Hard to start, won't idle, white/gray smoke...for a bit

chartscharts

Cadet
Joined
Feb 28, 2018
Messages
9
I have a 1990 GM305 V8 5.0L Alpha 1.

It's been about 6 weeks since I ran it, and that was just a maintenance start, and it had been about 8 weeks prior to that since it had been started. I've gotten life under control to the point where I can be boating again, so been doing some maint.

Fired it up today to run it a bit.

It was hard to start, turned fine, just didn't catch, and when it did, it didn't want to idle (stall), and had way more white/gray smoke coming out of the prop than normal. After running it for 15-20 minutes it worked great, in and out of gear, idled fine, etc....

My diagnosis is "Older engine....Hasn't been run much in the last 5 months."


But I'm hoping to learn and there's probably technical/mechanical reasons for this behavior. Does anyone know what they are?

Thanks in advance for any clues. I've learned a lot from you guys and want to keep learning!

-Charts
 

havoc_squad

Senior Chief Petty Officer
Joined
Mar 5, 2011
Messages
694
If you want to rule out issues, probably a good idea to do a compression test on all cylinders if mentioning white smoke coming out.

White smoke typically results when water/condensation ends up in the cylinders, much like what happens if a head gasket leak occurs near a coolant channel.

If you get a lot of oil blowby coming from the valve covers out the breather

You might want to go to www.boatinfo.no and look at the manual for your engine on the minimum acceptable compression. Keeping in mind compression readings on all cylinders must be within 10% of the highest and lowest reading of all cylinders.

If you get a problematic cylinder(s), you will want to do a leak down test to find out where the problem is before you go any further in spending money or time.
 

Grub54891

Vice Admiral
Joined
Jun 17, 2012
Messages
5,908
I'd like to add, assuming it's carbararated, that being a 1990 It may me getting gunked up a bit. Hard starting after sitting with a bad carb could be an issue. The white smoke could be condensation as stated, but checking out the motor is never a bad idea. I drive older cars, they work well. Any motor or equipment that sits around to much will have issues from sitting.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
White/gray smoke is never good. As already stated, water/condensation getting into the combustion process. Check compressions, and I would also be checking exhaust manifold for cracks or leaking around the elbow gasket.

Chris..........
 

chartscharts

Cadet
Joined
Feb 28, 2018
Messages
9
Yeah, after starting a few more times in the last week and two, there hasn't been nearly as much white smoke, hardly any...so my guess is that after a long sit with no running, some moisture condenses in there. But clears out after I run it. And if I run it regularly, it never builds up.
 
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