Merc. 50hp 4 stroke motor problems.

[masssilversrt4]

Motor ran good last year.. I put in stabil over the winter.. with a full tank of gas. This year I have been out 3 times with the boat and twice have had issues. I've just recently started fishing salt water with it. 1st issue was motor just died and wouldn't start back up.. it would crank and start to fire then it would just die. got the boat home put the muffs on it and started/ran fine..

Today.. Went out to the salt again.. motor fired right up. Making our way out to our fishing spot 1mi or so.. full throttle motor just dies.. Start the boat back up would run from 15 sec to 2min and then just die again.. so I turned the boat around and got back into shore..

Brought the boat home hook up the muffs and start/runs fine ...

Anyone know what type of problem this could be.. (overheating?? ) Bad gas.. Not sure about the gas because when I run it at home with no load(muffs) it runs fine..

This is on a 1995 Mercury 50hp 4 stroke. boat is a 18 foot tracker.

Any help would be appreciated.

[Ann-Marie]

It sounds like it is shutting down on high temperature.  That is why it works fine at home after it cools.

It could be actual high temperature or a faulty high temperature thermostat shutoff.  

You should locate the thermostat(s), remove them and have them tested.  I put a meter across them and drop them in a pot of boiling water.  They should open or close.  However some modern engines may use a thermisitor and digital high temperature detection.  If that is the case you may have to get them checked professionally or just try a new replacement.

Check your raw water flow.  Clear any input filters.  Make sure water is flowing through with your muffler.

Check for mud dauber wasps filling up the inviting spaces between the air cooling fins on the block and heads.  Honda engines are notorious for this.  They have an additional air filter that looks like a perfect honeycomb wasp condominium.   Make sure you have some fly-screen mesh stuck in the engine cover air intake hole(s).

[Way2slow]

Over temp will give an alarm so I seriously doubt it's over temp.  It sounds more like a fuel or electrical problem but I know very little about black motors and have never seen under the cover of their four strokes so I'm not even going to try and guess your problem.

A fuel starvation problem will usually run all day on the hose but not on the lake.  Without the motor under a load, it's only taking a few percent of the amount of fuel to make rpm that it takes when pushing the boat.

The nice part about it being a four stroke, the dealer is about the only one that's going to have the computer interface to check it out.

I would replace the fuel, make sure it's getting good fuel flow from the tank to the motor and change the filter.  If that doesn't work, be prepared to spend the big bucks and be without it for a few weeks.

[masssilversrt4]

Thanks for the info.. I replaced the fuel filter today.. I'm going to try to get it out this week and try it..