89 Johnson 70 hp over heating issues (slow mode)

[fishfeatures]

Re: 89 Johnson 70 hp over heating issues (slow mode)

ooooh me thinks we have a double identity going on here, isn't that right Scsdiver or should i say TURBO4DOOR !!!!:faint2:

 

[scsdiver]

Re: 89 Johnson 70 hp over heating issues (slow mode)

i posted yesterday on my counter parts post we did not realise the other had made a post. sorry there was two initial threads going for us but we there is two of us whom own the same engine.

The vinegar is pretty close to neat! we have a 32 gallon tub. there is 16-17 gallons of vinegar and 3-4 gallons of water. it removed a considerable amount of trash and we know it is not a quick remedy but i believe there is enough well documented post on here about the very positive effects straight vinegar has on a very corroded motor. Nitric acid seems a bit harsh to be running through some plastic/rubber parts? however as noted in my post this morning the low 150's is the hottest temp we saw last night while running it. we will post tongiht on our progress.

 

[turbo4door]

Re: 89 Johnson 70 hp over heating issues (slow mode)

i posted yesterday on my counter parts post we did not realise the other had made a post. sorry there was two initial threads going for us but we there is two of us whom own the same engine.

The vinegar is pretty close to neat! we have a 32 gallon tub. there is 16-17 gallons of vinegar and 3-4 gallons of water. it removed a considerable amount of trash and we know it is not a quick remedy but i believe there is enough well documented post on here about the very positive effects straight vinegar has on a very corroded motor. Nitric acid seems a bit harsh to be running through some plastic/rubber parts? however as noted in my post this morning the low 150's is the hottest temp we saw last night while running it. we will post tongiht on our progress.

Made a little progress tonight. We now have an alarm. Took the boat out tonight and ran it again. Entered slow mode again with a solid alarm tone. Checked temps on the block near the plugs and found temps running no higher than low 120s and block felt almost cool to the touch. As a test we unplugged temp sensor bullet connector and ran a short distance. Boat ran really well. Temps around 145 max. Ran a bit further and saw the highest temps at low 160s and high 150s. We were able to power right out of slow mode after unplugging temp sensor without shutting motor off.

Temp sensor is brand new, but is not the higher value sensor with the blue trace on the tan write
Motor ran very smooth art the start of our outing, little rough as we pulled up to the ramp to take it out, but think we may still have some slight carb issues to clear up.

I guess I'm not really sure where this leaves us. I don't know that it's really over heating.bad power pack? Wrong temp sensor? I know the v r o will sound a constant alarm tone too, right? It's has been removed and we premix

And yes, there was two posts, but we are two people! We co-own the boat and would like to use this as our running post, not the other.

Again, Thanks for all of the help so far (this place is awesome!), hopefully with your support we can get it running properly.

 

[WernerF]

Re: 89 Johnson 70 hp over heating issues (slow mode)

Now the alarm makes troubleshooting much easier. If your temperature readings are right and the block was really "almost cool to the touch" when the alarm occured, two possiblities are left.
1. The temp sensor sits in a hot spot due to a clogged water passage.
2. Your new temp sensor is bad and triggers on a too low temperature.
You need to test the temp sensor in a pot on an oven with a multimeter and an accurate thermometer (an infrared thermometer isn't accurate on water). Warm up slowly and measure the temperature the sensor closes.

You might have to pull the head to check the water passages.

What about the thermostat? Did you replace the vernatherm element only or the complete plastic thermostat assy? The plastic might have deformed due to a previous overheat.

The VRO would make an intermittent tone. But due to a diode in the tan wire located in the engine harness the VRO would cause an alarm, but NOT trigger SLOW mode.

 

[scsdiver]

Re: 89 Johnson 70 hp over heating issues (slow mode)

i ordered a head gastket the other day but we will deff pull the temp sensor out tonight and try that. i can tell you when it went into slow mode the first time last night the block was somewhere between cold and luke warm. i believe your first option is going to be the most likely based on the amount of scale we found in the water cover. in regards to the thermostat we replaced the whole assembly. i believe the thermostat is working as it should as we could see the water coming out of the top exhaust ports while running it in the tub progressivly more as the motor got warmer.

Thanks again guys we Really appreciate your help!!

 

[Faztbullet]

Re: 89 Johnson 70 hp over heating issues (slow mode)

Ohm the sensor when it triggers SLOW, if it is reading to ground it tripped the Slow feature, if not your pack may be bad, check org wire from pack to sensor for chaffing.

 

[scsdiver]

Re: 89 Johnson 70 hp over heating issues (slow mode)

thank you all so much for all the assistance. we believe we have finally conquered our issue. after the night before last we deffinetly figured out the power pack was good and the temp sensor was closing. last night my counterpart pulled the temp sensor we just replaced and the new one and tested both as well as the thermostat and they all worked. so we removed the head to find a ton of scale build up and some how a piece of carbon! we honestly believe the real problem and the reason it was so intermittent is the piece was floating around at the bottom of the water jacket to the cylinders. we think it was bouncing around and once water started flowing it was large enough to restrict flow to half of the cylinder and deff hampering proper water flow. we also had two of the holes that go from the cylinder area to the exhaust area were completely plugged up and the others were definelty comprimised in one way or another. anyways we cleaned out all of the scale it looks like a new block again! we went and ran it and it performed perfectly we did check head temps after our first run and temps were down around low 140's after running steady at 3300rpm for a good 20-30 min the temps only came up to 145 at the hottest spot i found the bottom of the head was around 140-142. thank you guys again for all the help and hope this helps some one else down the road!

 

[WernerF]

Re: 89 Johnson 70 hp over heating issues (slow mode)

I'm glad to read that you've fixed it!

 

[turbo4door]

Re: 89 Johnson 70 hp over heating issues (slow mode)

As my friend said, last night was a great night! Motor ran amazing. Very smooth, solid, and it was a great feeling to finally get it running right. Also, as mentioned, thank you guys for the support. Places like iBoats are amazing tools to the average person, and iboats has been one of the best I've seen.

 

[fishfeatures]

Re: 89 Johnson 70 hp over heating issues (slow mode)

well guys I never guessed that were two of you... glad to hear you may have the issue sorted..

 

[phillnjack2]

Re: 89 Johnson 70 hp over heating issues (slow mode)

I have to agree on above statement about iboats being a great forum.

so many people willing to help and so many having had the same type of problems with help and advice.

also some realy good knowledgable marine engineers who give us all help and tell us how to fix things simply
and in plain terms.

great forum


and glad your engine is fixed and running well turbo4door/scsdiver


phill