Proper way to start engine

[Presentation]

.........My 4.3's do just the opposite. They fire off great cold, but crank over forever when hot. So much so that I have to push the throttle past 1/4 and they start right up. When I bought the boat the mechanic went out numerous times, changed the iac's, the filters and evrey thing else. His latest "fix" was to raise the idle a little. All this does is make it pain to dock. I would like to get this fixed someday! If you just go ahead and give 1/4 throttle at the beginning they fire up. If not, you will have to and then you will smell gas when they start like they were flooded. Funny thing is they both do it and they do it after they have been running a while:huh:

New plugs, cap, wires, rotors iac's, iac filters, yada yada!!:smt101

I recommend you start a new thread and see what we can come up with. Based on your description it sounds like a fuel cooler issue. My knowledge on the 4.3’s is low. Dennis or Tech Smith may be able to help you more then I can. What can happen is after your engine is hot and you shut it off, simple convection can cause the hot water to flow backwards thru the hose that runs to the cooler.

This hot water brings the fuel to a boil. The fuel expands and causes a vapor lock, basically a gas pocket. As long as you keep running, fresh cool fuel prevents the issue. A hot engine + lack of fuel movement causes this issue. If you let the engine cool , say over night, the problem goes away because the heat goes away. Also, salt buildup could be causing a partial blockage in this fuel cooler.

If you let the boat idle for a long time, say 10 minutes, allowing your engine to cool before you shut it down then you don’t have a issue, this would be confirmation that your issue is with the fuel cooler. Keep your bilge exhaust fan running during this 10 minute cool down period plus an additional 10 minutes afterwards.

We can discuss additional diagnostics and recommendations but it should be in your own thread.

 

[Gunn]

Great info Presentation, thanks. I think I'm pretty accurate in the 3 seconds for my engines (as I listen to them cranking over in my head). I had always wondered if that was the norm or not. It's not a long time, but in comparision to fuel injected cars I've owned, they usually start in about 1 second, no matter hot or cold.

Oh, and thanks for the plug removal tips, not really looking forward to it!

Still going to replace all of those items anyway, just to start building a history for this boat, and begin to trust it a little more when we're far away from home...

 

[gregkjones]

....... Once fired up, the engines seem to surge a few times before settling to a smooth idle.

Anyone ever heard of this??

Yes, mine do that. After start a couple surges and then its set. There are boats starting around mine all the time since I am located near a dock that has boats for sale, every brand out there. Many of them in fact most of them, have that surge for a couple seconds after start. I think it is just the way the MAPs and other air sensors work; takes a second for everything to settle in after start.

 

[pineknollj]

I am hoping to get some assistance with understanding timing and how to set it on my 2005 320 5.7L Sundancer. I am looking at the knock sensor and it might need cleaning as we are getting some wild shifts in RPMs above 3700. I can hear it knocking, but it is not auto adjusting as I read it is supposed to do. Mechanic slightly adjusted timing and it ran WAY better, up to 4700 WOT, and now back to banging again.

Looks like you may need to setup with the computer equipment to the ECM as there is no typical marking on the harmonic balancer to gauge timing with a regular timing light?? He told me the cap and rotor looked fine, but will investigate myself in the morning.

Any feedback or assistance is greatly appreciated. sensor assembly 878187 is part number from
https://public-mercurymarine.sysonl...=GuestNA_KEY=NA_KEY_VALUElangIF=englangDB=eng

Thank you!
John Clarke