1985 Evinrude 50 hp Buzzer Problem

[zamgod]

Historically (Last Season)
Stripped and rebuilt the lower unit, new gears, dogs, drive shaft, seals and impeller unit. Ran sweetly after boat launch.
Engine always flushed out with fresh water at the end of season.

Pre-Launch (Present Time)
Fitted a tachometer but it didn?t work. Replaced rectifier and tach now working.
Ran engine in tub with water up to lower exhaust outlets, above lower unit flange. Good tell-tale. Ran engine over several days for 20 minutes, good tell-tale and running smoothly.

Boat Launch
Launched boat last night; started easily then took it for a small trip in the bay. Increased speed slowly-running great! Kept it at about 6.5 mph (GPS) for about 10 minutes then increased the speed gradually. At about 8.5 mph the overheat buzzer started to sound, shut down the engine. My mate checked the cylinder head and it seemed to be cool. Started the engine and allowed her to idle, the buzzer sounded but stopped after about 30 sec. My buddy checked the tell-tale and the water was tepid.
Decide to go further afield keeping the speed to 6.5 mph and it ran like a dream for about 20 minutes. Decided to increase speed gradually at about 9 mph the buzzer started again, switched off the engine again.
Repeated the previous routine and the buzzer stopped while on idle, sailed back to port at 6.5 mph with no further incident.
Historically top speed has been in the region of 22 to 25 mph(GPS).

Anybody got any idea what my problem could be?
Thanks.

 

[EN2]

Re: 1985 Evinrude 50 hp Buzzer Problem

If your temperature is indeed within the normal range, 140 - 150 F at low speed, full throttle 120, check with infrared thermometer. I would suspect temp switch being faulty, this can also be tested.

 

[zamgod]

Re: 1985 Evinrude 50 hp Buzzer Problem

Thanks EN2.
I don't have an infrared thermom', will an electronic one do?
Is the temp switch located at the top rear of the block with a brown wire attached? Does it just pull out or do you have to remove engine bits to get it out?
While we're on the subject if I wanted to replace the thermostat at the same time, where is it lacated and is it easy to remove?
Thanks.

 

[zamgod]

Re: 1985 Evinrude 50 hp Buzzer Problem

I suppose the first thing I need to know is; how do I test the temp switch?
Thanks.

 

[EN2]

Re: 1985 Evinrude 50 hp Buzzer Problem

Let's determine engine temp first then move on to the temp switch. The thermostat is located at the bottom of the head,removing the head cover will access the thermostat. Fourteen 1/4 -20 bolts. Go easy don't break any. When the cover is removed the temp switch will pull out. The two bolts at the bottom are kind of a bear to get at but patience is key here. Make sure gasket surfaces are perfectly clean. Use some type of sealer on the gasket, no silicone. Use it on the bolts also. Try the thermometer you have and see what reading you get. If you Have the OMC sevice manual, it shows how to test the temp switch. If you don't I will get back to you later.

 

[zamgod]

Re: 1985 Evinrude 50 hp Buzzer Problem

Many thanks EN2.
A couple of days ago I went out to the mooring and ran the engine, at idle, for about 1 hour. Periodically increasing the revs to about 2000 rpm for about 15 second on the fast idle. I had no problems with the alarm sounding. So decided to take the boat out on the bay today, Sunday, and test her.
Started first kick and motored around the bay at about 5 knots for about half an hour and then gently eased her up to about 13 knots. Remained at that for about 15 min and then gently increased to maximum power, about 5500 rpm and 20 knots. I did several runs at max power for about another 15 min and still no problem with the buzzer. During this time the tell-tale was at most tepid. After about a couple of hours workout I tied up at the mooring, switched off and quickly felt the "water jacket"/head and at most it was tepid. I could leave my finger on no problem.
After lunch four of us went on a small trip to a nearby island, about 5 miles distant. No problem with the buzzer/overheating even at max power, 5500 rpm and 17 knots with four on board.
Do you reckon it had maybe been a small blockage that has cleared itself?
If I have no more problems then at the end of season I'll use your procedure to replace the thermostat and temp switch.
Many thanks for your help and advice, I wasn't quite sure where these bits were located.....now I know!

 

[EN2]

Re: 1985 Evinrude 50 hp Buzzer Problem

Going by what are experiencing right now I don't think you have an overheating problem. Could be that the tan wire has an intermittent ground somewhere. The tell tale will tell you nothing about water temp as it exits before entering the power head, it just tells you the water pump is working.

 

[zamgod]

Re: 1985 Evinrude 50 hp Buzzer Problem

Going by what are experiencing right now I don't think you have an overheating problem. Could be that the tan wire has an intermittent ground somewhere. The tell tale will tell you nothing about water temp as it exits before entering the power head, it just tells you the water pump is working.

Funny you should mention that!
That's really the only thing I did before all these tests, I moved and taped the brown wire to the loom, away from the vicinity of the spark plug. I also noticed that there were two brown wires in the loom but one had been cut. The only thing that I could think of was that it's a standard loom which fits several models, some may have two temp switches.
What do ya reckon?

 

[mark1961]

Re: 1985 Evinrude 50 hp Buzzer Problem

I also noticed that there were two brown wires in the loom but one had been cut. The only thing that I could think of was that it's a standard loom which fits several models, some may have two temp switches.
What do ya reckon?

The V4 harness has a different part number.....

Im thinking the wire is VRO related (low oil warning)...... is it still in use or are you premixing?

 

[zamgod]

Re: 1985 Evinrude 50 hp Buzzer Problem

The engine model is E50BELCOB and was indeed a VRO which I converted to pre-mix. I'd read so many different stories both here and elsewhere about the failings of VRO that I decided not to take the chance. The VRO pump is still on the engine, just the pipe is sealed. Would it be better to change over to a non-VRO dedicated pump rather than the adaptation I have?
Thanks.

 

[mark1961]

Re: 1985 Evinrude 50 hp Buzzer Problem

If you are still using the fuel side of the VRO unit as your fuel pump then yes it might pay to install a three hose pulse pump in the near future.....