Mercruiser 165 Inline 6 timing/carb adjustment?

[auscarter12]

I have an early 70's model (74 I believe according to the serial number).

I noticed the other day that the bolt and bracket holding the distributor down were both loose and the distributor moved freely - therefore the motor is now out of the appropriate timing. I have a Mercruiser Shop Manual that specifies 6 degrees BTDC, but even at 6 degrees I am having trouble starting the motor. To start it, I have to put the motor in gear and open up the throttle (unfortunately I do not have a neutral shift button on my shifter). After starting it and letting the engine warm up, it runs great. Starting is my only issue. Even starting the motor after it is warm is difficult unless I put the boat in gear and open the throttle.

There is no vacuum advance on the distributor.
Spark plugs are new and are gapped according to my manual at .035
Distributor cap and rotor are new and the points are appropriately gapped.
Ignition coil and wires are new.
The carburetor has been recently rebuilt.
I have set the timing to 6 degree BTDC with a timing light.

My question: Is this a timing issue, a carburetor adjustment issue, or a mixture of both? I am afraid to touch the adjustment screws on the carburetor because I know how finicky they can be when out of proper adjustment. Also, I was told by my mechanic to not worry about what the manual says, but to adjust the timing by ear - unfortunately I have little experience with this. Any help on this issue? Thank you!

 

[harleyman1975]

Find a new mechanic! Timing is to be set to spec then everything else is adjusted after that. you could try checking your points dwell with a dwell meter (should be 30 degrees) that will let you know that your points are dead on. Does the carb have an electric choke stat or a "stove pipe"? If electric is there power to the choke stat? Don't adjust the carb mixtures or idle screws until engine is up to temp. Are you sure there is not a neutral or disengage on your telegraph/control lever? on the old ones there is a black knob in the center that pulls out about a 1/4".

 

[HT32BSX115]

I have an early 70's model (74 I believe according to the serial number).

I noticed the other day that the bolt and bracket holding the distributor down were both loose and the distributor moved freely - therefore the motor is now out of the appropriate timing. I have a Mercruiser Shop Manual that specifies 6 degrees BTDC, but even at 6 degrees I am having trouble starting the motor. To start it, I have to put the motor in gear and open up the throttle (unfortunately I do not have a neutral shift button on my shifter). After starting it and letting the engine warm up, it runs great. Starting is my only issue. Even starting the motor after it is warm is difficult unless I put the boat in gear and open the throttle.

There is no vacuum advance on the distributor.
Spark plugs are new and are gapped according to my manual at .035
Distributor cap and rotor are new and the points are appropriately gapped.
Ignition coil and wires are new.
The carburetor has been recently rebuilt.
I have set the timing to 6 degree BTDC with a timing light.

My question: Is this a timing issue, a carburetor adjustment issue, or a mixture of both? I am afraid to touch the adjustment screws on the carburetor because I know how finicky they can be when out of proper adjustment. Also, I was told by my mechanic to not worry about what the manual says, but to adjust the timing by ear - unfortunately I have little experience with this. Any help on this issue? Thank you!

Howdy,

btw, marine distributors usually do not have vacuum advance.

Once you have the timing set properly (assuming the engine is otherwise healthy [compression etc]) you still likely have a carburetor adjustment problem. That engine has an automatic choke that could be maladjusted............and even though the carburetor WAS "rebuilt" it could still be a carburetor "problem".

I would NEVER set the timing by "ear" because you could end up with too much advance. That could result in detonation and catastrophic engine failure. Just follow the service manual instructions. Make sure that if it's an adjustable timing light, it's set right and ensure that the damper hasn't "slipped" (that can cause a wrong timing measurement)

You may need to re-rebuild your carburetor.

There's also nothing wrong with adjusting the idle mixture screws. They're really not all that finicky!

The carburetor must be adjusted with the throttle linkage disconnected. (you don't want the cables applying pressure to the throttle plate in either direction.)

You also need to ensure that the automatic choke is operating properly.

Regards,

Rick

 

[auscarter12]

HT32BSX115

Thank you for your advice! It's possible that with the timing being out of adjustment the carburetor is also out of adjustment for the motor, correct? In previous experiences carburetors have been very finicky so I am usually scared to do anything to one unless I have to. The choke is a thermal choke, but maybe it needs to be adjusted (which I know how to do). I will try a choke adjustment before attempting to play with the idle and air screws on the carburetor. Any other advice?

 

[Scott Danforth]

boat carburetors do not have fast idle cams. when cold, they do need throttle to start (normal). Fuel injection helps this with the IAC and fuel maps.

if your control does not have a button for throttle only, then you pull the handle out toward you. All controls have a throttle only function.

fire your mechanic, he is an idiot.

 

[Bondo]

if your control does not have a button for throttle only, then you pull the handle out toward you. All controls have a throttle only function.

fire your mechanic, he is an idiot.

Ayuh,...... I completely agree with Scott,......

A control without throttle only is broken junk, 'n needs fixin',....

 

[ziggy]

Timing is to be set to spec then everything else is adjusted after that

careful with that statement. i understand it to be the other way around. dwell effects timing. set dwell first, then timing. set timing with 650-700 rpm. the mechanical advance starts to engage pretty darn quick. between 750-1000 rpm best i can read the chart in service manual 2.

if ya got a mercrontol like i got in my '72 and '75 165. there'll be a little black button at the pivot point of the control. push that black button in and move the throttle fwd. to adj. throttle w/o being engaged in fwd.



kinda crummy pic of the throttle, but ya can see the black button.

 

[HT32BSX115]

fire your mechanic, he is an idiot.

Yeah.............I'm agreeing with that!

 

[harleyman1975]

Ziggy I did not make that very complete did I? should have said set points and double check with Dwell meter then set timing to spec...THEN move on to the rest of it! My bad. Sorry if I caused any confusion auscarter 12.

 

[auscarter12]

harleyman1975 ziggy

Thank you guys! Ziggy I also have an Aristocraft like you. My control is an aftermarket one, actually made for an outboard. But it works for the time being. It didn't have the original MerControl like yours when I bought the boat, although I want to install one on it again. My control is a Quicksilver one and it does have a square black button in the center but if I pull on the button, the button just pops off. If I push in on the button it does not engage anything. Maybe my shifter is just busted and needs to be replaced or it needs to be taken apart and lubed up. I do know that if my type of shifter is taken apart it is a PITA to get back together properly and functioning properly.