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Overheat Buzzer when getting up on plane

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kiwi_dave

Contributing Member
"84 Evinrude 140 with over hea

"84 Evinrude 140 with over heating buzzer issue. I can motor around doing 6-10 knots for hours, but as soon as I give it full throttle to get it up on the plane, the overheating buzzer will go off( inside the throttle control unit), within 10-15 seconds. I can take the coweling cover off to expose the motor(which doesnt feel hot? ) and wait 10-20 minutes for the buzzer to turn off, then Im away again.
Lead up details are Ive had the boat for 3 months ( so am a bit of an outboard virgin), and prior to that, the boat had been sitting for 12-15 months without being turned over. Ive had the fuel line, tank, and carbies serviced, so it actually runs like a dream, but for the buzzer going off. I am getting a good squirt from the tell tail, and have been advised that water is circulating fine. PLEASE PLEASE can someone advise what I should be looking at.

DAve"
 
"David.... There are two (

"David.... There are two (2) thermostats in that engine, located in the housing that the hoses leading from the cylinder heads attach to. It's possible that one or both of them are sticking. When in doubt, replace both of them.

The thermostats open roughly at about 143°/148°, and the warning horn sounds off before the engine gets hot enough to do damage, hence the term "Warning" and not "Uh Oh, too bad".

However, I strongly suggest that you drop the lower unit and remove the water pump for inspection..... and if that water pump hasn't been replaced in the past few years (even if it looks okay), have a new complete water pump installed for peace of mind.

If the engine is running too cold at a low rpm, it's possible that the water pump has been failing and someone has actually removed the thermostats in a "patch work" move to compensate for the pump problem.

Another item that will cause overheating, (I know you said the engine doesn't get hot), are the water deflectors that guide the water on its specified path, explained as follows.

(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.

When time permits, visit my store at:http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store"
 
"Don't know your engine. I

"Don't know your engine. If it has pressure release valves above the thermostats (some call them poppit valves) they would be high on my list of usual suspects. They are located under the same covers as the stats, and are cheap and easy to replace. Under higher RPM's they are supposed to open to provide increased cooling."
 
"The usual cause of this ,is a

"The usual cause of this ,is a bad impeller,(water pump)..i would inst a new comp kit,and if it continues,look further.."
 
"Grrrrrr !!
I have just recd

"Grrrrrr !!
I have just recd your posting re the ACTUAL model of my donk ( engine )1978 140hp crossflow, and not a 1984 140.
My apologies Joe.... Would your above advice apply to to the 1978 140hp ? and what does cross flow mean?"
 
"David.... Yes, my above reply

"David.... Yes, my above reply would still apply.

There are quite a few differences between a "crossflow" engine and a "loop charged" engine. Keeping it simple, your engine would be a crossflow which has domed pistons and two dual throated metal carburetors which are quite visible..

The later V4 loop charged engines have flat top pistons and four plastic carburetors which are rather hidden."
 
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