help needed with mariner 50hp 1998 model

[ma160802]

Hi,I have an issue with my outboard and i noticed it about three weeks ago when i went out to bobin head after a day of use. I was driving back full throttle and then suddenly the rev's just dropped from 6000 rpm down to 3000 rpm and it would not rev harder despite having the throttle right down , occassionally while limping back on 3000 rpm it would rev up then straight away drop back down to 3000 rpm. A couple of factors i can think of are i used e10 by misstake about three weeks ago which i drained out since , and i removed the under floor tank when i first purchased the boat about 2 months ago just to drain the stale fuel and clean it out. Im pritty sure its not over heating as i have just done a full service on the boat and replaced the impeller and plugs and gearbox oil about 4 weeks ago.

[kurtisjohnthomas]

Hi,I have an issue with my outboard and i noticed it about three weeks ago when i went out to bobin head after a day of use. I was driving back full throttle and then suddenly the rev's just dropped from 6000 rpm down to 3000 rpm and it would not rev harder despite having the throttle right down , occassionally while limping back on 3000 rpm it would rev up then straight away drop back down to 3000 rpm. A couple of factors i can think of are i used e10 by misstake about three weeks ago which i drained out since , and i removed the under floor tank when i first purchased the boat about 2 months ago just to drain the stale fuel and clean it out. Im pritty sure its not over heating as i have just done a full service on the boat and replaced the impeller and plugs and gearbox oil about 4 weeks ago.

Could be a couple of things.

I would say either water in the motor

Or really dirty fuel filter.

[Guest Aussie007]

drain your fuel hose take both connections off and pour the old fuel out into a clear container so u can judge the results also remove the air filter on the engine and drain the carbies each carby has a screw at the bottom undo the screw and the fuel will drain from the carby make sure to do the screw back up than u should be good to go just remember when u come across this problem again if your lacking fuel to the engine and at wide open throttle u can melt the pistons

[ma160802]

Could be a couple of things.

I would say either water in the motor

Or really dirty fuel filter.

when i had the service we changed the water/fuel separater filter. but there was another filter in the engine that we didnt change.

also last time this happened (surge or loss of power ) i pumped the fuel bulb and it didnt happened again

[daniel944]

Seems more like ignition, based on the comming and going of revs. Is it running on all cylinders when the revs drop? If its a multi carbie engine, could be something like a sticky needle and seat in one, an inspection of spark plug color may help determin this.

[ma160802]

drain your fuel hose take both connections off and pour the old fuel out into a clear container so u can judge the results also remove the air filter on the engine and drain the carbies each carby has a screw at the bottom undo the screw and the fuel will drain from the carby make sure to do the screw back up than u should be good to go just remember when u come across this problem again if your lacking fuel to the engine and at wide open throttle u can melt the pistons

what are you suggesting is the problem? water in the fuel? or dirty? as i have already drained the tank twice now?

When this problem happened last i pumped the fuel bulb when the engine was going and it fixed the problem. any idea?

[Guest Aussie007]

check your fuel pump is working correctly i had a similar problem my engine was running one week the next it wouldnt go over 1/4th throttle later at home i took both ends off of the fuel hose and poured the contents into a clear coke bottle and it was visible i had a clear jelly looking substance in the fuel line which was clogging the carbies

[ma160802]

Seems more like ignition, based on the comming and going of revs. Is it running on all cylinders when the revs drop? If its a multi carbie engine, could be something like a sticky needle and seat in one, an inspection of spark plug color may help determin this.

Im pretty sure its running on all cylinders because it doesnt sound like its missing or lumpy . It just doesnt wont to rev , its like its starving for fuel i think. If i pump the fuel buld it goes ok , it worked the last time i was out anyway

[ma160802]

check your fuel pump is working correctly i had a similar problem my engine was running one week the next it wouldnt go over 1/4th throttle later at home i took both ends off of the fuel hose and poured the contents into a clear coke bottle and it was visible i had a clear jelly looking substance in the fuel line which was clogging the carbies

Well when i drained the tank the second time becuase of the e10 fuel and this problem i pump 60 litres out and i disconnected the hose off the motor and pumped it out using the fuel bulb . The fuel looked ok and i actually used it in my car and lawn mower and there running ok

[tareeterror]

It sounds like starving for fuel, either you have a blockage in filters, line or carbies. or even fuel pump diaphragm has weakened and not pumping enough fuel. start with basics such as filters and fuel tank breather, then maybe pull carbies off and clean fuel bowls and jets out. then check output of pump.

[ma160802]

If this keeps happening could it cuase damage to the motor??

[jimg1au]

i had the same problem with my 70 yamaha changed the fuel pump all good now.if the motor runs when you use the bulb to prime the carbies and stops when you dont then the bulb is doing the job of the fuel pump.

jim

and yes running the motor lean will destroy you motor as

1 not enough lube with fuel/oil

2 engine running hot chance of melting pistons

3 exesive ware from overheating and poor lubrication

[Guest Aussie007]

If this keeps happening could it cuase damage to the motor??

i wouldnt risk the $2000-$3000 your motor is worth to keep running it the way it is u said u ran E10 fuel in a non compatible E10 model i remember reading about E10 fuels and grey fuel hoses not being compatible the E10 fuel would turn the inside of the fuel hose to jelly now this wont be your problem but this is an indication the E10 fuel might have done some damage to your fuel pumps diaphram the rubber is very thin so it might have been effected to the point where its no longer sealing your fuel pump if you run your engine and pump the primer and the engine runs fine than the fuel pump is your problem

[ma160802]

i wouldnt risk the $2000-$3000 your motor is worth to keep running it the way it is u said u ran E10 fuel in a non compatible E10 model i remember reading about E10 fuels and grey fuel hoses not being compatible the E10 fuel would turn the inside of the fuel hose to jelly now this wont be your problem but this is an indication the E10 fuel might have done some damage to your fuel pumps diaphram the rubber is very thin so it might have been effected to the point where its no longer sealing your fuel pump if you run your engine and pump the primer and the engine runs fine than the fuel pump is your problem

thanks for all your help , i have bocked it in for a fuel pump overhaul and to check all hose lines . I hope this fixes the problem.