Mercruiser 3.0 No Spark issues

[Bondo]

Should I add a filter into the pickup or just be diligent in checking the filter on the pump and the in-line filter before the carb?

Ayuh,..... What's Best, is to add a canister type water sep. filter, between the tank, 'n fuel pump,.....
No filter in the tank's dip tube, 'n no in-line filter, anywhere,......

 

[aidanmurphy]

Was able to get out with my digital timing light to check advance. I have base timing set at 1BTDC according to this timing tab. At 2600 RPM with my timing gun set to 23 degrees, the timing mark was showing around 8BTDC . When I turned my timing gun to 28 degrees , the timing mark was about on the 1BTDC mark. Does this mean it is over advancing? The manual states I should be around 23 degrees total advance at 2400-2800 RPM

 

[aidanmurphy]

A few plug pics after a high throttle / WOT run. I still hear some chatter / rattle at higher RPMs. Not sure if it really is knock or not

 

[alldodge]

Don't see a 1 BTDC mark but would agree your about 23 degrees advance

Need more time on the plugs to determine if its actually lean. Correct if I'm wrong but the plugs have very few hours on them

 

[aidanmurphy]

Don't see a 1 BTDC mark but would agree your about 23 degrees advance

Need more time on the plugs to determine if its actually lean. Correct if I'm wrong but the plugs have very few hours on them

Okay, so timing is good. And yes the plugs have about an hour or two total on them. They're practically brand new. Think it's safe to just run the boat for a bit now? I will add that on the first acceleration of the day out of no wake, it will bog under immediate throttle. If you ease into throttle it's fine, and after that punching the throttle doesn't cause any bog.

Edit: I can't visibily see the marks on my timing tab eve after some sanding. I just found the diagram in the manual that looks closest to my tab (same # of points and valleys) and went based off that

 

[alldodge]

I would suggest making the carb run richer. Increase jet size or get a larger carb. A motor won't be destroyed if it runs rich and can be leaned out later

A take off bog can be lack of fuel

Don't run it hard, maybe keep it just enough to cruse and give it time and recheck plugs

 

[achris]

Edit: I can't visibily see the marks on my timing tab eve after some sanding. I just found the diagram in the manual that looks closest to my tab (same # of points and valleys) and went based off that

You need to use a piston stop and verify that the TDC mark you are using is actually TDC.

Chris...

 

[aidanmurphy]

I would suggest making the carb run richer. Increase jet size or get a larger carb. A motor won't be destroyed if it runs rich and can be leaned out later

A take off bog can be lack of fuel

Don't run it hard, maybe keep it just enough to cruse and give it time and recheck plugs

The PO stated that he replaced the carb so it's possible the jetting isn't to spec. How much would you jet up?

 

[aidanmurphy]

You need to use a piston stop and verify that the TDC mark you are using is actually TDC.

Chris...

Thanks Chris will look into getting one

 

[alldodge]

The PO stated that he replaced the carb so it's possible the jetting isn't to spec. How much would you jet up?

Not a carb expert but what I would do is find out what jets are in it now. Then can compare with what should be there, and then can decide what to change

 

[aidanmurphy]

Not a carb expert but what I would do is find out what jets are in it now. Then can compare with what should be there, and then can decide what to change

Will do

 

[achris]

There'll numbers on the side of the carb. Post those and we can tell you what jets should be in it.

Chris.....

 

[1960 Starflite]

I don't have any input, But this is really good thread

 

[aidanmurphy]

There'll numbers on the side of the carb. Post those and we can tell you what jets should be in it.

Chris.....

Thanks Chris I'll have a look tomorrow and update

 

[aidanmurphy]

Just for kicks here is a video of the motor running without the cover to hear it better. I can hear a bit of racket when I throttle up, mostly noticeable in the last couple seconds of video. I might be overthinking the sound but hard to tell what it is

New video by Aidan Murphy

photos.app.goo.gl

 

[dubs283]

I might be overthinking the sound but hard to tell what it is

Possible overthinking it, sounds to like it's an inconsistent rattle, not a rhythmic knock/noise I would associate with pinging/detonation. But I'm not in the boat with you...one test is to have a helper drive while you use a stethoscope to isolate the noise

The plugs look good in the latest pics, appear to have a good color with even burn across the porcelain and tang

 

[alldodge]

I'm not hearing anything of concern, but recorded sounds may not be that good

 

[aidanmurphy]

I'm not hearing anything of concern, but recorded sounds may not be that good

As dubs mentioned it is a more inconsistent rattle vs a knock or pinging sound. The BB in a tin can noise is no longer present that I described when originally starting the thread, whether that is due to higher octane fuel or getting my timing sorted out I'm not sure. Anyways, I will continue to cruise in the boat and put some more hours on the plugs. Will report back with carb details. Going to tackle the bellows install in the next day or two and see if that fixes my leak.

 

[aidanmurphy]

One other thing I "changed" is that when I was checking the fuel pickup, the tube was screwed into the tank only hand tight. When I put it back in I tightened it a bit more snugly. Is this a potential area for an air leak into the line and should I use some sealant on the treads?

 

[alldodge]

One other thing I "changed" is that when I was checking the fuel pickup, the tube was screwed into the tank only hand tight. When I put it back in I tightened it a bit more snugly. Is this a potential area for an air leak into the line and should I use some sealant on the treads?

Should be a non-issue. The tube is just an extension of the fuel line. Being loose around the outside is no issue so long as the tube is not leaking on the inside. If it was leaking then it would run out of gas