a sharply pointed scribe with about 1/4" of the tip bent at a right angle whereas I can reach in, jab the tip sideways into the rubber, then yank it out. It's necessary to clean the seating surfaces where the ruber contacts the block with a small rat tail file to eliminate salt deposits etc. When installing the new rubber deflector, coat the deflector and the metal surfaces with WD40 which will act as lubrication to allow it to go in as easily as possible.

Make sure that you insert something into that deflector area before cutting and installing the deflectors if you make your own so that you will be certain that they are the right length and also that they will be seated properly. Usually a very small amount will be left extending about the block sealing area..... simply cut the excess off with a single edge razor blade.

 

[emdsapmgr]

Re: 73 135 hp Opening a can of worms

You can pull the head covers off the heads. Once you get them off, visually check for any restrictons in the head water coolant passages. Water flow restrictions, such as weeds, sand and salt deposits can cause overheating. What you find inside the heads will be similar to what you find inside the block.

 

[brynifer]

Re: 73 135 hp Opening a can of worms

yeah, i had an idea the vinegar was too easy to be real. Those deflector hoses sound like an after-thought as a result of a design defect. Seems dumb to but rubber hoses inside an engine block. Guess I'll be breaking out the torch and wrenches.
Thank you for the help guys