Topic: 1972 85 hp V4 overheated….. – Page 2 – Antique Outboard Motor Club,Inc

This topic has 15 replies, 6 voices, and was last updated 4 years, 9 months ago by amuller.

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September 29, 2020 at 4:39 am #217519
fleetwin
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US Member
The thermostat on this engine is relatively easy to get at. But, you may have to move the ignition bracket. The screws never seem to get seized into that plastic housing.. Although the “vernatherm” inside usually fails open…
OK, my mistake, the overheat occurred at low speeds, which would explain why the engine didn’t seize and paint isn’t burnt.
Am guessing you shut the engine down when the horn went off and waited for it to cool. Did you remove the engine cover, did it seem overheated?
The plastic bag/weeds theory is still a possibility…
I’m assuming the engine didn’t overheat again when you restarted it…
September 29, 2020 at 10:24 am #217535
jeff-register
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US Member
Thanks Don,
Didn’t know about the relief valves,
Jeff
September 29, 2020 at 11:47 am #217548
amuller
Participant
This discussion seems rather inconclusive. Will try to run through the sequence of events.

Motor is stock except for addition of cooling water telltale.

Had motor out for the first time since I went through it and ran for about an hour at varying speeds but only momentary full throttle.

(With the fixed idle and main jets there is not a lot to adjust other than the relationship of timer base position to throttle plates….)

Motor ran very well to my way of thinking.

Returned to ramp in 3-4 ft depth (shoaling to 2-3) at around 1500 rpm (no wake area).

Motor began to slow, looked and saw no telltale discharge, advancing throttle did not produce speed increase, motor stopped and we returned to ramp using trolling motor.

A few hours later, pulled plugs, checked compression as reported, ran on muffs with no apparent problems. Pumping normally.

So, do I assume something like the bag scenario and try another run, or dig further into motor first? Drop gearcase? Open thermostat box? Change stat?
September 29, 2020 at 3:33 pm #217552
billw
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US Member
Well the way that is worded, I would swear you ran aground…….

Long live American manufacturing!

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amuller
September 29, 2020 at 3:51 pm #217553
Bob Wight
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US Member
Based on no observed tell-tale discharge when the motor slowed down, but pump seemed to be working normally later on the muffs, I’d say you momentarily sucked up a plastic bag or some weeds. I recently had a similar experience when I sucked up some weeds while maneuvering around the dock area. Noticed temp gauge climbing so shut it down before hot alarm went off. I’d take it back out for another run and see what happens.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1955 Johnson QD-16
1957 Evinrude Fastwin 18
1957 Evinrude 3022
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

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amuller
September 29, 2020 at 10:50 pm #217565
amuller
Participant
“Well the way that is worded, I would swear you ran aground…….”

Think I have to agree. Not hard around but in some mud and maybe picking up something that blocked the intake. Live and learn. Will try another run.

Alan
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