1996 Mercury 115 hp won't rev when in water

newt5005

Seaman
Joined
Nov 15, 2004
Messages
51
Hi- motor and year as stated above. Sitting on the back of a '96 24' Pontoon boat. Purchased recently, old owner admittedly had not used in a couple of years. Started right up with a fresh battery on gas that was in tank, so it hadn't been forever since it ran. Continues to start right up, idles fine, revs well on a hose, changed all 4 plugs, which were only slightly used. Changed the gas mix out with fresh and switched to semi-synthetic oil.
Took to the lake and had trouble with it staying running after putting it in gear. Continues to start well, just dies when putting it in gear. After feathering the throttle to keep it running, cannot get to 3,000 rpm's. 2800 is about it, max speed (GPS) is 12. I checked, and WOT should be slightly north of 5,000. I wasn't planning on going that high, but seems something isn't quite right. I ran it for around a half hour at 2500 to 2700, stopped for an hour or so (lunch, swim) and headed back, another hour or so.
I know the new fuel is now well cycled through the carbs. Time for the shop? I'm fairly mechanical but at this point, don't have a direction.
Thanks in advance.
mike
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,047
Start with a compression test.-----------Then look for strong spark on all 4 cylinders.----Is the automatic oiler bypassed ?
 

Fleetwin

Lieutenant Junior Grade
Joined
Nov 23, 2011
Messages
1,141
You are not getting power from all four cylinders.

Compression.
Carb
Spark
 

newt5005

Seaman
Joined
Nov 15, 2004
Messages
51
So... first of all, I guess my brain was scrambled during my original post. NOT a 115hp, it's a 120hp. Different engine? donno. I was accurate with the 1996 year, my apologies for the incorrect info. It's a Merc, marketed as Force, not a Chrysler.
Now, the next hiccup. When pulling the cover off, I found the #4 plug wire laying on the deck, so I think I found part of the problem. On to the compression / spark results.
Top down, I'm assuming #1 is always on top (no pun intended)
#1- 145
#2- 160
#3- 165
#4- 160
I'm just outside the 10 % rule and decent numbers, so I think this looks good.
I picked up a glass spark gauge and the spark shows consistent lavender color on all 4 holes.
I am assuming it was never oil injected, it has no oil tank or related components.

Next step??
 
Last edited:

racerone

Supreme Mariner
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Dec 28, 2013
Messages
36,047
It is a FORCE marketed by Mercury.------A glorified " updated " former Chrysler model.
 
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