3.0L Mercruiser

[penguin356]

I have a '86 3.0 L Mercruiser. The P&D have been replaced by a Pertronix solid state pickup/ignition. I just replaced the carb with a new one.<br /><br />Here is where I need some help. I have the carb tunned in pretty darn close to where it needs to be. The engine is ideling (@temp in the lake) at about 850 RPM and is very smooth. The timming is also darn close. If I drop the throttle wide open, the boat comes out of the water good, but the lifters chatter really bad.<br /><br />I am thinking one of 2 things:<br /><br />1.) Timming is still off<br />2.) Bad gas<br /><br />I am not sure how much gas is still in the tank. I am thinking about adding some Octane Boost. Got any other ideas/suggestions?

 

[Wotknot]

Re: 3.0L Mercruiser

You're headed in the right direction. Could be both. I'd start with fresh high-octane liquid gold and see if that helps......then on to #2 - timing.

 

[jeff13601]

Re: 3.0L Mercruiser

If there is not much gas in the tank it may be better to just drain, and then put in the high octane. You need to be careful with the octane boost

 

[weatherz]

Re: 3.0L Mercruiser

First, check and set your timing with a light. How do you know it is "darn close"? Could also be that u need to rejet or adjust the float on your new carb. A lean condition will cause pinging under load and damage to the pistons. What do your plugs look like? Should be a light brown. If the insulator is white, it is too lean.

 

[penguin356]

Re: 3.0L Mercruiser

The reason I say "darn" close on the timing is this. The engine does not sputter when the throttle is dropped. I have had the boat sputter/shimmy and then "pick up" when the timming was off. I know the factory spec is 8 degrees BTDC. The boat just does not act "happy" at that setting with the solid state iginition system.

 

[weatherz]

Re: 3.0L Mercruiser

U need to check with a timing light that u have no more than 26-28 degrees of total advance (base timing plus centrifugal advance). Sounds to me like it's not your lifters chattering, it's detonation caused by too much advance / incorrect timing. A motor will likely sputter/shimmy if it has retarded timing, however it will accellerate smoothly but detonate if it is too far advanced. Also will run hotter than normal if too far advanced. If U have no timing light try retarding the timing a little at a time and see if the rattle goes away. Hope this helps