1989 Inline 6 Mercury 115 hole by #1 plug ???? rough running problems.

RandyJ

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What, if anything, is supposed to go in this little hole by the spark plug? I'm replacing the water jacket cover gasket. Just got this old boat and it's squirting water on the plugs. I've cleaned the fuel system COMPLETELY and am about to clean the carbs again. When it is running decent for a couple of miles it hits near 50 mph on my gps. Sometimes it does this but can hardly get above idle for a while then ZIP! It takes off like a rocket. Hopefully I've got all the trash out of the fuel system this time....
 

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RandyJ

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okay... I've spent a lot of time this afternoon cleaning everything up and ready to put the water jacket cover back on. Kind of strange to me that there are two gaskets in the package. Am I supposed to put BOTH gaskets on or are they just very skeptical and put two in a package because they have a lack of confidence in mechanics? Why 2 block cover gaskets?
 
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racerone

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???---They sell some common gaskets 2 at a time !!---Just use 1 gasket.
 

pyro225

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Randy, do me a fovour and take some pic of what you are doing, an the bits - i have the same job coming up... cheers
 

RandyJ

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Randy, do me a fovour and take some pic of what you are doing, an the bits - i have the same job coming up... cheers

Seems that I ran into something like this several years ago and it had one gasket glued to the cover and the other glued to the block. So.... that's how I ended up using the gaskets..... as for "bits" not sure what you mean. As for that hole by the sparkplug I've seen it on other motors but don't have a clue what it is for. I've got several other motors I'm going to look at to see what the deal is with them.
 

emckelvy

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As I recall that hole may be a mounting point for a temperature sensor. Which is pretty much useless, anyway. By the time you get a reading on a temperature gage that a catastrophic failure has occurred, the motor is already toast!

Water pressure gage is a much more reliable indicator of the health of the cooling system.

Back to your gasket, as the O.P. said, sometimes gaskets and other "consumable" parts are sold in multiple increments, to save money on packaging/stocking. Sometimes there are more gaskets in a kit than you need, 'cause it's cheaper to throw all the gaskets needed to cover multiple models than it is to have a separate set for each model.

Many of the older Inlines didn't have the temp gage hole, instead the hole at the #1 cylinder spark plug "pad" was round instead of oblongated.

If you were to use the round-hole-gasket on the above motor, it'd probably leak if the gasket didn't cover the entire area (and vice-versa).

At any rate, only one gasket is required, use the one that fits the cover configuration.

If you find the spark plug pads are eaten-away from corrosion, clean 'em up and use a bit of non-copper RTV. Hi-Temp Red works just fine. As does Ultra Black or Ultra Grey, for example. But the Ultra Copper isn't recommended, due to the potential to set up an aluminum-copper-aluminum sandwich corrosion cell.

Hope that helps, G'luck with the repair.........ed
 

RandyJ

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Ed .. thanks for your reply and reminding me that using copper RTV sets up the dissimilar metals scenario. Other than being a shade tree boat mechanic I'm also a plumber and we have to consider that in dealing with plumbing as well as occasional electrical jobs. As for this boat.... I like it so much I'd love to keep it since I've never really owned a fast fancy bass boat that actually looks and runs good... but these jokers suck gas really bad. I've only got 20 boats now and 10 jet skis... all are projects and subject to being sold...really need to sell to clean up my yard. Looks like Sanford & Son lives here.
 

RandyJ

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Still having issues... when I first got it all back together and put it in the water it ran great. Top end is very good.... it is very easy to get started. Put in gear it dies unless I rev it up then slam into forward... frequently dies when I put it in forward or reverse. Once I get it going it is very sluggish then suddenly BAM! It takes off like a rocket.... had this to happen before with other boats and don't remember what I did to fix it... maybe fuel pump or air leak?????
 

RandyJ

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I was going by what the previous owner told me... actually it is a 1984 not a 1989...
 

Chris1956

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Sounds like your carbs are dirty, out of tune or both. The idle mixture setting is a bit tricky. It must be rich enough to allow smooth acceleration, but lean enough to idle well. Start all idle mixtures screws at 1-1/2 turns out from seated. Adjust them 1/8 turn open at a time, top carb first, followed by mid carb and them lower carb, testing between each adjustment. Motor must be warm and in the water in forward.
 

gm280

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I have to completely agree with Chris1956 on his assessment of the carb(s) being your problem. Once you get pass the idle circuit, the high end jets take over and off you go. So buy the carb(s) rebuild kits and disassemble them and clean and rebuild. JMHO!
 

RandyJ

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Thanks guys... I fixed part of the problem when I realized I put the jets in the opposite places they should be. The big one goes in the top and the small one in the bottom... IOW... .074 goes in the bottom and .094 goes in the cap over the bowl/float. The idle screws were originally set at 1 5/8 turn out so that's the way they went back in. Now it starts with a bump of the switch, idles great and top end is still strong... but still got that slow take off and rocket launch start... I've only been through these carbs 3 times before finally getting the fuel system clean an no more trash showing up in carbs. I received new 18-7021 kits yesterday so looks like I'm going to take one more shot at a more proficient cleaning and tuning.... good practice has made it a 15 minute job to remove all 3 carbs and I'm a zip tie expert! Kinda wondering if I should go ahead and put new kits in the fuel pump too. It pulses good but not sure it is doing what it should... not sure how to check that.
 
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RandyJ

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I'm back to tinkering with this boat again. With clean spark plugs Top end it runs great and will idle fine for a while. I can run all day long wide open with no problem. When I try to idle or run slow for much time at all it will foul the spark plugs. I'm assuming the idle mixture screws are causing it to run rich. Any other possible problems that would cause an old tower of power to foul plugs every time you put it in the water? I set the idle screws at about 1 1/2 turns out then tinkered with them from there. They're a PITA to get to and with motor running they're really a PITA.
 
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Chris1956

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If you are fouling plugs at idle, it is likely the carbs are flooding. Check float condition and height. Inspect (or better yet) replace inlet needle and seat. some motors use a brass washer under the inlet needle seat.

The idle mixture adjustment is tricky to get just right. Mix a fresh tank of 50::1 fuel and take an hour to set them properly, on the water, ideling.
 

RandyJ

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Thanks! I've been through these carbs so many times they need a zipper on them. I have replaced everything in a kit and needles. Sounds like I need to take a closer look at the seats. I took it out today... ran across the lake then it ran out of gas. Put new gas in and it was a pain to get home chugging, dying, restarting, then chugging along again. At first it started up and ran slow then POW! Took off like a rocket then ran out of gas and died... new gas and it didn't want to run right so obviously when it ran out of gas that solved the flooding issue...
 
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jimmbo

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From 1984 till 1998 I too had a 84 115. Every so often it would do the flooding routine. For some reason the floats would get stuck in the chamber and not rise. Usually a few love taps to the carb body would free them up. I remember a few times I had to take the fuel bowl covers off and rock them back and forth to free them. Bowls were clean as were the floats. Never did figure out my they would jam up.
 

kingskid7

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I just bought a new cylinder block cover gasket on ebay. the only place I could find single gaskets. I have a 1984 115hp mercury tower of power also. kingskid7
 

jimmbo

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No Title

photo242217.jpg attach10173028.jpg You have to remove the cowl supports, then you can reposition the lower cowl
 
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