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Blue Band Mercury issue 1988 80hp

jim_bo

New member
Hey,

I have a 1988 Blue Band 80hp 4 cyl mercury engine.

The engine starts fine, revs fine when loaded up out of gear.. But when you put it into gear and go full throttle, it won’t go any faster than about 5 knots and will hold that speed consistently.. It won’t go any faster..

The throttle arms appears to reach max and min in the engine when applying the throttle..

I did find a fuel leak around the filter housing, replaced the O ring and stoped it sucking in air, but it appeared to make no difference.. I guess the leak started after the initial problem.

Any ideas on where the problem could be?

Thanks
 
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Re: Blue Band Mercury issue

Firstly I think you are a wee bit out in the year as the stopped the blue band around '78.Post the number on the motor and someome will be able to give the year.
I think a carb rebuild is in order as it sounds like a blockage somewhere.
 
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Re: Blue Band Mercury issue

Yer sorry its ment to be 1980.. I will get some info off the engine once the rain stops..

I was thinking more along the line of spark plugs, can they cause this kind of issue, maybe not firing on all cyls? any other quick things to try before a carb rebuild?.. It apeard to work fine one day, then a few days later with the next use the broblem was present..

With the muffs on it really does sound like its reving at full revs in gear, but I couldnt be 100% sure if thats the case
 
Re: Blue Band Mercury issue

I can only find a serial number.. There is a white sticker with timing information thats starts with 1980..

Its a 4 cyl.
 
Re: Blue Band Mercury issue

OK Start with a compression test,look for a bout 110-130 psi down the line with no more than 15%psi of difference.Check for spark on all cyls.Do not rev past 1500rpm on muffs,put it in a tank.If the plugs haven't been changed in sometime,change them.
I have just reread your post,is it reving but not making speed?
 
Re: Blue Band Mercury issue

Compression tested and came back consistant 130 across all four cyls. At a glance plugs look fine, they look fairly new, but I guess doesnt mean one or two arnt faulting.

Its not over reving, it apears to be reving at a fair pace for the 5 knot top speed.. But out of the water it apears to rev high in and out of gear.

"Do not rev past 1500rpm" not that I have thrashed it with the mufs on for more than few seconds I didnt kno that.. thanks.

When I tested it a guy at the ramp said sounds like plugs but went on about them being glow plugs as he has an older version.. Im pretty sure they not glow plugs?
 
Re: Blue Band Mercury issue

Oh course not--that's for diesels. Is the motor reving up in gear but the boat is not moving well? If so, the prop hub could be slipping.

Jeff
 
Re: Blue Band Mercury issue

Ya thats what I thought re glow plugs..

The prop is brandnew after the issue started as old prop was rather warn.
 
Re: Blue Band Mercury issue

I still go with the fuel restriction.Check along the fuel line from tank to motor and I would suspect the carbs need rebuilding.
 
Re: Blue Band Mercury issue

I have allready made a new hose from fuel tank to engine.. Carb rebuild sounds like a major :(
 
Re: Blue Band Mercury issue

Only the first time:D. Get a manual can be got of Andrew who runs this site,take lots of pics,don't put any of the plastic components in the carb cleaner,and most importantly,take your time.:)
 
got a similar prob,engine starts up on high revs,but when you drop the lever back down it cuts out,noticed a small fuel leak from the top of the 1st carb,and the fuel line bulb goes soft, its a mercury 4 cyl, 2 stoke,no id plate,no 10178359 or xk76540 if thats any good,engine has been idle for 2 years
 
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