Hello, Newbe here, Questions 3.0 Mercruiser

[Airgunner7]

Hello, Newbe here...

I have a 2004 maxium 3.0 Mercruiser I/O that I want to get in tip top shape. I have found several answers just going through old posts but, have some more questions to ask.

Is there a good write up on the timing? I'm confused about the interupt that needs to be temp bypassed, I found the white wires to jump....without doing anything it is at 14 deg @ 900rpm and it says it should b @ 1deg


Is 170-180 comp #'s OK?

Has a vibration like something is not quite right even though it drives good and really doesn't like to idle below 800 without a noticable miss. I keep it at 1k

Has New Plugs

Boat came from CA and I am at 3000ft - Can I adjust anything for high altitude?

Thanks for any help.

 

[fishrdan]

Re: Hello, Newbe here, Questions 3.0 Mercruiser

Look in the "Adults Section" sticky at the top of this forum, there should be a manual for your ignition (EST?) and how to time the engine.

1000RPM is too high and your drive isn't going to like it, hard on the gears, going into gear. Keep your RPM at the Mercruisers specs, something like 650-700 RPM while idling in gear.

You said new plugs (which plug #?), but how about cap rotor and wires too?

At 3000' I wouldn't worry about tuning anything on the engine for "altitude", prop maybe if you are not getting the right WOT RPM. I don't mess with my engine until I'm over 5000', that's when the power drop starts to get noticeable. Power loss at elevation is about 3% for every 1000', so you are less than 10% down on power, easily made up with a prop change,,, if needed...

 

[Airgunner7]

Re: Hello, Newbe here, Questions 3.0 Mercruiser

Thanks,

I tried to download the manual and it wanted me to sign up for some membership so I stopped the download...maybe I just need to sign up?


I could not get AC-MR43LTS 's so the parts store gave me autolight 103's


Upon futher inspection it sounds like the noise is near the coupler behind the motor. Maybe I need a gimble bearing? I did turn down the idle and it did not stall at 700 but, the missfire is more noticable and still have the rattle too. Vibration is also noticable throughout all rpms/gears.

How hard is it to remove outdrive and replace gimble, u- joints and impeller all at same time?

Must have several things going on.

 

[Airgunner7]

Re: Hello, Newbe here, Questions 3.0 Mercruiser

Oh, the timing light flashes steady and smooth and compression number apears good so maybe adjust the valves?

 

[fishrdan]

Re: Hello, Newbe here, Questions 3.0 Mercruiser

2004 boat should have the bellows replaced if not done so all ready, if they go bad the gimble bearing and Ujoints are suspect for your noise behind the engine. Bellows, gimble bearing, Ujoints are not that bad if you are mechanically inclined, but a PITA the first time. You will need some special tools, bellows expander, engine alignment tool, etc...

The manuals in the adult section are downloadable, just wait for the download site to go through it's timer, you have to wait 60 seconds (or something like that) before downloading if you are not signed up. I didn't sign up...

BTW, when I said idle at 650-700RPM while in gear, this is while the boat is in the water. You can't adjust it correctly on land. I set mine for 750RPM on land and it fell into spec when I checked in on the water, but you still need to check/adjust it on the water.

Not sure if you are aware of this, but most auto parts should not be used on a marine engine. You are probably fine with the plugs (thought I would get the right ones) but don't go swapping out marine parts for auto parts.