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70hp Johnson 3 cyclinder 1994 engaging SLOW

Z

zeek

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"Hi guys ,
This is a friends

"Hi guys ,
This is a friends motor ,
Symptoms are it starts up fine , but engine wont
go over 2500 rpm , To be sure all is ok
(needed anyway) , we replaced the impeller and thermistat.

But motor wont go over 2500 for longer than 1 minute ! , If we immediately turn motor off! and then back on , we can go over 2500rm for another 30sec-minute !

Engine is NOT overheating , Im 100% sure of this !
even does this with thermistat out (only for test purposes ) and engine is very cold Same result .

the engine temperature switch has two wires comming out ,
One Tan and One white and black .


The white and black is earth (zero ohms to block). This wire connects to a tanwire(via connector) to power pack .

the Tan wire from the temp sensor Goes to wiring harnis via a connector .

If I disconnect the temp sensor tan wire !
The problem goes away !

Any help would be appreciated !! To find the fault here (diode ? horn? powerpack?)

Also If anyone has a wiring diagram for this model would be great !

Zeek
"
 
"Looks like someone has been &

"Looks like someone has been 'playing' with the colors and wires. The white/black from the temp sensor should go to white/black in powerpack. It disconnects the 'quickstart' function when engine reaches around 32 C. If connected to the brown from PP, it will initiate 'SLOW'. The tan (brown) from PP should be connected to tan from harness (alarmcircuit)."
 
"@Morten Sorry mate my mistak

"@Morten Sorry mate my mistake , I checked again

and yes the blac/white is connected to the white/black that goes to powerpack and tan from sensor goes to tan on wirring above thermistat .

if I disconnect the tan from sensor motor does "
 
"Disconnect the Tan from switc

"Disconnect the Tan from switch (not a sensor), start and test. (loaded at sea, above 2500rpm).
If everything ok, the switch AND alarmsystem is faulty, You should have an alarm!
If not ok, do as I mentioned above and 'cut' the Tan into the powerpack. If problem still there, replace powerpack. If problem gone, You may have a short somewhere in the engine harness.
Unless You are running on NGK 'R' pluggs."
 
"Thanks for reply Morten ,
ju

"Thanks for reply Morten ,
just so I get it right , "tan from switch" (thats the tan that goes to temp switch right?)

if so my preliminary tests are yes it does not go into slow mode !
And yes his alarm is not working correctly as when I earth that tan alarm only beeps once every time I touch earch and is not a constant sound.
(I think his buzzer is faulty) however when key is turned it does sound "tooee"

but when the tan is connected to the switch it goes into slow mode within 20 seconds as soon as you go above 2500rpm .

Sam"
 
"On 'one' = Yes. Disco

"On 'one' = Yes. Disconnect and test.
If ok = switch is defective. If You ground the cable from harness to switch, You should have a constant alarm as long as the cable stays grounded, or the alarmsystem is not working properly! Test the horn by grounding the tan connection - the horn should sound constant.
To get the powerpack out of SLOW the engine must be restarted, however sometimes the powerpack gets 'locked' in slow. To test that: disconnect the tan cable going into the powerpack = there should be no SLOW whatever signals the switches gives, but alarm should sound.
If You have SLOW activated without the tan cable connected to the powerpack, the powerpack must be changed. However before changing the powerpack, be sure all switches in the alarmsystem is working (temp/VRO/low-oil) and the horn or You might ruin the new powerpack as well!"
 
"Don't know if you're

"Don't know if you're still working this issue but I had exactly the same problem. No horn or light alarm but the engine would go to less than 2500RPM after about a minute. Turned out to be a water in the fuel filter problem. I determined this by squeezing the fuel bulb which caused it to run right again for another minute. After doing that about 4 times in a row, it suddenly started working OK permanaently and has ever since. Maybe you'll be that lucky. I had picked up some gas in a marina in GA which must have had water in it and the problems happened right after that."
 
"na mate your problems differe

"na mate your problems different , this motor is definately going into S.L.O.W mode , checked with timing gun and tested with different tank and hose . Also If go throught the thread youll see that if I disconect the tan from the temp switch motor runs fine .

going to check out the alarm in box (and replace ) and change temp switch .

Sam"
 
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