1985 75HP Merc Help ASAP

[Faubertlx]

OK so i need some help, I have a four cycle, 1985 75HP motor, 2 years ago it was rebuilt, tested then winterized. It was started again today, We cleaned the gas tank, cleaned the spark plugs and it started. Here are my questions

1. Is it 2-Stroke? (we mixed the gas today just to be safe)
2.is there oil I must put in the motor?
3. What about the bottom end lube?
4. I believe it is a 1985! i saw a 1985 on youtube and it looks the same


Here are the issues im having, It will not idol, I must use the throttle to start it, then i can quickly put it in gear and take off, if i try to go above half throttle it dies, in order to bring it to full i need to tap the choke on the key then it will run clean.

So any help or Advice for me would be great! thanks for all your help!

 

[redjmp]

Re: 1985 75HP Merc Help ASAP

It is a 2 stroke that needs oil mixed with the gas. 50 to 1.

The bottom end is gear lube. ~90W. It should be checked every year and replaced if found to be milky as that is a sign of water contamination. The marine rated stuff is better if you have leaky seals as it has an emulsifier that absorbs a certain amount of water and prevents your gears from rusting.

You are having fuel problems likely from clogged and varnished carbs.
Try running a can of seafoam through your tank and see if that cleans out the varnish before deciding the carbs need to be overhauled.

 

[Faubertlx]

Re: 1985 75HP Merc Help ASAP

Thanks Redjmp! Thanks for all the help! Im gonna try the sea foam! We we definetly not running 50:1 mix, we were not sure if it was 2 or 4 stroke so we put some oil in there just to be sure! So i dont know if the mix could have caused that becuase my buddy who knows some stuff about boat motors said its not getting enough fuel since we need to choke it to get it to go. we did not clean the air filter either, Today im going to go get some sea foam and bottom end oil and give this another shot! thanks for all your help

 

[Texasmark]

Re: 1985 75HP Merc Help ASAP

What air filter? I had an '84 85 hp, cowl had a red, blue, and silver (I think) stripe down the side which went left to right, but at the rear of the cowl all 3 stripes fell off and pointed down...did not continue around the back.

Anyway, it was 2 cycle; didn't think Merc made a 4 cycle OB for roughly 20 years later.

Anyway a pint of Bia certified TCW (TCWIII nowadays) 2 cycle oil treats 6 gallons of gas.

There is no air filter on that engine if like mine and probably was. There is a black box over the front of the carburetors used for tuning the air intake and silencing the carb sucking sound at high rpm's....so don't worry about that part....unless a mud dobber made his home in there and down here in Texas, that can and does happen.

Yes on the can (pint) of sea foam (at most auto parts stores in a white and red can) and why not the whole can, but still put in a pint of the 2 cycle oil and then fill the tank. If you can't get a full 6 gallons in there, get what you can.

Back in the 50's the mix was a quart of oil to 6 gallons so if you have too much oil it will smoke and maybe foul the plugs if you don't get it out and run it, but it's better than being low on the oil ratio.

HTH

Mark

 

[aussieflash]

Re: 1985 75HP Merc Help ASAP

Best thing you can do is post your Serial number(stamped on block or transom bracket).then we can locate your engine model.Then you should get the manual for that model....Mercury,not the other rubbish.
Now if your boat runs good when using choke,I would be checking your fuel pump first.Good luck.

 

[Faubertlx]

Re: 1985 75HP Merc Help ASAP

Im going down to the boat and Ill get the serial number for you!

Ok so here is the update- It ran good for a while yesterday with the sea foam, But the issue we were having yesterday is that the motor would run beautiful on the fast throttle, as soon as we went to put in gear it would go into gear and i could bring the throttle up just enough then it would die, that happened about 6 times. After doing that we got it to idle in forward around the pond. then i was able to bring it up to half throttle by taping the choke to get it there, then i got it up to full but it did not go even close to full speed, so i stopped and quickly did the fast throttle, but this time when i raised the fast throttle it jerked it self in and out of forward. now after that i have no reverse (just the throttle functions in reverse) and in idol it keep trying to slip into forward. I dont know if the throttle cable is messed up or what. By The Way! i did not hold the fast throttle up for long, i have had many speed boats, I know how NOT to blow them up! Thanks for all your help!