Looking for help with engine problems

[Coomes4]

Looking for some help/advice with my engine problem.

2002 Yamaha 50hp 4 stroke

Forgive me in advance, as i'm a weekend warrior that sadly uses my boat about 6 days per. I'm not mechanically inclined, i'll describe as best as I can.

Starting the boat - turn key, chugs but doesn't fire. I engage the neurtal button (in middle of my hand throttle) push throttle about 1/4 way and turn key. Engine starts right up.

Move throttle back to neutral position, the engine seems to be "shaking". Not a violent shake, but it is noticible.

Engage the throttle in reverse, it works properly.

Engage throttle in forward, it seems to work properly until i push it past the 1/4 range. Then the engine simply stops. Rinse and repeat, same results.

It seems as if only 2 or 3 cylinders are firing, I put new plugs in today.

The gas might be an issue, as half of my tank is roughly 12 months old and the other half was put in yesterday. I put 1/2 can seafoam in, doesn't seem to help.

Thanks in advance.

[BigTom]

Looking for some help/advice with my engine problem.

2002 Yamaha 50hp 4 stroke

Forgive me in advance, as i'm a weekend warrior that sadly uses my boat about 6 days per. I'm not mechanically inclined, i'll describe as best as I can.

Starting the boat - turn key, chugs but doesn't fire. I engage the neurtal button (in middle of my hand throttle) push throttle about 1/4 way and turn key. Engine starts right up.

Move throttle back to neutral position, the engine seems to be "shaking". Not a violent shake, but it is noticible.

Engage the throttle in reverse, it works properly.

Engage throttle in forward, it seems to work properly until i push it past the 1/4 range. Then the engine simply stops. Rinse and repeat, same results.

It seems as if only 2 or 3 cylinders are firing, I put new plugs in today.

The gas might be an issue, as half of my tank is roughly 12 months old and the other half was put in yesterday. I put 1/2 can seafoam in, doesn't seem to help.

Thanks in advance.

[BigTom]

Probably bad gas.I work on police cars and have had starting problems due to old gas. The gas we get now begins to go bad in 30 days and is usually useless after 90 days. Always fill up at a busy station, where you will get fresh gas and don't store it too long. On you boat, try a remote tank with fresh fuel and see if this fixes the problem.

Another problem we have seen with this gas is the fuel tank rusting inside due to the water in the gas when the fuel separates. This is only a problem with steel tanks which is the reason most cars have plastic tanks now. BigTom

[welder]

I would do as Big Tom says and get rid of the tank of fuel you have now , clean the tank , change the filters and if your a carbed motor you may have to have the carbs cleaned.

Good luck and have a Safe 4th.

[Coomes4]

Update...

I switched out my fuel line to a portable tank. Added a can of Seafoam to the portable tank, in case of possible carb build-up.

Ran the motor on idle for about 45 minutes.

Took out for a test drive, there appears to be performance improvement, however it still won't open up. It doesn't "kill" but it wont get past 2800 rpm.

I'm frustrated and want to row it out to middle of leech lake and perform a sinking.

My guess now is something electrical in the motor.

[Pearl Diver]

"Boating is like deaf dating" You may may acknowledge the problem which is not readily identified, may diligence and commitment be your watchword. Best of luck.Your lack of mechanical savvy will shortly be replaced with an uncanny desire to "fix". I would go with the electrical/water separator theory.....

PD