1981 mercruiser 120 153 cid

[jayandzach018]

hi i am new to this post but i just rebuild my motor and it starts and runs (when it wants to) but this it wont start up so i took off the plugs and one plug #4 was soaked of gas so i took off all the plugs and cranked the motor and only the number 4 was shooting out gas like crazy (new carb not rebuild), so i thought the valves was adjusted wrong so i was playing with the valves and bingo no more gas shooting out of the #4 cyl. so my ? is does anyone knows the gap for the valve or ever did a valve job and why the motor takes a long time to start??? sorry i am new to this.... new tune up kit plugs,wires,cap,roter and point kit and coil, carb is new intake is new. 1981 mercruiser 120 153cid 4cyl

 

[APPALOOSA2]

Re: 1981 mercruiser 120 153 cid

There is more to it than what the clearance is. You have to go through a sequence.
Don has been gracious to put the manual for that 120 online to down load. Yes the whole manual for your engine.

It can be found in "ADULTS ONLY " at the top of the mercruiser forum, yes the one you are in now.

 

[jayandzach018]

Re: 1981 mercruiser 120 153 cid

ya i have the book but i dont think i am smart i mean i know how to adjust the valves on a car but is the boats the same does all the i's have to be .010 and the e's have to be .012 with #1 on dtc and then adjust with a filler gauge?

 

[JustJason]

Re: 1981 mercruiser 120 153 cid

they are hydraulic lifters. They need to be set to 0 lash. I forget if they want an additional turn after 0, but it's in the manual. It's not done with a feeler gauge.

 

[Maclin]

Re: 1981 mercruiser 120 153 cid

You have at least two problems not related, just my opinion.

Too rich a condition, especially with raw fuel coming out of your cylinder, has to be a carb that is overflowing or leaking badly. The carb probably just ran out of gas or whatever condition made it overflow went away while you were setting the valve lash.

The valves may need to have their lash set correctly now. Usually an engine will start ok if the vavles are close to correct, but will lose rpm if they are too tight, and will be very noisy if too loose.

 

[JustJason]

Re: 1981 mercruiser 120 153 cid

but will lose rpm if they are too tight

Unless they are so tight they do not close and you have no compression. No compression ='s no combustion. No combustion means a whole lot of fuel sittin pretty on top of that piston.

 

[jayandzach018]

Re: 1981 mercruiser 120 153 cid

ok all the valves are set now why is it still hard to start everything is new even the card and its not even a rebuild? is there a video on how to change a shift cable?

 

[JustJason]

Re: 1981 mercruiser 120 153 cid

what are your actual compression numbers at?

I service the billerica area, PM me if your interested.

 

[jayandzach018]

Re: 1981 mercruiser 120 153 cid

ok now i put in a new intake new water pump and lower pump and it is still over heating and how to do install the shift cable?

 

[JustJason]

Re: 1981 mercruiser 120 153 cid

who cares about how it shifts if your having an overheating problem... slow down, step back, and grab the service manual in the "adults only" section. Read everything you can about the cooling system forwards and backwards.

 

[jayandzach018]

Re: 1981 mercruiser 120 153 cid

yes i have a copy of it but i have everything just like the book says, can the valves overheat the motor cuz i adjusting the lash?

 

[Master of the Boat]

Re: 1981 mercruiser 120 153 cid

New impeller in the outdrive. Run it, still overheats ? If yes then:
New t-stat. I would have put a new one in anyway. Run it still overheats? If yes.
Pull off the riser, check to see if all plugged up with rust, and while off, see if the flapper / shutter is broke off and clogging the exhaust.

Hard to start condition, have you cleaned all the connections, the ground also.
The ground at the block if you follow the neg, cable take it off the block and make it shiny clean the cable and the block and bolt where it connects to the cable.
Cable is good at the battery both of them? All connections at the starter, remove the cables at the battery, clean the grounds, the starter connections, and re-install all clean and shiny. Dizzy cap clean, and new points and condenser ?

Fuel system clean? All the filters clean ? The one in the fuel pump, and the fitting that enters the carb, the fuel pickup, and vent checked?
Fuel pump giving you between 4-6 psi.

A good days work i posted above after everything is done and checked and or replaced, run it see if it starts better, and let us know how you made out.

 

[JustJason]

Re: 1981 mercruiser 120 153 cid

can the valves overheat the motor cuz i adjusting the lash?

No they can not.

 

[Master of the Boat]

Re: 1981 mercruiser 120 153 cid

At the top of the forum click on " Adults only " then click on how to start a carbed motor. After you have read that, click on the manual section and d/l your manual free courtesy of Don s. there is a mountain of info there.

Good luck.

 

[jayandzach018]

Re: 1981 mercruiser 120 153 cid

i have a 1981 renken so how do i know what year my engine is?

 

[APPALOOSA2]

Re: 1981 mercruiser 120 153 cid

If the boat is a 1981 and you think the engine is original its probaly a 1981.
You could get the serial number off the engine block and and check it.

How come you ask questions but don't supply all the information that is needed to help you ?

You skip from one problem to the the next without saying if you fixed the original problem.

Their is a whole bunch of good information and knowledge on this forum but you need to ask and answer the questions.

 

[jayandzach018]

Re: 1981 mercruiser 120 153 cid

sorry that post was for the overheating problem so i wanted to know the yea so i can get pats

 

[JustJason]

Re: 1981 mercruiser 120 153 cid

you must be from boston........ the paaaaaaats

 

[jayandzach018]

Re: 1981 mercruiser 120 153 cid

thanks guys all my probleams are fixed now a new one well i bought a new shift cable and i can not know if the cable is adjusted right, there is like two lines comming from the trim pump to a valve and when u push the valve the outdrive will get in gear?

 

[Don S]

Re: 1981 mercruiser 120 153 cid

You would be a LOT better off to start a new thread with your new question. After this reply of mine, 90% of the people will never see your new question, because they don't read every post in the thread. Especially after they get this long.