Johnson 70 HP Slow Mode 1998

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5forfighting

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I have a 1998 Johnson 70 HP (4 cylinder, 4 stroke) Outboard that is experiencing symptoms that sounmd like Slow Mode. I have not yet had it on the water. Previous owner, is a person I can trust and claims that the motor ran perfectly 2 years ago. I changed gasoline and added Sea Form. The motor starts up great and runs well untill I hit approximately 2500 RPM. There are no Red Lights lit when this happens and I know that all lights work because they cycle on and then off during initial Key on. All of my testing has all been done with the Ear Muffs on. Water Pump seems fine - there is a steady stream of very warm water pissing out the indication hole.
 

daselbee

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Re: Johnson 70 HP Slow Mode 1998

You have a Suzuki DF-70 that is branded as a Johnson.
You describe in some detail what you have done, and up to 2500 rpm....then you stop all detail.

What the heck happens at 2500????

Please post model number too. I have guessed it to be J70FLTLECS. Right?
 

daselbee

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Re: Johnson 70 HP Slow Mode 1998

Is it surging....fast...slow....fast...slow....if so that is the rev limiter.

The engine thinks it is still in neutral, even tho you have it is gear...
There is a switch on the throttle linkage on the stbd side, below the level of the side cover. You have to take the side cover off.
It is kinda below the oil filter.

It is probably stuck closed. I will check my manual regarding the closed-open question.....can't remember which way the switch is when the gearshift mechanism is in neutral....but if the engine thinks it is still in neutral, the rev limiter kicks in.
 

5forfighting

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Re: Johnson 70 HP Slow Mode 1998

Is it surging....fast...slow....fast...slow....if so that is the rev limiter.

The engine thinks it is still in neutral, even tho you have it is gear...
There is a switch on the throttle linkage on the stbd side, below the level of the side cover. You have to take the side cover off.
It is kinda below the oil filter.

It is probably stuck closed. I will check my manual regarding the closed-open question.....can't remember which way the switch is when the gearshift mechanism is in neutral....but if the engine thinks it is still in neutral, the rev limiter kicks in.

Yes, I think that you are correct. I have been doing this in Nuetral with ear muffs on. Do you think that if I do this in the water and in gear, there is a chance that the rev limiter will not kick in? Thanks.
 

5forfighting

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Re: Johnson 70 HP Slow Mode 1998

You have a Suzuki DF-70 that is branded as a Johnson.
You describe in some detail what you have done, and up to 2500 rpm....then you stop all detail.

What the heck happens at 2500????

Please post model number too. I have guessed it to be J70FLTLECS. Right?

It acts like a Rev Limiter has kicked in, other wise known as "Slow Mode".
My Model Number is J70FTLEC
 

5forfighting

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Re: Johnson 70 HP Slow Mode 1998

The switch appears, visually to be working. When I trottle up without holding neutral, the switch button extends. It also seems to be extended fully. I will try to do an electrical check next to make sure that it changes state.
 

daselbee

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Re: Johnson 70 HP Slow Mode 1998

If you are revving the throttle manually, leaving the engine in neutral, i.e. the lever on the gearshift linkage still has the switch depressed, then YES that is normal operation. The EMM will not allow the engine to rev past 2500 when in neutral.

I wouldn't call that SLOW mode tho.
 

5forfighting

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Re: Johnson 70 HP Slow Mode 1998

I just checked the continuity of the switch. It changes state when I shift into gear. I would assume that it is working.
Another thing that happened: While testing with the ear muffs, I put the outdrive in neutral and ran the engine at about 2000 RPM. The engine overheated (Hot light on). I idled for 2 minutes but the light did not turn. I turned off the engine a wait about 30 minutes. When I started it back up, the all lights cycled normally and the Hot light was now off. I took off the thermostat and tested in boiling water. It opens. I did not check the exact temp of the water. I also checked the impeller and found it looking like brand new. Because most lakes here in Michigan are still frozen and the Detroit River is still full of ice flows, my next test will be to full a large bin with water and test the outdrive while submerged. After the other testing that I have done, I'm not confident that this will learn anything from this. Any more suggestions/ideas? Please...
 

daselbee

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Re: Johnson 70 HP Slow Mode 1998

I have found that muffs introduce air into the water flow/supply. This can form air pockets inside the engine, head, etc.
I always use a tank. The only exception is when I have the LU off, I connect a hose directly to the water tube and run it that way.

Be aware of the pop-off valve located in the side of the exhaust manifold at the top. It is very close in proximity to the thermostat.
At higher RPMs that valve blows open, allowing more water flow. Follow those large hoses (one connects to the thermo); there is one that goes into the side of the exhaust manifold thru a 90* fitting. That pop off valve is in there.

Just so you know there is more to the cooling control besides the thermo itself......
 

5forfighting

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Re: Johnson 70 HP Slow Mode 1998

noted. thanks. I will try the tub later today, weather permitting.
 

gtg805

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Hi 5forfighting,

Just wondering if you ever got to the bottom of this? I have the same engine with the same issue.
 

racerone

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Look for / check for a sticky NEUTRAL SHIFT SWITCH.-----It is a part found on the motor linkages.-----If the computer gets a signal that motor is in neutral it simply will have no power ( won't rev up )
 
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