Any Ideas?

Thanks for all of the suggestions. I figured since I am getting a tech to diagnose that I would let him check fuel pressure.
The battery idea is interesting. I have read a few threads where bad or low batteries caused issues. Upon checking my logbook I see that the batteries on that side are 7 years old. I will be buying new ones this afternoon and will give it a Hail Mary...at 7 years old I won't feel like I'm wasting money on a possible fix as they must be getting aged out in any case.
A CFM swap would be a last resort for me as it is a PITA and could open up a hornet's nest of other problems.
 
True on the CFM. 7 year old batteries would certainly be suspect. I change mine out every 4 years. I have learned that our motors are very sensitive to voltage fluctuations and a properly functioning electrical system is crucial.
 
Korkie said:
True on the CFM. 7 year old batteries would certainly be suspect. I change mine out every 4 years. I have learned that our motors are very sensitive to voltage fluctuations and a properly functioning electrical system is crucial.
Click to expand...
Does your mechanic travel to Long Island??? Lol
 
Update...Installed new batteries on port side after charging them fully externally. Engine started immediately and ran well for 15 seconds , faltered and died. Restart , ran 5 seconds and died. Trouble restarting in 2 subsequent attempts. Basically would not restart.
Removed flame arrestor , opened throttle 20% , cranked and sprayed ether. Engine started and continued to run at 1250 RPM somewhat roughly without any additional ether. Oil pressure good at 50 PSI. Exhaust is abnormal in my opinion as the water effluent has a white shade to it. Decreased throttle position slowly towards idle and engine quit around 800 RPM. No sheen left on water and closed cooling resevoir is remaining at normal level. No sign of water in oil.
So , it is getting spark , it is getting fuel , but it appears it is not getting enough of one or the other or possibly not getting it at the proper intervals. Even though I replaced all plugs with proper AC Delco's 30 hours ago I am tempted to put 8 more plugs in and see what happens. I think it is unlikely that it will solve my problem. Coils? Ignition wires? I think it is unlikely that enough of those failed at the same time to cause my problem.
And so it goes...
 
Just got off phone with my merc service manager and first thing he said was IAC. Told him you had replaced it, and he asked was it OEM. Told him I did not know. His suggestion was if not, needs to be OEM. Suggested swapping with other engine to see if follows. His next concern was that the 5 volt IAC (DRIVER) control in the computer went bad. Has seen this a dozen or so times a year. Suggested swapping the computers on the engines to see if problem follows. He did say the smart craft was going to go a bit haywire during the swap, but the engines would still start and run. Gauges all backwards, etc. His theory behand all this is it runs well after it is warm. As once the engine is at a certain temp, the computer doesn't use the IAC valve data. If it is the computer that ends up being the issue, he has a contact that he will share with me that he has used many times that you can send it too and he can verify the IAC circuit is bad and most times can repair it.
In reading what you just did, I agree it isn't spark or fuel as the motor does well after it is warmed up. The IAC valve has always been the culprit in this scenario.
 
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IAC replacement was not OEM. I tested the original OEM and it tested good but I replaced it anyway. I will try switching the good engine IAC as it is easy but am not very hopeful.
I am hesitant to switch computers as I have read that you can burn the good one out if there is some sort of wiring fault that caused the port to screw up in the first place.
Putting the suspect port computer on the good engine to see if fault follows may be a safer option.

Very much appreciate you asking your mechanic for ideas and the computer contact if needed.
 
If it's IAC related, cracking the throttle at the helm will essentially created your own vacuum leak. If it stays running, I'd look down that path. However, if it ran on ether, it sounds fuel related to me.
 
To be clear , when the throttle is cracked and a start is attempted , it will not start.

When the throttle is cracked and ether is sprayed into the throttle body , it will start and continue to run on its own fuel supply without any additional ether. It runs quite rough though as if only running on 6 or seven cylinders.

The only vacuum line I'm aware of is the one that runs from the intake manifold to the fuel regulator and it is intact and not blocked or kinked.

Today I am going to double check that I didn't cross any of the spark plug leads and switch the IAC from the good engine.
 
sejensen737 said:
To be clear , when the throttle is cracked and a start is attempted , it will not start.

When the throttle is cracked and ether is sprayed into the throttle body , it will start and continue to run on its own fuel supply without any additional ether. It runs quite rough though as if only running on 6 or seven cylinders.

The only vacuum line I'm aware of is the one that runs from the intake manifold to the fuel regulator and it is intact and not blocked or kinked.

Today I am going to double check that I didn't cross any of the spark plug leads and switch the IAC from the good engine.
Click to expand...
Plug wires are fine, the problem goes away when the motor warms up. So it can’t be plug wires or the problem would persist constantly
 
I hear you about plug wires but this is the difference...I let the engine run roughly for 4-5 minutes (even though it hurt) , and it never smoothed out as in the past. The difference between now and then is all my monkeying around with the plug wires when I pulled the plugs for borescope. I'd be surprised if I screwed that up but will double check. Temperature gauge was just starting to rise off the stop when I shut it down.
 
Not a good summer so far. Car died a few days ago so have been dealing with that.

Double checked spark plug wires and they were all connected properly. Switched OEM IAC from starboard to port. No change. Exact same symptoms. First start runs 15 secs dies. Second start runs 5 secs and dies.

Can anyone educate me on the exhaust and muffler? Are there any flapper valves (other than the external one at the stern) internally that could possibly be hanging up?

Still at a loss for solution. My appointment for a diagnosis should be about another week...meanwhile another beautiful day on Lake Huron
 
Have you checked the IAC passageway in the throttlebody? Have you checked IAC movement with it removed from the TB
 
"Have you checked the IAC passageway in the throttlebody? Have you checked IAC movement with it removed from the TB"

Yes to both

I've suspected possible fuel injector blockage or failure from the start of this saga and am leaning that way again after everything else has not worked. The fuel filters in the CFM were not really bad and the filter in the regulator was pristine so injector blockage is less likely than failure of a couple of injectors IMO.
 
Since it fires when you use ether it sound definitely like fuel related. It may be injectors, it may be fuel pump. Pressure test for sure. Do you have Smartcraft and if so, does it monitor fuel pressure? I would doubt its the ECM. However, the other thing I am suspicious of is you said it runs better when warm. This may indicate ECM issue as during open loop (Cold) operations signals are coming preset from within the ECM. But when warm, or closed loop, sensor signals are used and Its running OK meaning probably wasnt the IAC or TPS to begin with. Keep us posted on Fuel pressure. I am curious of that.
 
Update

Got tired of waiting for my turn for a mechanic. Was told 4 weeks ago it would be 2 weeks. Anyway...

Bought fuel pressure gauge. Put it on bad engine and checked fuel pressure via recommended Mercruiser method. Good pressure , 42psi but bled down immediately to 10 psi. Hmmm...not right I'm thinking so I check fuel pressure on good engine and 42psi and holds pressure.

So , could be a number of things but does anyone out there have experience with this particular symptom and how was it rectified?
 
Update

Put everything back together and it started but ran like crap. Idling initially at 580 rpm and would stall if throttle applied but it did keep running which is an improvement (sort of)
Once warmed up a little , will accept throttle and ran it up to 2000 rpm but running roughly. I ordered a new injector to replace the one with the missing cap but I thought I would try an engine run with the defective injector. I find it hard to believe the engine would run so rough because of that injector.
The faulty injector was cylinder #2. You can see the o-ring stuck in the port. It was pretty scabby in that area. Cleaned it all up. Bottom of fuel rail was scabby too but no perforation. Cleaned it up and painted.
So it appears I'm not that much further ahead...
By the way , I've been puzzled by the corrosion on the fuel rail and as previously mentioned , on the far starboard exhaust manifold. I have not been able to find any source of water spray in that area but I did notice that my CFM's have threaded nipples for the water coolant. I'm thinking that the CFM's may have been replaced by the previous owner due to the well known lack of integrity of the original design with the plastic fittings.
 

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Update

Today I tested the fuel pressure while engine was running. Not easy to do when engine does not want to run.
Anyway , got it started. Fuel pressure 42psi when pump energised and dropped to 35 psi while running. I think this is normal because I performed the same test on the good starboard engine and the results were the same.
I was hoping the pressure would drop off and confirm a problem with the high pressure fuel pump. No such luck.
 
Ok, so I am exhausted of ideas now other than injector problems. Hopefully others can weigh in on the 35 psi during higher RPM. Seems low to me but if starboard engine runs fine at that PSI, its likely normal. In light of no other codes being thrown and stored in memory, I am thinking injectors. It wouldnt surprise me if, in your area, ethanol fuels are sold at marina's that the injectors/seals are toast. Hopefully others have opinions and can help. Again, keep us posted.
 
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