Just got 93 20HP merc and it bogs 1/2 throttle

Jamar

Petty Officer 3rd Class
Joined
Sep 4, 2002
Messages
88
Just got the motor and dont have a manual yet, starting to resarch problem and hope to narrow it down/fix it myself. <br />Here's the deal......upon purchase motor cranked 1st pull and ran great idlng in 35 gallon can. Owner said it had run great in october and had been sitting since. <br />1st test on water and would not open up...cranked easily...between 1/2 and 3/4 throttle it bogs every time. Cranks back up fine when primed. <br />Motor doesnt have a "choke"......but a knob that says "pull to prime". On the cowl above the knob it says turn clockwise and pull out to start, push in and turn to adjust idle. No matter how i have adjusted and fiddled with it it boggs out. Wont start or run without primer all the way out.<br />Seems to be getting plenty of gas. Has new gas, mixed 50.1, bulb was tight, vent open........<br />Smelled rich like too much gas. Used way to much gas and smelled "flooded" and would limp along but bogg down if you tried to open it up. Would appreciate help narrowing this down to isolate the problem. Far from an experienced mechanic, especially with outboards, but a pretty good shadetree if someone could walk me thru what to check in what order. Any help greatly appreciated. If need be will take it to the shop but hope this is something minor and would love to tackle it myself.<br />Not sure if it matters but it has stock merc 10-3/8 x 13 2blade prob and is mounted on bare bones 14' long 4' wide flat bottom jon. Should rip up the river if you ask me. Old 9.8 would anyway.
 

Reel Appeal

Chief Petty Officer
Joined
Aug 19, 2002
Messages
566
Re: Just got 93 20HP merc and it bogs 1/2 throttle

Jamar,<br /> If the motor was sitting awhile and not properly stored,I would suspect carburator problem.It may be gunked up with gelled(old)gas,or debris.Remove the carb. from the motor,dis-assemble/clean out and rebuild if necessary.A thorough cleanout may be enough.Check float and needle/seat for proper movement,etc....Don't teardown the carb. until manual is in hand.Replace worn parts. :)
 

Jamar

Petty Officer 3rd Class
Joined
Sep 4, 2002
Messages
88
Re: Just got 93 20HP merc and it bogs 1/2 throttle

My first guess was a carb rebuild was in order.<br />Just that being too rich and that dang "primer" was throwing me off. Not sure if i should try to rebuild the carbs myself. <br />Anybody got an opinion on whether the 35.00 factory manuals are better than the 25.00 Clymer for this model. Seems all 90-93 are covered in the same manual and not model specific.
 

Jamar

Petty Officer 3rd Class
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Sep 4, 2002
Messages
88
Re: Just got 93 20HP merc and it bogs 1/2 throttle

^^update^^<br /> Yesterday whent i first posted i had just gotten in off the water, was cold, it was almost dark and dinnertime.......so i didnt inspect the situation. <br />Having checked under the cowl today i found the following:<br /> Fuel filter was spotless, nice clean gas.....no specs, dirt, dust, debris or even dried residue in the bottom of the cup. Plugs looked ok, could use replacements but looked reasonable. Anybody want to recommend the best plug for this motor?<br /> More importantly i found one of two small lines off. The end had cracked and loosened enough to come off. The lines are located directly beneath the carb, connected to brass nipples that come out of the plate on the front of the motor that the carb bolts too. Each one runs to a different cylinder, the one in question ran to the top. They appeared to be vacuum lines, but the nipple had fresh mix gas dripping from where the line should have been. This is highly suspect and i know it had to contribute to my problem.....<br />My question is could this been the whole problem. I certainly intend to test drive her before going to the shop first chance i get. Am still wanting on a manual to come in the mail.<br />Can anyone tell me what these lines are and if that could have been the whole problem. Can kick myself for not checking under the hood while underway. Thanks again for everyone who offers advice.......
 

Floridian

Cadet
Joined
Nov 15, 2002
Messages
12
Re: Just got 93 20HP merc and it bogs 1/2 throttle

I've been having the same problem with my 25 HP Merc. I've tried everything except a stator and trigger. I'm taking it to a Marine Dealer on Wednesday, to I'll try to remember to let you know what they find. <br />I'm a retired Aircraft Mechanic of 34 years, not that it means I know anything about boat motors, but I'm mechanically inclined.
 

Floridian

Cadet
Joined
Nov 15, 2002
Messages
12
Re: Just got 93 20HP merc and it bogs 1/2 throttle

I forgot to mention that I checked out a Clymer Maintenance Manual from the library, and scanned the wiring diagrams, etc. and saved it on my computer.
 

Jamar

Petty Officer 3rd Class
Joined
Sep 4, 2002
Messages
88
Re: Just got 93 20HP merc and it bogs 1/2 throttle

Ok i guess i have shown my ignorance by now but think i haved solved my problem at least. Sure would love for one of you seasoned vets to confirm for me though.<br />I checked the exploded parts view on merc parts express. Seems that flat plate i referred to is the cover of the reed valves. Guess that makes this hose that was off the fuel line for the top cylinder. Damn i really feel stupid for not checking under the hood now. (but not as stupid as that guy that thought he just unloaded a bum motor on me)<br />Anyway having no fuel on the top cylinder explains the lack of power......and fuel pumping out into the cowl explains the rich, flooded smell. Does this make sense to anyone but me?<br />Have i pretty well found and corrected my problem from what you have read in my long winded posts? And what damage did i likely do running while starving the top cylinder of fuel/lube. Guess i better check compression tomorrow.
 

dmessy

Chief Petty Officer
Joined
Jul 8, 2001
Messages
505
Re: Just got 93 20HP merc and it bogs 1/2 throttle

Sounds like those are vacumn lines or fuel hoses from the choke to the intake manifold. The main fuel line comes in and is split feeding fuel to 2 or more carbs. From there , the carbs meter the correct amount of fuel to its respective cylinder. Reconnect the hoses and try the motor again, report back. PS- your prop size is fine for your setup
 

Jamar

Petty Officer 3rd Class
Joined
Sep 4, 2002
Messages
88
Re: Just got 93 20HP merc and it bogs 1/2 throttle

Thanks Dmessy, will let you know what happens after test ride. <br />It seems I only have one carb and fuel lines to it are all intact. The line that was disconnected came off the reed cover plate and run up to the back (top) of each cylinder. Not sure if this is some sort of DFI motor or what but whatever the line is it had to be a major part of the problem. Just not sure what i did to the life of the top cylinder starving for fuel/lube while limping along.
 

Jamar

Petty Officer 3rd Class
Joined
Sep 4, 2002
Messages
88
Re: Just got 93 20HP merc and it bogs 1/2 throttle

Whew.....rather be lucky than good any day. Compression test yielded right at 100psi on both cylinders. I know i took years of the life of those rings though. Hope I have cured my problem.<br />Still wainting on opportunity to test her in the water to know for sure.
 

dmessy

Chief Petty Officer
Joined
Jul 8, 2001
Messages
505
Re: Just got 93 20HP merc and it bogs 1/2 throttle

With the lines off , you were sucking air instead of unspent crank gases so I think you were running lean. Might have cause some unwanted wear but those comp. #s sound good. What did the plugs look like? Nice and dark brown hopefully. Whiteish color could indicate a too lean situation but hopefully you have remedied that. Let us know how she runs...
 

bret walters

Seaman
Joined
Mar 2, 2003
Messages
73
Re: Just got 93 20HP merc and it bogs 1/2 throttle

the small hoses are fuel bleed linse and they reurn unused fuel that puddles in the reed plate. the carb. feeds both cyl. evenly thru both sets of reeds if compression is even, then rings are fine. rebuild carb and install mercury gasket set part # 1395-9761-1. this should almost be automatic for anyone buying a used engine unless it is demo on your boat in the water. if and engine sits for more than 3 weeks in a warm climate- ,IE. florida all year or 6 weeks anywhere else during the summer monthes. - fuel will dry in the carbs.
 

Floridian

Cadet
Joined
Nov 15, 2002
Messages
12
Re: Just got 93 20HP merc and it bogs 1/2 throttle

Jamar,<br />My problem was a bad STATOR. I got it back today and it runs great.
 

Jamar

Petty Officer 3rd Class
Joined
Sep 4, 2002
Messages
88
Re: Just got 93 20HP merc and it bogs 1/2 throttle

Test drive proves no change, stil lbogging down. Guess she'll go to the shop this week for a carb rebuild.
 

mellowyellow

Vice Admiral
Joined
Jun 8, 2002
Messages
5,327
Re: Just got 93 20HP merc and it bogs 1/2 throttle

try tapping on the side of the fill bowl with but<br />end of screwdriver. might be a sticking float.<br />carb rebuild is the way I would go... also replace<br />fuel pump diaphram while yur at it and if 1 hose<br />is cracked/split, the rest are not far behind.<br />replace hoses as well. get a manual and you should<br />be able to do yourself.<br />good luck,<br />M.Y.
 

Jamar

Petty Officer 3rd Class
Joined
Sep 4, 2002
Messages
88
Re: Just got 93 20HP merc and it bogs 1/2 throttle

Sorry for teh delayed update. Carb rebuild did the trick.....back on water, runs great!!! Thanks for the help everyone.
 
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