Mercury 115hp stalls-in gear

[ttriebler]

Have a 1976 Mercury 115hp outboard - the in-line 6 with thunderbolt ignition.<br />Motor starts fine and revs fine in neutral.<br />When put in gear it stalls. Occasionally I manage to get it in gear without stalling and it gradually picks up revs and then runs fine. Back into neutral and it slowly stalls. Still easy to start and compression is good on all cylinders.<br />The boat shop told me that the labrynth seals have gone in the motor which causes this problem......how does one check, what are labrynth seals and where are they located? How easy/expensive are they to fix?<br />I was hoping it might be something a little less dramatic such as a pinhole in the fuel pump diaphragm. Have replaced all fuel hoses outside and inside motor and cleaned all filters but have not yet done the pump as it seems to go well at WOT.<br /><br />Any help would be greatly appreciated.

 

[greasemonkeyozi]

Re: Mercury 115hp stalls-in gear

You can get a diaphram kit with all gaskets for about $5.00 at your local dealer. When was the last time you know of your carborators were rebuilt?<br /> Look at your fitting that connects the fuel line to the motor itself. Take a look inside it and see if it has a rubber O ring inside it. Cut it off on the line and go to Wal mart and buy another one just in case that O ring has dryrotted causing air to get into your fuel system.

 

[Gold Bear]

Re: Mercury 115hp stalls-in gear

toddski <br /><br />The idle mixture is too lean. On all three carbs, lightly seat the idle mixture screws then open them about 2 turns. Once the boat is in the water (you can't adjust this using muffs) test the motor to see if it "stalls" when you put it in gear and try to accelerate. If it does, open each screw another1/4 turn until it quits stalling.<br /><br />I have a 1971, 115 that likes 2-1/2 turns open.<br /><br />Good Luck,<br /><br />Gold Bear

 

[The Marine Doctor]

Re: Mercury 115hp stalls-in gear

To check the Labrynth seals. Either run the engine at 25-1 or spray some oil into the carb. If the engine idles, you have found your problem.<br /><br />I would also look into replacing the restrictors underneath the intake ports on the side of the engine.<br /><br />TMD

 

[ttriebler]

Re: Mercury 115hp stalls-in gear

OK thanks for your feedback so far. I ran the enginge on 25 to 1 fuel this morning but it's not idling any better. So it might be good news about the labrynth seals.<br />Have checked the o-ring on the fuel line going into the engine and it's A-1 condition. Also cannot see any air bubbles in my glass filter coming out of the tank so air leaks seem unlikely.<br />I would like to try adjusting the idle mixture screws as suggested but don't know where these are located on the carbs. Can you give me some directions please.<br />I'll let you all know if this helps things along a bit. Thanks heaps.

 

[The Marine Doctor]

Re: Mercury 115hp stalls-in gear

Idle mixture screws are on the front top right of the carbs.<br /><br />If this does not fix the engine. You will likely need to replace the restrictors that are under the intake ports.<br /><br />TMD

 

[Gold Bear]

Re: Mercury 115hp stalls-in gear

The Marine Doctor <br /><br />Tell us a bit more about the restrictors. Is this a part that you can easily get at the local Mercury dealer? What do they look like. How involved is it to replace them? Just what is it that they do? How can you tell if they need replacing?<br /><br />Isn't there not one at the lowest cylinder (seems like I heard someone say that before).<br /><br />Regards, <br /><br />Gold Bear

 

[ttriebler]

Re: Mercury 115hp stalls-in gear

Thanks for the advice. I screwed the idle mixture out 1/2 a turn on each carb today and it no longer stalls!! Woohoo!!<br />There seems to be quite a difference in neutral idle rpm and in-gear idle rpm though - may require further invstigation.<br />I cannot supply more information until I get the tachometer working. Anyone know how to test the tachometer pulse? I have a VDO 7,000 rpm tacho and have connected positive, negative and pulse but she's not moving.

 

[The Marine Doctor]

Re: Mercury 115hp stalls-in gear

Gold Bear<br /><br />The restrictors are plastic inserts that are placed in the intake ports to control the amount of fuel that is bled off the cyl.<br /><br />#1 flows down to #2 and so forth.<br /><br />If the restrictor is gone..it will flood the cyl below it with excesive fuel.<br /><br />Part number is 66517 Inline 6 engines have 5 of them and there is not 1 in the bottom as the fuel just flows out the exhaust.<br /><br />TMD

 

[Gold Bear]

Re: Mercury 115hp stalls-in gear

The Marine Doctor <br /><br />Thanks Doc!<br /><br />Best Regards,<br /><br />Gold Bear

 

[ttriebler]

Re: Mercury 115hp stalls-in gear

Marine Doctor,<br />Thanks for the info on the restrictors. How do I get a look at them to see if they are intact and check for wear?<br />thanks<br />Toddski

 

[The Marine Doctor]

Re: Mercury 115hp stalls-in gear

The restrictors are located under the intake ports, on the starboard side of the engine. The port covers have long heatsink fins on them and there are 3. They are held in place by 7/16 bolts. <br /><br />The covers run the length of the motor.<br /><br />TMD