1980 Mercy 50 hp Loses Power

[tbdiver20]

I have just purchased my first used boat and am having some issues with the motor. Firstly we checked compression before heading out the first time and all 4 cylinders were around 80. Is this to low? Secondly when we were out on our first run the motor ran great for about 15 mins at full throttle then lossed power, didnt cut out or stall but the throttle was all the way forward an there was no power left, it never stalled, just kept running at a much slower rate. I have checked the fuel lines the seem to all be fine. The priming bulb looks pretty worn but doesnt appear to be leaking. Any help suggestions or advice would really be appreciated. thanks everyone..

 

[Faztbullet]

Re: 1980 Mercy 50 hp Loses Power

I would try a different guage as 80 is pretty darn low for that engine.

 

[Orbit Express]

Re: 1980 Mercy 50 hp Loses Power

With a motor like that you have to be carefull. Speed away from the dock feeling good, leaving your troubles on land, next thing you know, motor poops out, and you can't get back. Make sure you load the boat with beer next time you go out. Typical Merc's.
Your primer bulb probably has a pin hole.

 

[tbdiver20]

Re: 1980 Mercy 50 hp Loses Power

thanks very much Guys, I'll start by changing the primer bulb and see what happens, on a side note the boat originally had an 80hp on it, same year, 10 mins out from shore "pop" and that was it motor was toasted, they put this on as a replacement. is there any way to get more out of the throttle? there is a big deadspot when you go forward and you have to push it a long way down to get to full?

 

[Solomon Shaffer]

Re: 1980 Mercy 50 hp Loses Power

Those numbers do seem pretty low. If another gauge has a better reading, check the jets...they can get plugged pretty quickly and keep the motor from opening up. One time I jumped a wave and the motor cut from WOT and ran at about 1/2. A piece of gunk had "jumped" into the jet.

I had an old 50hp (1971) that had the same issue with the controls. You had to really press hard at the end to get full RPMs. I'm guessing that you could adjust them.

I know Orbit Express has had a bad experience with a Merc, and I'm not a Merc-only guy...but they do make more motors than anybody else. I'd say that 75% or more of the motors I see on our lake are Mercs...all their motors can't be junk. And besides, we are talking about a 30 years old engine! How many 1980 cars are on the road in great running condition?

 

[tbdiver20]

Re: 1980 Mercy 50 hp Loses Power

Thanks everyone i really appreciated the help. Any idea what compression numbers should be?