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87 Mercury 115 outboard

R

Robbin

New member
What is the idle setting (RPM's) for this motor? also, engine will idle when prop is disengaged, will rev up but when going from neutral to fwd or reverse, motor dies. Have to go from up-idle to fwd or rev in a very quick motion. Any ideas? Thanks!
 
First I would check to make sure it is firing on all 6 if they are may have a carb problem. Has it been sitting up for any lengh of time?
 
Plowboy, boat sat outside for 4 yrs. Bought last year and replaced all wood. Used boat about 5 times last year. Stored in warm garage during winter. Replaced fuel and plugs last year but did not touch carbs.
 
If motor sat with fuel in the carburetors for 4 years then there is a good chance that there is blockage in the carburetors.----This must be inspected / corrected or serious damage to the motor can occur.-Always run fuel out of the carburetors when taking boat out of the water !----There may be other problems as well, do a compression test and proper spark check.
 
I'd go with varnished carbs for sure. The bowls will tell the story. Berryman's Chem Tool at most auto parts stores is in that business big time. I'd say the main areas of concern would be carbs, especially the bowls where the fuel is stored, and the fuel tank, also where it's stored...dirty tank, strainer etc. In my opinion, the rest of the system would drain in either direction and wouldn't necessarily be a problem.

A fuel pump diaphragm might fail.

If it sat for that long, while you are getting her fixed, drop the lower unit and inspect the fuel pump. The impeller probably has a set and may have brittle blades, both of which are problems. A new rubber impeller is hard but resilient (new rubber feeling) and the blades are strait and radial, no curves or pieces missing or any of that. If the water pump cover and bottom plate aren't scored all that much then you only need an impeller. Otherwise a whole new pump....not cheap.

Then while in the lower unit, drain and refill the lower unit oil using oil designed for outboard lower units and on that engine I would use the premium or high performance oil (personal choice). Get a quart bottle with the hose and pump. Makes it easy. Get new gaskets for the fill and drain screws while you're at it. Old oil should not be milky, or coffee colored. If using Merc Quicksilver oil it will be blue black. If the lower screw, the drain screw has a magnet in it there will be some iron filings on it. Some are ok. Lots could mean excessive wear.

A few places to start.

Mark
 
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