Logo
FULL SITE MENU

1992 Merc 3.0L won't start, replaced almost everything

P

pseudomode

New member
I have been sifting through this forum for the past month trying to solve this issue and it has me baffled. I've learn WAY more about this engine than I ever wanted to learn but I haven't learned how to fix this problem. Perhaps someone here can help.

Short story:
I got a call from the marina that my 1992 Sea Ray bowrider 180 was mostly underwater. When I got there, the entire engine and back half of the boat was underwater. The only thing holding it up was the dock lines. After 3 hours and help of the amazing marine division of the local police department, we were able to raise and pump the boat long enough to tow it to ramp and onto my trailer.

When I got the boat home, I did all the things you do to get water out of the engine and all the other systems (no need to go through it all). I started the engine and it ran great. Relieved, I went on vacation. Returned and it wouldn't start. It turns over but no fire.

Replaced:
  • carburetor
  • fuel pump/fuel filter
  • spark plugs
  • plug wires
  • distributor cap/rotor
  • ignition coil
  • ignition module
  • starter
  • oil pressure sensor
  • tilt/trim solenoid
  • all fuses
  • battery
Tested:
  • Plugs are getting spark (timing light test)
  • No water in the gas tank (drained/replaced)
  • Starter cranks the engine, no fire
  • fuel it reaching the carb.
  • Passes compression test (125lbs for each cylinder)
  • checked voltage and continuity on all the ignition wires and harnesses
  • possibly more I'm not thinking of
*attaching some pics of the recovery and the engine as it is today

Please let me know what I'm missing here. I've reached my limit of self-sufficiency and need some professional advise. I'm determined to fix this darn thing before winter!
 

Attachments

  • IMG-6641a.jpg
    IMG-6641a.jpg
    375.4 KB · Views: 7
  • boat2.jpg
    boat2.jpg
    209.8 KB · Views: 7
Follow up:
I got it running but just barely.

I removed the new spark plugs and they had a thin film of carbon on them. I sprayed them with cleaner, wiped them off and put them back in. It started up at that point but ran with a cough and a studder for about 2 or 3 minutes then died and wouldn't start back again. I removed the plugs and again had black carbon them.

As I understand it, this indicates O2-rich fuel if I'm not mistaken. What would cause that?
 
You're running too rich. Not enough air, or too much gas. Take the air filter off. Once you get it running, you need to do whatever you can to keep it running. Running it will dry everything internally by building heat. I have no idea what carb you have, but if it continues to carbon fould the plugs, you might try leaning out the carb about 1/4 turn in if it has idle mixture adjustment screws.
Did you figure out how/why it took on water? Looks like you didn't have the bow facing out into the main channel. That's never a good thing. Bow out in order to avoid wake from passing boats.
 
Ah, ok! That might be the issue. It does have an adjustment screw for that. I didn’t try that since it was set to roughly the same as the one I replaced but with all the other new parts it may need adjusting. I’ll will try today and report the result.

I haven’t even gotten to the leak issue yet. I wanted to make sure it ran and was worth saving first. I suspect it’s either one of the bellows or transom seal. That’s the next problem to tackle. It was docked with bow pointing out to the channel. It’s Lake Washington so it’s a pretty big lake and can get choppy on a busy day. I suspect the bellows failed because I was pulling my kids and their friends on a tube all day before with a lot of sharp turning back and forth. It’s not something we have done a lot of and it may have caused a crack to develop.
Thanks for the reply!
 
A leak in the large bellows for the shaft will cause water to get into the bilge because the transom plate has a hole next to the trim sender/switch wires that acts as an indicator (I can't think of another reason for it to be there, aside from possibly relieving some pressure due to temperature changes since that area is sealed). If the bellows has a leak, your bilge pump didn't work and it was heavier aft, this is why it sank.

The carb was replaced, but did you adjust the fuel/air mix screw properly? Turn it in fully, then back it out by 1-1/2 to 2-1/2 turns (going by memory, so use a manual, to be sure). Since my boat was treated very badly, I assumed a lot of the settings were wrong, so I started from scratch, using the manual for reference. When I ran it on the trailer, it started easily and idle was right on 650 RPM and when I finally launched it, it ran beautifully- couldn't have asked for it to run better.
 
I’m ashamed to admit, I did not follow any “manuals”. I just eyeballed the settings to match the carb I removed. Clearly, I have little experience working on engines. This forum paired with YouTube has gotten me this far. Knowing all the steps involved (and there are many for everything) is the hard part. Being a good mechanic is such long and difficult education. Doctors have it easy.
Thanks a ton! Trying this today.

The leak will be the next headache…
 
pseudomode said:
I’m ashamed to admit, I did not follow any “manuals”. I just eyeballed the settings to match the carb I removed. Clearly, I have little experience working on engines. This forum paired with YouTube has gotten me this far. Knowing all the steps involved (and there are many for everything) is the hard part. Being a good mechanic is such long and difficult education. Doctors have it easy.
Thanks a ton! Trying this today.

The leak will be the next headache…
Click to expand...
If you see a carb that was set by someone else, it's not always safe to assume that it's correct and since it's not hard to count the screw rotations, it's easy enough to put it back where it was if whatever you do doesn't work.

If the large bellows is leaking, water will pass through the hole I mentioned. I was wrong- it's not directly adjacent to the trim wires, it's next to the fitting for the water hose coming from the out drive. Find the hose and look for water coming in.

Don't forget that hull fittings can become loose, including the plug. If you have any raw water fittings, make sure they and the attached hose(s) seal properly.
 
Back
Top