Compression Testing '86 Johnson 90, cold or warm?

[Danthehitman]

Hi everyone, quick question, should I check compression with engine cold or after warmed up? I previously did this cold, all readings at 90 with one at 86.

I have had the boat only a short time and it runs very well once started. On my 4th outing, last weekend, I had issues with cold starts (anchored for 40 had minutes) and had to rely on starter fluid to start. I want to dig into this and figure out if I've got a healthy engine foundation or if this was a result of low compression.

Thanks everyone!

 

[racerone]

Those compression numbers are low.----Could be your tester.----And what is your starting procedure ?-----Are you pushing the key in while cranking it over ?

 

[Danthehitman]

Those compression numbers are low.----Could be your tester.----And what is your starting procedure ?-----Are you pushing the key in while cranking it over ?

My procedure: Motor Cold, Plugs Out, Crank-over about 4-5 rotation.

I did not push the key in or open throttle-lever.

How did I do? As mentioned, the motor runs like a champ but this last outing REALLY let me down for cold starts.

 

[racerone]

To start that motor cold you have to give it some throttle.----You have to push the key in while cranking it over !

 

[Danthehitman]

To start that motor cold you have to give it some throttle.----You have to push the key in while cranking it over !

I always raise the throttle lever all the way up, press the key inward while cranking. This last weekend it gave no indication of starting. I did notice the primer was difficult to get pressurized. I recently read a post where someone said you have to raise it with "arrow pointing up". I've never noticed an arrow, have you heard of this?

What did you think about my compression test procedure? Was I supposed to warm up the engine first?

Thanks for all your help!

Dan

 

[racerone]

I have always done compression test on cold motors !!!----If bulb does not go hard you have a leak somewhere.----Or a bad bulb ( manual fuel pump )

 

[Danthehitman]

The bulb is odd. Sometimes it pressurises quickly, other times it takes 50-some squeezes. I wonder if the full tank effects this, or maybe the bouncing from the 1 hour tow effects this? I tell you, there's a LOT to learn with this boating stuff!

 

[racerone]

Something is wrong with your bulb.----Or fuel tank internal pick up tube.------Or leaks at the carburetors .---Or internal leaks in the fuel pump.-----Test with a borrowed tank and hose.----Should be easy to figure out.

 

[Danthehitman]

Thanks for the advice, I'll do some diagnostic work this weekend.

 

[TuffTurkey]

The bulb is odd. Sometimes it pressurises quickly, other times it takes 50-some squeezes. I wonder if the full tank effects this, or maybe the bouncing from the 1 hour tow effects this? I tell you, there's a LOT to learn with this boating stuff!

This happens to me too. Man I have a lot to learn.

 

[racerone]

If there is an internal leak in your tank it may not come into the picture until fuel level is below that leak !!-----Your primer bulb ( manual fuel pump ) issue should be easy to figure out

 

[tomhath]

I did notice the primer was difficult to get pressurized. I recently read a post where someone said you have to raise it with "arrow pointing up". I've never noticed an arrow, have you heard of this?

Dan

Most primer bulbs I've seen have an arrow indicating fuel flow direction embossed on them. It's there to be sure the bulb is installed on the fuel line in the correct direction so the check valves work.