Mercruiser bogs and dies

sealyons

Seaman
Joined
Jul 20, 2004
Messages
67
1985 Merc MR 200 runs ok in neutral and underway when slow, but once given some throttle it bogs down & dies. It will restart and stay running if feathering the trottle and will ultimjately idle 'normal' again after a short while. I am able to rev high in neutral and it will happen as well. Replaced fuel filter, plug wires and cleaned cap & rotor. Fuel is new this year and has stabilizer in it. Carb is a 4bbl rochester quadrajet. Had fuel issues last year and changed tank. I would appreciate any suggestions!
 

wooly

Cadet
Joined
Jul 12, 2010
Messages
7
Re: Mercruiser bogs and dies

I had a similar problem, cutting out when accelerating, try changing the coil, I changed from a merc to a bosch and everything is now good.
 

sealyons

Seaman
Joined
Jul 20, 2004
Messages
67
Re: Mercruiser bogs and dies

I did replace the coil, and still same symptoms. I plan on hooking up an external fuel tank to see if it is delivery problem between the tank and fuel pump next.
 

Bob_VT

Moderator & Unofficial iBoats Historian
Staff member
Joined
May 19, 2001
Messages
26,048
Re: Mercruiser bogs and dies

Common problem....... it may be time to rebuild the accelerator pump in the carb....... be sure to use a marine grade repair kit.
 

sealyons

Seaman
Joined
Jul 20, 2004
Messages
67
Re: Mercruiser bogs and dies

I also forgot to mention that the tach shows a very high RPM 4k when first started and then back's down to the norma 1500 to 2k i have it warming up at. The engine is not running that fast, tach is just registering high initially. I plan on running from external tank to verify that it is not a leak on the tank/ water separator side of the system. Also going to change the plugs. I had a similar problem years ago that was fixed with a new coil, the new coil I put on this year didn't fix the problem.
 

shopboy

Seaman Apprentice
Joined
Apr 28, 2010
Messages
30
Re: Mercruiser bogs and dies

I had the same probem. Mine was carb related BUT

I've read that if your tach is malfunctioning it can ground out the coil causing running issues.

The tach wire is connected to the negative pole on the coil I believe. You can test this by removing the wire and running
 

6meter

Chief Petty Officer
Joined
May 15, 2010
Messages
525
Re: Mercruiser bogs and dies

Previous tank issues could mean the carb is dirty inside. Time for a rebuild.
 

sealyons

Seaman
Joined
Jul 20, 2004
Messages
67
Re: Mercruiser bogs and dies

Mystery solved....somewhat. Found the fuel filter in the carb almost completely plugged it's amazing it ran at all. Had it out for over an hour yesterday and it ran well though I never opened it up completely, I had it at higher RPM's than I had earlier when I experienced the issues. Plan on getting it out in the next day or so to put it through the paces. Tach is still erratic, shows higher than engine sounds and then comes back down and repeats with no regularity. Also shows about 1k whan the key is off...
 

shopboy

Seaman Apprentice
Joined
Apr 28, 2010
Messages
30
Re: Mercruiser bogs and dies

Maybe try to find another tach to borrow and install and see if the problem still exists..

If so, you'll need to find the problem in your wiring... Check all the connections etc...

I think its normal for some tachs to stay above 0 when turned off, but the fluctuation while running is definitely an issue.
 

BIGALF

Petty Officer 1st Class
Joined
Dec 31, 1969
Messages
242
Re: Mercruiser bogs and dies

I suggest you also check the filter in the fuel take. I had that problem and found that the take filter was also clogged.
 
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