2007 3.0 Rattling/Timing

[bjarnold1]

I have a 2007 MerCruiser 3.0 with very low hours. I had the boat out for the first time and noticed under hard acceleration a top-end knocking sound. I immediately backed off the throttle and at cruising speed it is not noticeable. Running on muffs it's not noticeable either-only when under a load. I put a new cap on it, rotor, plugs and wires using AC plugs and the rest factory Quicksilver parts. That didn't fix it so I checked the timing by doing the following procedure :

1. Disconnect the two wires for the shift interrupt switch and plug them together
2. Connect a jumper wire between the two wires with female connectors off distributor

After doing this and checking the timing the mark wasn't even close to the tab on the engine. I had to rotate the distributor a little over 1/4 turn to get it to register on the tab. Does this sound correct?. Would the engine even run if it was that far off?

 

[dubs283]

I had to rotate the distributor a little over 1/4 turn to get it to register on the tab. Does this sound correct?. Would the engine even run if it was that far off?

Are you checking timing at idle on cylinder #1? Is the firing order correct?

 

[bjarnold1]

That is with the engine idling and on the number #1 cylinder. I checked the firing order and the wires are 1-3-4-2. I thought maybe the firing order was off by one at first but the engine wouldn't start and backfired thru the carb

 

[dubs283]

By the sounds of it the timing was too far advanced and there was detonation occurring at higher rpm. The process you describe for setting base timing is correct for the electronic ignition. Does the engine tag specify a timing spec and what did you set timing to?

 

[itsathepete]

Which direction was the timing mark off? To the left or right of the indicator if you are looking at the front of the engine

 

[itsathepete]

One quarter turn equals 90 degrees on the distributor. Did you really turn it that much? That equates to 180 degrees on the crankshaft. I would double check your top dead center on cylinder number one and then find if that lines up with your timing mark. If not make a mark on the balancer to line up with the timing mark.

 

[bjarnold1]

The timing was so far off I didn't see the mark on the pulley until I started rotating the distributor. Could the distributor be off a tooth?. The only thing I hadn't done yet was new spark plugs. The factory manual calls for .045 gap and the old ones were .032

 

[itsathepete]

Distributor orientation doesn't matter as long as it is seated and plug wires located to set timing properly. Recheck top dead center on number 1 cylinder. Verify it with a piece of wire in the spark plug hole or a screwdriver. Your balancer may be off or spun. Then set timing

 

[dave8311]

Might have jumped a tooth or two on the timing chain/belt.

 

[Rick Stephens]

Might have jumped a tooth or two on the timing chain/belt.

Doesn't have one.

 

[dave8311]

Ok, on the gear then?

Or, someone didn't time it correctly to begin with.

 

[dubs283]

Ok, on the gear then?

It has a fiber cam gear, it would strip out before it jumped a tooth

OP: you have changed/set the timing. Does the engine still run okay without the associated noise mentioned earlier?

 

[bjarnold1]

It has a fiber cam gear, it would strip out before it jumped a tooth

OP: you have changed/set the timing. Does the engine still run okay without the associated noise mentioned earlier?

I have not had a chance to take it out on the water yet after adjusting the timing and replacing the plugs

 

[bjarnold1]

Here's the plugs I took out

 

[dubs283]

Kinda crummy pic but plugs look wet. Again, can't see much much but for new plugs they look a bit rich

Guess is carb is adjusted rich for decent idle but running lean at higher rpm. I'd look into fuel delivery, i.e. fuel pump pressure and vacuum. Have you inspected contents/replaced fuel filters?

 

[bjarnold1]

Kinda crummy pic but plugs look wet. Again, can't see much much but for new plugs they look a bit rich

Guess is carb is adjusted rich for decent idle but running lean at higher rpm. I'd look into fuel delivery, i.e. fuel pump pressure and vacuum. Have you inspected contents/replaced fuel filters?

I have not checked the fuel filters. It has almost a full tank of fuel that is at least a year old. I was waiting until I use that up then refill with high octane non ethanol gas and replace the filters at that time

 

[dubs283]

I have not checked the fuel filters. It has almost a full tank of fuel that is at least a year old.

Cool

Check/replace your filter(s). Do your fuel expenditure program and keep up with routine maintenance.

If still running poor investigate further

 

[Rick Stephens]

A couple thoughts here. If the engine is pinging, that is a quick way to burn a hole in a piston. Boat motors run at full torque output 100% of the time, only dependent on throttle setting for how much torque. Like running a car uphill only, and with only one gear. If you hear pinging you are doing damage.

A tank of older gas is not worth the price of a rebuild on your engine. Problem with ethanol fuel is it is hydroscopic. As it sits it grabs free water molecules from the air. Ethanol and water actively attract and combine by making hydrogen bonds. Once combined with water the ethanol drops out of solution with the gasoline and because it is now heavier than gas, drops to the bottom of the tank. This is inevitable with aged gas containing ethanols unless the gas is stored sealed from all atmospheric contamination.

Ethanol's one saving grace as a fuel is it adds octanes to fuel, over 15%, sometimes 20% of the total octane source in the fuel. That's its weakness as well, since as it mixes with water and drops out of solution with the gasoline, it takes the added octanes with it. Your gasoline quickly becomes less than your 9:1 compression motor can safely burn without detonation.

You can either pump the fuel out, or maybe add an octane booster to it. Or burn it and risk your motor.

 

[bjarnold1]

A couple thoughts here. If the engine is pinging, that is a quick way to burn a hole in a piston. Boat motors run at full torque output 100% of the time, only dependent on throttle setting for how much torque. Like running a car uphill only, and with only one gear. If you hear pinging you are doing damage.

A tank of older gas is not worth the price of a rebuild on your engine. Problem with ethanol fuel is it is hydroscopic. As it sits it grabs free water molecules from the air. Ethanol and water actively attract and combine by making hydrogen bonds. Once combined with water the ethanol drops out of solution with the gasoline and because it is now heavier than gas, drops to the bottom of the tank. This is inevitable with aged gas containing ethanols unless the gas is stored sealed from all atmospheric contamination.

Ethanol's one saving grace as a fuel is it adds octanes to fuel, over 15%, sometimes 20% of the total octane source in the fuel. That's its weakness as well, since as it mixes with water and drops out of solution with the gasoline, it takes the added octanes with it. Your gasoline quickly becomes less than your 9:1 compression motor can safely burn without detonation.

You can either pump the fuel out, or maybe add an octane booster to it. Or burn it and risk your motor.

I already put a bottle of octane booster in it before I even fired it up for the season

 

[Rick Stephens]

I already put a bottle of octane booster in it before I even fired it up for the season

If it still pings after timing then the booster might not have been enough. First step is pull and dump the filter, see if there is water in it (personally I'd do that no matter what). If your fuel tank sender is easy to access, might look and see what's on the bottom of your tank. I ended up pulling a tank and doing a high pressure steam out for a customer who had oldish gas in his boat and a non-decent running motor. Had stuff stuck to the inside that was hard to pump out - believe me I tried.