1989 Mercury 60hp Running Problem - Please help.

E30Adam

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Aug 9, 2010
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Hi everyone,

I'm having big trouble finding out the source of a problem that I'm having with my engine. I've got a 14ft Fletcher Arrowflyte GTO speedboat that we use for doing a bit of wakeboarding. The engine is a 1989 2-stroke Mercury 60hp, 3 cylinder outboard.

The engine is fine when out of gear and when using flush muffs on the engine but when the boat is in the water and full throttle is applied, the engine struggles to pull. The trouble is, the problem comes and goes for no apparent reason.

So far I have changed the plugs, changed the inline fuel filter, changed the primer bulb, removed and cleaned the carbs twice. Last time the problem occurred, I removed the plugs whilst out at sea and simply wiped the ends with my finger and replaced. The engine then seemed to run fine. The only difference between the 3 plugs is that cylinder 1 seems to be a little black on the white ring of the plug. They're NGK BUHW's which I've confirmed is the correct plug type.

We are also using 2 brand new plastic fuel tanks and have switched between the two which makes no difference. I have also dismantled the fuel pump which looks ok to me, nothing appears to be out of place or broken.

I'm using a 50:1 2-stroke mix and have checked that the breather vents are open on the tanks.

I've uploaded a video to youtube so that you can see exactly what's happening. Please bear in mind that the throttle is at 80% and is not being adjusted for the duration of the video.

http://www.youtube.com/watch?v=l_viou7lUeM

Please please help as this is getting really annoying and I'm on holiday at the moment and cannot use my boat!!

Thanks in advance.
 

latin monkey

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Jun 5, 2010
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Re: 1989 Mercury 60hp Running Problem - Please help.

have you checked the compression?
 

latin monkey

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272
Re: 1989 Mercury 60hp Running Problem - Please help.

i would rebuild the fuel pump with new a diaphram and check valves. it seems to be a fuel problem to me. have you adjusted the mixtures on the carbs?
 

E30Adam

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Re: 1989 Mercury 60hp Running Problem - Please help.

I haven't checked compression. I have a compression tester, I presume it's the same as a car engine? Remove all leads and take one plug out and fit tester. Turn engine over a couple of times then take reading and replace plug. Repeat with other plugs.

Can you buy a kit to rebuild the fuel pump or is it just the diaphragm I should be changing? It certainly looks like it's fuel related somehow!!

I tried adjusting the mixture but it didn't really help. It's set at 1 1/4 turns out which runs nicely when the problem isn't there. I changed it to 1 1/2 turns out as recommended by someone I phoned but the engine didn't run so smooth and the problem started again.
 

latin monkey

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Re: 1989 Mercury 60hp Running Problem - Please help.

take all the plugs out and check compression and let us know what it is. the fuel pump kit will have a new diaphram but some don't have the check valves. just find the one that includes them
 

Kinloch

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Aug 1, 2010
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Re: 1989 Mercury 60hp Running Problem - Please help.

am having similar problem with '04 3 cyl 2 stroke, very low hours
have flushed carbs (twice), replaced fuel lines and filters
compression fine
when i pull the air box off, there is oil rich fluid laying in bottom of each carb
any thoughts? idles a little rough, but smoothes out with throttle no load, cuts out in gear with throttle up
 

latin monkey

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Jun 5, 2010
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Re: 1989 Mercury 60hp Running Problem - Please help.

try adjusting your carb mixtures
 

E30Adam

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Aug 9, 2010
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Re: 1989 Mercury 60hp Running Problem - Please help.

take all the plugs out and check compression and let us know what it is. the fuel pump kit will have a new diaphram but some don't have the check valves. just find the one that includes them

I did the compression test today and all 3 cylinders read 10bar with no drop in compression. I haven't gotten round to getting a fuel pump kit yet though.
 

latin monkey

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Jun 5, 2010
Messages
272
Re: 1989 Mercury 60hp Running Problem - Please help.

i had to look it up in a conversion table but that compression is very good :)
 
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