Still need help with my '76 Mercury, not running well, still bogging, what do I

Massey

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Joined
Jun 20, 2002
Messages
7
I wrote a message a couple of days ago and I really appreciate the responses. I checked my spark plugs and found a local place that carried replacements. I changed them, and it did seem to be better. My cousin and I set the timing to the best of our abilities (he's a certified vehicle mechanic) and found that the timing was at 16 BTDC, and it was supposed to be 23 BTDC. We changed it, and out of the water it seemed to be great. We put it in the water saturday and at first it seemed ok. Took a while to start like always, but, once it got going, it was incredibly smooth! We started out slow till out of the 5 mile an hour booies, but, when I hit it, it still didn't respond the way it should. It took almost a full minute to get to full speed, but it sounded smooth and sounded good. But, by the end of the day, it was rough, hard to keep running, and hard to get out of the hole. I checked my prop, it is torn up a little on the edges, a few small chips, and generally worn...but it's a 19 pitch, the stock for this motor. There was a replacement propeller with the engine when I got it, but it's in even worse condition but it's a 21. So, if anybody could please help me out??? I'm dying to get this thing working! Thanks, Major
 

12Footer

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Mar 25, 2001
Messages
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Re: Still need help with my '76 Mercury, not running well, still bogging, what d

Re: Still need help with my '76 Mercury, not running well, still bogging, what d

76 Merc 115HP (went back and found original post)..<br />Do you have a tach? Even if not, does the RPM's sound like a slipping clutch on a car?<br />If so, the hub has spun out in the prop. Iether case, I would take the prop to a prop shop,and have it reconditioned. It will cost less than half of what you would pay to repair the lower unit after using an unballanced prop over an extended period.<br />And you will rule-out prop problems. The 21pitch would load-down the engine,if you are allready having problems getting it up on plane quickly.<br />17Ft boat with a 115 Merc 'tower of power' should haul buggy,and make a rubber band outta that tube, and the guy that's in it.
 

RandyJ

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Jun 13, 2002
Messages
808
Re: Still need help with my '76 Mercury, not running well, still bogging, what d

Re: Still need help with my '76 Mercury, not running well, still bogging, what d

I didn't have the opportunity to catch your earlier post but from the description I'd be sure to go over the most common ailments... fuel line sucking air at o'rings, fuel pump, trash in fuel, etc. I've got a 1978 50 hp that had similar problems. I beat my head against the wall until finally a coil TOTALLY gave up. It had an intermittent coil which worked up until 1/2 throttle. After the total burn out it was easy to find the problem. I could have found it by pulling the plug wires one at a time while running above 1/2 throttle... which is a tricky act but pretty much the way a shade tree mechanic does it.
 

RandyJ

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Jun 13, 2002
Messages
808
Re: Still need help with my '76 Mercury, not running well, still bogging, what d

Re: Still need help with my '76 Mercury, not running well, still bogging, what d

A PS to the above reply. I almost always start a diagnosis or evaluation of a motor by checking the compression. You should have 125 psi on all cylinders. At the very least you should have over 100 psi and all within 10 (definitely not more than 15 psi) differnce between any two cylinders.
 

zaneh

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Apr 24, 2002
Messages
13
Re: Still need help with my '76 Mercury, not running well, still bogging, what d

Re: Still need help with my '76 Mercury, not running well, still bogging, what d

Hello Major,<br /><br />Gotta love those inline mercs.......Sounds like you are running reaaally rich. After checking your compression, check your fuel pump diaphram, even with just a small pinhole, they will cause excess fuel to be drawn into the crankcase causing an over rich condition. If it looks ok, replace it anyway, the fuel pump kit is cheap. Then check/clean your carbs, you may have leaking float needles. Does gas run out of your carbs when you tilt your motor up to the trailer position? Does fuel run out of the carbs when you pump the primer bulb? If so check those float needles. Good luck.<br /><br />Zane
 
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