1987 Mercruiser 165 i4 cranks but won't start

[Someguyincali]

Had the boat in the water last week for a couple hours. No issues. Took it to the water today and it would not start. Intermittently tried to fire and actually got it to start for a second before dying.
I have spark.
I have fuel pressure both from the accelerator pumps and the fuel pump.
Fuel is fresh.
There is no kill switch that I am aware of.
I have read through other posts with the same problem but none of the solutions to those posts applies here. Don't think it's timing since it ran just fine a week ago.

 

[Scott Danforth]

check out links 18-20 https://forums.iboats.com/forum/eng...ion-for-diyers-an-work-safe-search-version-of

 

[Someguyincali]

check out links 18-20 https://forums.iboats.com/forum/eng...ion-for-diyers-an-work-safe-search-version-of

Yeah I followed that and I'm still at square 1. 1 have good strong spark at every cylinder. Plugs look good. Fuel is pumping strong. Engine won't start even with starter fluid. Confirmed firing order with wiring order. Tested coil. Points are clean and shiny.
No firing at all.

 

[Scott Danforth]

And you verified timing?

 

[Someguyincali]

Timing was perfect last week. Not sure why it would change...

 

[Someguyincali]

[No message]

 

[Maclin]

Take the distributor cap off and crank it, make sure the distributor is moving in synch with the rest of the engine.

 

[Someguyincali]

Take the distributor cap off and crank it, make sure the distributor is moving in synch with the rest of the engine.

Yes the rotor is moving. And I confirmed the timing.

 

[Someguyincali]

Well, I went to replace all the plugs and the last one closest to the stern was rusted out. The nut on the plug disintegrated a d left me with only ceramic. I broke off the ceramic and pulled out the plugs core. I then used a square extractor to remove the plug casing. Once I put the plugs in I used a screw driver to hold the butterfly valve slightly open in the carburetor. Turned the key and sprayed starter fluid at it. Got a cloud of white smoke then smooth idle.

 

[achris]

Starting fluid is a quick way to damaging an engine. Best avoided...

 

[stonyloam]

Looks like you have a bad head gasket. Do a compression check. Common for #4 to blow.

 

[Someguyincali]

Looks like you have a bad head gasket. Do a compression check. Common for #4 to blow.

I did a compression check. Everything is good. #4 gets a lot more water due to it being directly below the transom. Any rain water or swim water will drop right onto plug #4. It rusted the crap out of the plug. I'm going to pack hi temp grease around the new plug to help keep water off of it.