Evinrude 70hp won't run at low speed in forward or reverse

This is a 1999 Evinrude 70hp - have to have the warm up lever up to start even if the engine has only been off for a couple of minutes. We did have a faulty thermostat that the mechanic took out and said wasn't needed. So currently no thermostat in it and this issue still exists. also, we have cleaned the carbs, replaced the fuel pump and installed a new fuel line. Engine runs great at idle but as soon as I put it in gear, either forward or reverse, it sputters and wants to stall out. Runs good at higher speeds. Ideas anyone? Is this related to there being no thermostat or is there something else I should be looking at here?

Re: Evinrude 70hp won't run at low speed in forward or reverse

How do the spark plugs look? If they're fouled or burned, I'd suggest some new plugs first. The motor is fairly new so I'm assuming that the compression is ok but, if you can test it, I would. The thermostat needs to be in there. It's not directly causing the issue you describe but your motor needs to be at 140 degrees (or so) to operate correctly. No thermostat will make the motor run cooler but that will foul the plugs and create the problem you described.

Re: Evinrude 70hp won't run at low speed in forward or reverse

What kind of compression should I see? Been told between 110 - 120. I put new plugs in less than 8 weeks ago but they are not a consistent color now. Is that because of the bad thermostat that was in it? Can you tell me anything about coils? Trying to cover all the bases and get this motor in good operating condition. thanks

Re: Evinrude 70hp won't run at low speed in forward or reverse

First off don't take anymore advice from the so called machanic. You do NEED the thermosat. Pull off plug wires one at at time while running to make sure it's hitting on all cylinders. You may get shocked so have you wife do it.

Re: Evinrude 70hp won't run at low speed in forward or reverse

The compression numbers (whatever they are) ideally should be within 10% of each other. The actual numbers will very from motor to motor but 100+ per cylinder is what I'll assume you'll have. You can test the ignition coils by using an air gap tester set at about 7/16" apart. The ignition spark should be very visible and lively. Since the motor runs at full rpm, I doubt you have an ignition issue. Are you sure you have the right spark plugs and they are gapped at .030? The first thing I'd do is replace that thermostat and the plugs. Use Champion plugs if you can. I don't know what number plug you need but just be sure you find out before you buy them.