Can u Solve this Problem???

[lucasier]

Hi guys.. Got an 06 185 sport with the 3.0lt Mercruiser and TKS carby. The problem I have is as follows...

Under WOT or full throttle esp when under load or heats up I hear a pinging or arcing noise from the motor.

To try to remedy this by doing the following.
1. I filled with fresh gas and added a bottle of the ol Nulon Octane booster. ( in case of low octane fuel)
2. Changed the plugs (which were stuffed)
3. Increased the Accelerator Pump on the carby one hole richer.

After riunning fine the next trip out after a few hrs skiing and cruising on the way back to the ramp I noticed the problem returned again.

Is this a common problem...?Any suggestions? Could it be Leads, coil or timing (if timing wouldnt it be there all the time??).

Thanks in advance.....

 

[SCORPIO]

Its called detonation or preignition and is caused by over advanced timing for the octane rating of the fuel you are using. It won't happen all the time because at WOT you are running maximum timing advance. Either increase the octane of the fuel by using premium 93 octane or retard the timing. I think you should put a timing light on the engine and see exactly where its set now and then set it to spec. Don't run it too long like it is now or you risk putting a hole in a piston.

 

[lucasier]

Thanks Scorpio.. I think u hit the nail on the head it definately seems to be a timing issue... however. Being a newby, before i checked the current timing i loosened the distributor which possibly moved a bit before I threw the light on it as timing was showing around 2deg ATDC at idle.

I jumped the two wires on the distributor, disconnected the shift interupt switch and joined the wires from the harness together before I hooked the light up. But could not verify my revs were around 700rpm (would that throw things off if not exact?)

In any case the according to the mercruiser book and my specs on my air filter..regarding timing specs I assume that my timing specs are as follows:

Initial timing is 2 deg ATDC
15 Deg BTDC
26 Deg BTDC at total advance

The timing tab only goes to 12 degrees so I estimated what I thought 15 deg BTDC was and it was pinging again. I had to back it off to around 12 to stop the pinging when giving it a quick rev. So either I have stuffed up somewhere, my timing specs are wrong or there must be another problem. As mentioned on my last trip I increased the accelerator pump richness 1 notch, topped up from 1/4 tank of gas with regular unleaded and threw in a bottle of Nulon Octane booster. Ran fine most of the day. After going through around 1/3 to 1/2 tank of gas is started to ping. Have I done something wrong with the timing?

I was going to just take it out on the water for a test run. If it is lacking power I assume I adjust advance till it pings at WOT and then back off distributor until its okay??? Any thoughts

 

[MaddyDean]

A friend had the same problem on an 06 Bayliner (20-footer) and it was the timing. he found it a year into and took it back to dealer; they adjusted and all was good.

 

[tdappleman]

What do you mean the plugs were stuffed? You may also have some carbon buildup - either an incomplete burn or engine isn't getting up to proper temperature. In addition to checking your timing, I'd also run some top end engine cleaner through it - either Seafoam or something like Amsoil Power Foam.

I wouldn't adjust the timing by feel - depending on which ignition you have on the engine they can have different steps required to accurately set it. For example - on mine I have to ground a wire at the distributor prior to setting it. If I skip this step, the ignition will try to compensate. You will need a good timing light in order to do this properly. Do you know the ignition type?

 

[SCORPIO]

Get a digital timing light with an lcd readout and advance and tach functions. Connect the light and aim it at the timing pointer. Set the advance at 0 and see where the timing mark aligns. Then set it to your max advance and rev up to about 3000 rpm and see if the mark aligns with the 0 on the timing pointer. If it doesn't, either advance or retard the timing on the light to determine what your max advance is. Then determine what you need to do to get the max advance at 3000 rpm within spec.
I don't know what your base timing should be but on my 5.7s its 8BTDC. I'd worry more about what your total advance is than the base timing. I've been told to set the max advance at spec and let the base timing fall where it wants. It still sounds like its over advanced.
BTW be sure to follow any instructions related to putting the engine into timing mode before starting the timing procedure.

 

[Alibuma]

You mentioned that you use the boat for skiing. Did you or the previous owner put a lower pitch prop on the boat to get more "out of the hole" action? What I am driving at is that it could be your rev limiter kicking in if your RPMs at WOT are too high.