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Merc 260 ressurection

79century

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"well l tried to post this las

"well l tried to post this last nite and it must not have taken.
anyway, last nite was my big nite. i fired up my old school 260, 898 outdrive, 2bbl roch. setup.
this is first time since the following work has been done:
-rebuilt carb -rebuilt fuel pump -replaced timing chain & sprockets -replaced harm. balancer since i used wrong puller on old one -rebuilt dist. and installed pertronix conv. and coil. -succesfully welded up hairline crack in intake manifold -replaced plug wires,oil,oil filter,water separator,temp sensor, had impeller replaced and lower re-sealed, added fresh fuel.

2 yrs ago i had the heads shaved and a 3 angle valve job done, and replaced manifolds and risers.

the compression checked good.

boat has sat almost a year and, before that had begun to idle rough and not throttle up at all, so, as you can see, this prompted me to really go through it.

well, i had the idle screws out 1.5 turns and timing in the ballpark. i wen't to fire it up and it started rite up, and i dialed in the timing and it ran better than ever! i still need to tune in the idle mixture screws (in till it goes ruff, then out till it goes ruff then split the difference on each one right??)
i thought that the drain plugs on both sides of the block were rotted out, because i had water running from both of them. but this morning it hit me, there are 2 un-identified brass plugs in the gunwhale of boat. the mechanic that did the lower unit work must have pulled them before cold weather hit last fall. so, after work i'm gonna stick them back in. should i chase those nasty threads with a tap? if so what size are they??
my temp. gauge never read anything after my 10-15 min muff run. -new sensor, i crimped new connector on wire. high quality gauge. how can i troubleshoot this??
now the not so good news, i have oil wettness on the block/head/exhaust manifold above the starter, where all three of these are in close proximity to one another. not dripping but well saturated from just the 10-15 minute test running. i inspected with mirror while running and can't pinpoint leak. could this be something that will tighten up and stop leaking after some run time? i have no water or fuel showing up in oil, and like i said it ran awsome. better than ever, mostly b/c of the electronic conv. i guess. anyway, i'm psyched about getting out there after my near 2 year layup.
happy boating to all and have a safe weekend."
 
""should i chase those nas

""should i chase those nasty threads with a tap?"

No, there is a seat for the plug tip inside.

"...gauge never read anything..."

Is there a T'stat installed? Ground the wire to the block; if the gauge pegs to the maximum it and the circuit is good. If not then check the connectors at the sender and back of the gauge for corrosion.

Did you put pipe tape or sealer on the temp. sender? Remove it if you did. If the sender was not removed it may have a layer of crud on it that can be cleaned off w/800 grit sand paper.

"i have oil wettness on the block/head/exhaust manifold above the starter..."

Check for loose oil pan and valve cover bolts. Is the dipstick in the same location? Clean the area and seal it. Clean off the oil; if it appears again then add oil dye to the oil and use a black light to find the leak."
 
"thanks guy,
there's a th


"thanks guy,
there's a thermastat. i will try grounding the wire when i'm off work later. and see what i get. i did put some sealer on the senser before i screwd it in. i will get that off too. the dipstick is on the other side. i'm gonna clean the area good, and then go for a sea-trial and try to watch it enough to find the source, thank you guy. i'll post the results."
 
The gasket between the thermos

The gasket between the thermostat housing and the inlet manifold should have a couple of brass studs. These studs ground the thermostat housing so the temp gauge sender and hi temp alarm switch get a connection to ground.
 
Good point but many older mode

Good point but many older model engines don't require the studded continuity gasket under the T'stat hsg. since their temp. and alarm senders are in the intake manifold.
 
"yea, mine is definitely one o

"yea, mine is definitely one of the older ones. there are no brass studs, and i don't have a temp alarm. just the gauge., but thank you chris."
 
So where is the temp sender mo

So where is the temp sender mounted ?? If it is in the thermostat housing you will need the gasket with the brass studs.
 
"no, it's in the intake ma

"no, it's in the intake manifold. it's a brass threaded plug type, with one spade electrical connector on top. i cleaned the sealer off of it and threaded it back in. it's new(the sensor). i grounded the wire, and the gauge pegged, so i know the gauge & circuit are working. so could it be the sensor, even though it's new? can it be tested?"
 
"yes, touching the base to a g

"yes, touching the base to a good ground or using a jumper wire to the base of the sender you can put a lighter to the bottom, for just about 30 seconds, should see the gauge move."
 
The sending unit (sensor&#

The sending unit (sensor)Is nothing but a variable resistor. Its range is ~ 80 ohms to ~ 240 ohms

So when cold I think it will measure 240 ohms
(center post red lead and threads black lead)

Put sending unit in a pot of water on the stove and turn the heat up and watch the ohms decrease/increase what ever way it changes I forget. It should rise steady. Keep the center post above the water though.........

If your meter in your dash does not read it correctly it is probably a grounding issue.
 
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