Merc. 3.0l Recent Repower Questions about Rough Idle

[filmmaker101]

I recently repowered my 89 Maxum i/o, 3.0l Mercruiser motor. After getting the motor in, which is 91, I found that this motor has electronic ignition, and there are 2 wires that are not needed for the boat connection on the left insert of the distributor. The motor<br />started up, but seems to idle very poorly. It runs pretty well at higher rpm. I replaced the plugs, cleaned the distributor contacts,<br />wire brushed some of the other contacts, checked distributor wire connection, It has new gas with clean carb.<br /><br />I also have click click click ont he starter when i turn the key. that never happened before so i removed and tested the starter and all is fine there. i did notice that there is a purple/white wire missing, (according to the wiring diagram), from the starter. (the wire that the diagram shows going from the starter to the coil). i dont have an old fashioned coil in this motor, its electronic igition and electronic coil.<br /><br />I also verified that timing is correct.<br /><br />Any clue what could be keeping this motor from running better at idle speed?<br /><br />any and all help would certainly be most appreciated.<br /><br />thank you,<br /><br />dice

 

[tommays]

Re: Merc. 3.0l Recent Repower Questions about Rough Idle

http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=24;t=012808 <br /><br />this don's link will help you with the click on the starter<br /><br />there are a few different ignition systems EST,DDIS,ect so what INFO are you useing to set the timeing ?<br /><br /> http://www.boatfix.com/merc/Servmanl/13/13covr2.pdf <br /><br />this goes over the 3.0 but you have to pick the one for your type of system<br /><br /> http://www.boatfix.com/merc/Servmanl/13/13B4R2.PDF <br /><br />tommays

 

[filmmaker101]

Re: Merc. 3.0l Recent Repower Questions about Rough Idle

i have est on this new motor.

 

[ron7000]

Re: Merc. 3.0l Recent Repower Questions about Rough Idle

tommays: is it possible to get service manual #26 or parts of in pdf like you have above?<br /><br /><br />> Any clue what could be keeping this motor from running better at idle speed?<br /><br />carburetor!<br /><br />... and the fact you only have 4 cylinders. Don't expect too much idle quality below 800 rpms.

 

[rbezdon]

Re: Merc. 3.0l Recent Repower Questions about Rough Idle

Also, make sure the shift interrupt is adjusted and working correctly. I have an OMC so I cant help you exactly but I have read Merc interrupts can be an issue.

 

[tommays]

Re: Merc. 3.0l Recent Repower Questions about Rough Idle

if you follow the manual it will idle fine but you cant take any shortcuts<br /><br />mine will tick away as low as 500 RPM as per my snap on tack<br /><br /><br />it will never be as smooth as a V motor but it wont stall and docks fine <br /><br /><br />tommays

 

[filmmaker101]

Re: Merc. 3.0l Recent Repower Questions about Rough Idle

i finally believed that i had the motor timed, using the instructions posted earlier in this thread and i felt good about the time. i took the boat to the favorite lake and dropped her in and it started great, idled great, i was smiling, the wife was moist.<br /><br />then it happened.<br /><br />i pulled out and gave it some press on the throttle, the motor had no power, the valves started clacking like an irish fest, the smile went away, the moisture dried up and we headed back into the dock. <br /><br />total time on water; 12 minutes!<br /><br />well, after slowly dragging the boat home, i threw the timing light on it again and sure as sun, the timing was in.<br /><br />i threw a wrench at the motor, walked in the house and called my favorite boat mechanic to set up a time to bring her in for the pro's to look it over.<br /><br />the boat now is at the mechanic, im at wits end (as if i had wit before) and i will certainly let you know what happens when i get the call from the boat doctor!<br /><br />thank you for all of your support and comments, they were very helpful.<br /><br />m

 

[Don S]

Re: Merc. 3.0l Recent Repower Questions about Rough Idle

Did you ever put the distributor into base timing to set the timing to spec, (also bypass the shift interrupt), then remove the distributor from base timing for running?<br />If not, then you just had a timing problem from not following the timing instructions.

 

[filmmaker101]

Re: Merc. 3.0l Recent Repower Questions about Rough Idle

hey all,<br /><br />i received one of those crappy phone calls just a few minutes ago.<br /><br />it was the mechanic. he said it was fatal and that she probibly wouldnt make it though the night.<br /><br />i was told that #2 cylinder has 0 compression and suggests either there is a valve problem or a piston ring problem and quoted me a rebuild (at $900.00+)<br /><br />but, as i sat and pondered what kind of service to have for my sweet baby, i realized something important. <br /><br />i just pulled a 3.0l motor from the boat and replaced it with this motor.<br /><br />hint hint nudge nudge, say no more!<br /><br />so it has been decided, i will go and get the boat tomorrow, bring her home for home care, and get ready to perform immediate and imperative surgery myself. i will pull the head and replace with my good head from the other motor and if its a valve problem, that would be the quick fix. <br /><br />i will know more tomorrow, but for now, i must gather and sterilize my tools for tomorrows surgery.<br /><br />i will certainly keep anyone reading this updated.<br /><br />but i can use some support!<br /><br />thanks all,<br /><br />m

 

[whywhyzed]

Re: Merc. 3.0l Recent Repower Questions about Rough Idle

and then throw the old head at the guy who sold you the '91 motor...

 

[filmmaker101]

Re: Merc. 3.0l Recent Repower Questions about Rough Idle

it never fails, if its not one thing its another. the guy was didnt lie, it does run. <br /><br />lol.<br /><br />what a great year of fishin this has been! <br /><br />and the hits just keep on commin!

 

[rbezdon]

Re: Merc. 3.0l Recent Repower Questions about Rough Idle

Unless, the head, piston or what ever was damaged by detonation by not setting the timing as Don said.

 

[filmmaker101]

Re: Merc. 3.0l Recent Repower Questions about Rough Idle

according to the mechanic, he said that this wasnt due to anything i did. i didnt run the motor for an extended period of time, and according to him, this was probibly caused by either the wrong plugs, which came with the motor, and that the 2nd plug was very loose when i got the motor. he said that when a plug isnt deep enough, that can cause the valves to go in that cylinder, but only after quite a period of time.<br /><br />im gonna take my chances and pull the head off and try to see if its either the valves or the piston. <br /><br />im hoping that its the valves, since i have another head ready and waiting. it can be an easy swap if thats the case.<br /><br />wish me luck.

 

[filmmaker101]

Re: Merc. 3.0l Recent Repower Questions about Rough Idle

well,<br /><br />i got her home, ripped the head off and low and behold, it looks as if the head is warped between the second and third cylinder.<br /><br />i will continue with the head swap so we shall see. hopfully i will have it running by tonight.<br /><br />m