NS70A2 runs fine on hose, no power at lake

[shellbackII]

This started late last season, I replaced the plugs took it out once to check before winter and it seemed to be solved. Ran stabilizer thru it and put outside for winter. Brought it out this season, fresh tank of gas and some Seafoam engine treatment, bring it out to the lake... and back to the way it was last fall before changing the plugs. Boat can barely can get away from the dock and has to come back, but seems to run fine at home on the hose. Thought it was gas flow ( filter was somewhat plugged) so replaced filter and fuel pump. No change. Revs up great at home, you think you have it licked. There is a very slight sense that something is kicking in and out electronically, but pretty much seems to be running up to par.... BUT ON THE LAKE..it will start up right away, run smooth, and idle...just don't ask any power from it, put it in gear...it kills or at best can idle. Try to accelerate..it kills. Could it be the 250.00 dollar CD ignition unit?

 

[TOHATSU GURU]

Re: NS70A2 runs fine on hose, no power at lake

The symptom is so broad it could be anything. While the engine is running, pull off one spark plug lead and see if there is any change.

 

[shellbackII]

Re: NS70A2 runs fine on hose, no power at lake

What about that CD ignition unit? What symptoms does one have when that is failing?

 

[shellbackII]

Re: NS70A2 runs fine on hose, no power at lake

Thank you! Unplugged one of the two spark plug wires and no change in performance. Unplug the other one and it won't start at all. I guess it's the CD ignition unit.

 

[pvanv]

Re: NS70A2 runs fine on hose, no power at lake

Thank you! Unplugged one of the two spark plug wires and no change in performance. Unplug the other one and it won't start at all. I guess it's the CD ignition unit.

Your diagnostic technique is good, but your conclusion is flawed. Don't jump to conclusions without further testing. You found a cylinder that is dead. That could be as simple as a bad/defective spark plug. Do you religiously run the carbs dry at the end of the day? If not, you may also have a carb issue.

 

[shellbackII]

Re: NS70A2 runs fine on hose, no power at lake

Thank you very much, yes, you are correct, I jumped to a bad conclusion. I spilled a little mixed gas down into the dead cylinder plug hole and that cylinder ran several rev's! So likely not the ignition module. It must not be getting gas?... Squeezed fuel line bulb and gas flows easily out tube that attaches to carb. There's gas in the carb's float. Took off carb, sure looks clean, and blew it out with compressor, put it back on, still, totally dead cylinder.. yet runs when gas is place directly into plug hole..not getting gas? The one that runs is the lower one of the two....any ideas? It ran last season...now the upper cylinder is like ...switched off, dead, Replace carburetor?

 

[pvanv]

Re: NS70A2 runs fine on hose, no power at lake

The upper carb likely needs to be cleaned. That involves removal, a complete disassembly, a 4-hour soak in carb dip, and then a careful reassembly, verifying adjustments as it is reassembled. We would probably do both carbs. We would also do a compression test. Do you religiously run the carbs dry at the end of the day? If not, this problem will come back again.

 

[Outdooradventureman]

Re: NS70A2 runs fine on hose, no power at lake

I had the exact same problem. The final fix for me was to clean the carbs. Someone told me it was the top carb so I pulled it off and it looked clean. I took it back to the lake and still same problem. I went back and pulled the bottom carb and HOLY CRAP it was gunked up like crazy. I soaked it and cleaned out the jets and bowl. Put everything back together and it now runs awesome. I just need to find the factory carb settings somewhere where I can set it back to where it needs to be. The best way I found to test it after you are done is to take a plastic 50 gallon drum and put your foot in it. Fill it up with water and leave the water running in it while you are testing it. This way you can test the motor under load whithout haveing to take it to the lake. If it runs correctly you will sling the water out of the barrel so you can runt it long. Good luck.

 

[weareallnuts]

Re: NS70A2 runs fine on hose, no power at lake

Paul,

My dad used to run the carbs dry on our old '59 evinrude 30. When I got my Grumman with 70A2 Tohatsu, I told my certified Tohatsu mechanic that I planned to do that and he told me not to, that doing so made the engine run without cylinder lubrication a bit before it quit. SO, for the last 6 years, I've not done it. Have had no carb problems... but thought I'd ask, a second opinion is always good and you seemed pretty firm about it to Shellback. Thanks!

 

[pvanv]

Re: NS70A2 runs fine on hose, no power at lake

The fuel mix is just that... a mix. It has oil in it. So as the motor runs out of mix, there is still oil in that mix, just a thinner film. So no lack of lube. Any time you leave fuel in the carbs, especially North American cheap-*** gas, you run the risk of varnishing. If storing for a few months, it's not bad to fog, as you will have a thicker film of oil on everything to help reduce corrosion.