Engine Won't Run When Warm

[racerone]

Nope----The bottom of the rectifier is fully in contact with water.----Gasket is there to prevent water from leaking out !!

 

[flyingscott]

Or, since water doesn't go through it, the gasket insulates it from the hotter aluminum.

Two ways to look at it.

It sits IN the water Jacket

 

[Faztbullet]

Most likely a air leak in VST

 

[twoelvis]

Yes, the rectifier is water cooled. The OEM rectifier has nipples. The aftermarket replacement rectifier has fins. I replaced the rectifier, and reused the old gasket, until the new one arrives. The old gasket had no damage. The rectifier has fixed the tachometer problem. But, the new rectifier has not fixed the idling problem.

I ran the motor on the trailer, and I noticed that this problem is occurring all of the time, not just after 30-60 minutes. I guess that I did not notice the problem for the first 30-60 minutes on the river, becasue I was at least 1/4 throttle for the first 30-60 minutes, and did very little idling. So , I am changing the description of the problem to "will not idle reliably at any time". One thing that I noticed is that toggling the choke on and off every few seconds will keep it idling. In my mind, that means that the engine is not getting enough fuel. I am attaching attaching a photo of all 4 plugs. The plugs were pulled after I toggled the choke on and off. So, I am not sure if that will effect the spark plug diagnosis.

 

[saltchuckmatt]

Now it's time to figure out whether it's spark or fuel. Personally, is get rid of those plugs and buy champions but others will disagree. Either way I'd start by doing a spark JUMP test and if tests fine go on to fuel.

 

[twoelvis]

Now it's time to figure out whether it's spark or fuel. Personally, is get rid of those plugs and buy champions but others will disagree. Either way I'd start by doing a spark JUMP test and if tests fine go on to fuel.

Spark checks out good. In my mind, it is not getting enough fuel. Any introduction of additional fuel in to the intake, either by spraying, or by choke, keeps it running. It does not sound like just one cylinder that is bad causing the problem. It seems uniform across all 4 cylinders.

 

[Crosbyman]

fuel tank vent working ?? pick-up tube clean ? hose ok ?

 

[twoelvis]

I just replaced the fuel tank, fuel lines, and primer bulb. I am new to outboards. Are the fuel pumps electric, or powered by vacuum?

 

[saltchuckmatt]

Powered by a pulse from the crankcase.

 

[racerone]

Wires to the fuel pump are for the --" no oil "---warning only.----The fuel pump operates with a PRESSURE pulse and slight low pressure pulse from the crankcase.----Has the water pump impeller been replaced ?----And post the actual values you get from a compression test.-----VRO in service and tested ??----Vapor pump tested / inspected ?-----Gasket on the vapor tank checked for leaks ?

 

[racerone]

edited

 

[cyclops222]

Spark plugs are BOTH black and unburned oil. Check the cylinder head temperatures of all cylinders. It looks like your thermostat is keeping the engine too cold.
I use 1 Heat Range hotter than standard. I use NGK standard duty. No Iridium needed.
New CORRECT sparkplugs first. Runs much better ? Then starts same old problem. Thermostat is not holding correct temperature.

 

[twoelvis]

Wires to the fuel pump are for the --" no oil "---warning only.----The fuel pump operates with a PRESSURE pulse and slight low pressure pulse from the crankcase.----Has the water pump impeller been replaced ?----And post the actual values you get from a compression test.-----VRO in service and tested ??----Vapor pump tested / inspected ?-----Gasket on the vapor tank checked for leaks ?

I did not do a compression test. I was assuming the internal engine was in good shape due to low hours. But, I guess that I should go back to square one and do the compression check. I am assuming that I should do the compression test when the engine is warm? It is tough to get the engine up to running temperature, because it will not idle on its own. The only way that I can keep it running is to either rev it up, spraying gas in to the intake, or toggling the choke on and off. What is the safest way to get it up to temperature running it with the muff on the trailer?

Can you point me in the direction of how to test the VRO and vapor pump?

 

[twoelvis]

Spark plugs are BOTH black and unburned oil. Check the cylinder head temperatures of all cylinders. It looks like your thermostat is keeping the engine too cold.
I use 1 Heat Range hotter than standard. I use NGK standard duty. No Iridium needed.
New CORRECT sparkplugs first. Runs much better ? Then starts same old problem. Thermostat is not holding correct temperature.

It may not have been up to operating temperature when the plugs were pulled. I was toggling the choke on and off, in order to get it to run.

 

[twoelvis]

It may not have been up to operating temperature when the plugs were pulled. I was toggling the choke on and off, in order to get it to run. I have realized that the problem occurs all the time, not just when warm.

 

[racerone]

I never warm up an engine to do a meaningful compression test.------------Sorry , too much typing ( blisters on finger tips ) to explain VRO test.----A factory manual has the procedure.----I picked up a 2001 version of your motor for parts.----Low hrs motor that new owner did not commission properly when motor was installed.----Scored all cylinders.

 

[saltchuckmatt]

Agreed, less worrying and more diagnostics. Just compression as it lays will give you a general idea.

Stop running this motor and determine if this is a lean running issue like I believe you already know.

 

[twoelvis]

I did a cold compression test. All 4 cylinders were 131-136 psi. I could not find a compression spec. But, since all 4 were similar, I think that means compression is good?
I am still trying to find more info on testing the VRO. But, I did find out how to test the fuel pressure. So, I am going to do that now.

 

[saltchuckmatt]

Probably more ways to test the vro, but one way is to run with a portable fuel tank at a measured amount with 50 to 1 in it just to make sure it doesn't burn up the motor and then do a measured amount of two stroke oil going into the vro. You then high idle it and do the calculations to see if you're getting somewhere of 75 to 1 or a 100 to one in the idle range.

 

[twoelvis]

I am noticing that one of the carburetors is spitting out gas in to the air intake box. Is it a bad reed causing that?