1979 Merc 90hp Throttle issues??

Hey all! I am new around here and would like to start off by saying hello!

I just bought a used GREW 163 runabout w/90hp merc 2 stroke o/b and had it out yesterday.. It started and ran like the thing was brand new. My issue is that, after I had turned the boat off and came back after 5 mins to go for another rip, I had ZERO throttle?? The engine would start very easily and would go into gear (FWD and REV), just no power to get moving... after awhile of trying to get my boat to my trailer on the power I was getting in gear only, my engine started stalling.

I need to point out that when the boat was performing well, I had run out of gas and switched my gas tank to my back up. The tank was 25l/5.5g and I had put in 500ml of 2 cycle into it as Merc calls for a 50:1 ratio, but I fear that I did not mix the two well?? As a matter of fact, I just poured the oil in with that gas and that was it.

I am very much a newb and expect a flamming but I would really like some insight to the disaster that may be ahead of me.

Thank you!

Re: 1979 Merc 90hp Throttle issues??

Anyone??

It is a merc 1979 900 6 cyl 2 stroke with 3 carbs..

I have checked the linkage at the engine and the trottle linkage is moving through it's range, from what I can see.. The carbs do not seem to open when engaging the throttle? (Could that be the issue?)

I am very new to engines of any type, so any info or troubleshooting tip's would help me out greatly.

Re: 1979 Merc 90hp Throttle issues??

Most of us are on the US measurement scale, so bear with us.

OK, 500ML is 1/2 liter which is about 1 pint, which is correct, so the mix is good. That motor should have a distributor. When you push the throttle forward, the distributor should turn and a finger will open the top carb. The other carbs are connected to the top one, and open with it. see if that is happening and post back.

Re: 1979 Merc 90hp Throttle issues??

Thank you for the reply.

I have checked all what you have requested and no, the distributor is not turning and nothing is engaging the finger that opens the carbs. When I move the throttle, the linkage that is connected to the leg is the only thing moving.. I see there is a linkage that attach to a control arm that goes up to the distributor, there is zero movement here. I have tried to manually move it with no luck as well.

Please note, when I engage the finger at the top of the carb set up, the carbs are only opening about a 1/8 of an inch.. Is this normal?

Re: 1979 Merc 90hp Throttle issues??

With the motor OFF, have a helper shift into gear and open the throttle all the way while you watch both cables on the motor.

I expect you will see only one cable functioning, which would lead me to think either the throttle cable has broken or there is a problem inside the control box.

My money is on a broken cable.

Re: 1979 Merc 90hp Throttle issues??

CharlieB said:

With the motor OFF, have a helper shift into gear and open the throttle all the way while you watch both cables on the motor.

I expect you will see only one cable functioning, which would lead me to think either the throttle cable has broken or there is a problem inside the control box.

My money is on a broken cable.

Click to expand...

Thank you, I have had my helper do so and this seems like it could be the issue. When I have time later on, I will take a closer look at the controls and cables that enter for wear, breakage or detatchment.

I appreciate the tips guy's! I just need to think alittle more methodically when trying to troubleshoot engine issues... I am really new to this but I am also loving this.. cept for the $$ out. lol! I will update you.

Re: 1979 Merc 90hp Throttle issues??

Disconnect the throttle cable at the motor and PULL on the slide, if it is broken you will soon know it as it will pull out of the sheath.

Re: 1979 Merc 90hp Throttle issues??

thank you! the problem was the cable and I have since replaced it, works great too! all though it took me a bit to figure out how to put that retro Mercontrol back together... :/