Mercruiser Setting Timing on 3.0L

[ESGWheel]

Yes
And to be clear at top dead center on its compression stroke

 

[DanOnTheBoat]

Yes
And to be clear at top dead center on its compression stroke

Makes sense. When Im on the compression stroke both valves will be on the same level? Also what if I didnt rotate the engine at all when it was taken apart, can I just adjust them now? Or its a must to have every cylinder ATDC compression stroke?

Update picture almost there

 

[ESGWheel]

Hopefully it has been clear to you based on my posts that in addition to guidance I also try to instruct. Said differently it is in my nature to teach. Perhaps you have heard the expression: "Give a man a fish, you feed him for a day; teach a man to fish, you feed him for a lifetime"

I know you want to learn so its time you fished. To help with that, I provide this video I found link.

Based on this and other info you have been given or have searched out, I would appreciate if you posted your own answer to your question.

And then I will reply to your answer as in that is correct or otherwise

 

[Bondo]

When Im on the compression stroke both valves will be on the same level? Also what if I didnt rotate the engine at all when it was taken apart, can I just adjust them now? Or its a must to have every cylinder ATDC compression stroke?

Ayuh,.... it doesn't matter whether you rotated the motor, or not,....
Now, you must rotate it to Tdc, compression stroke, on #1 to set the valves on #1,.... Then turn it to Tdc compression stroke, on each of the other cylinders,.....

I don't like the idea of turning the pushrods to find 0 lash, I gently lift 'em up, 'n down to find 0 lash, then tighten 3/4s turn tighter,....

Btw, it's Tdc,...... ATDC is where most motors have the ignition timed too,.....

 

[alldodge]

I don't like the idea of turning the pushrods to find 0 lash, I gently lift 'em up, 'n down to find 0 lash, then tighten 3/4s turn tighter,....

Agree up/down not turn, does not matter if you can turn it then it may be in the right spot but may also be just past it, based on how hard your turning. It can always be turned unless it's too tight already

Because everyone has one, here's mine
I don't bother with TDC other than when setting distributor in to get close to TDC prior to first start and adjustments.

I rotate crank and look for which valves are traveling down (opening valves). The valves that are open means the ones next to them are closed. I just the closed ones, make with grease pencil and rotate some more. Once all marked they are adjusted

 

[DanOnTheBoat]

Hello all my fellow boaters! Excuse my absence, got caught up with school work... Im sure you guys are all wondering if I got the boat to run... or well explode lol. Im happy to announce that its all running! I got it all running and dialed in on Saturday. Worked all day on it but it payed off. Here's a video of it running, this is a cold start without pumping it and no throttle. Last time I started it was on Saturday for the very first time. I started it again since I'm doing an oil change. Id like to thank you everyone once more for all the help and support!

NOTE: I still did not check timing, I'm getting a timing gun tomorrow will get to that. My guess it is still off.

 

[ESGWheel]

Dan,
Congrats on your accomplishment! I was looking over this long thread b/c I recalled there was more do and if you go back to post #4 and 7, you will see there is. That includes routine maintenance items as well as tracking down what looks to be a rich running situation. And recall that while possible the head gasket just let go, its not likely unless something caused it, like an overheat.

My suggestion:

1. Get the timing done, this is an important next step
2. Start a new thread titled something like “New to me boat, what maintenance items should I do?” And you will get a lot of good advice on what needs to be done. Note the lack of routine maintenance could have easily led to the overheat condition, so getting this done is an import step as well.
3. Post the maintenance run the motor on the hose at idle for an extended period (like 30 min, perhaps more) and monitor temps. If anything unusual (hot) shut down and investigate. If all good, get the boat on the water and under load while monitoring temps and if all still good great, else investigate.

 

[kd4pbs]

Glad you've got it figured out, Dan! The bride and I have been "up in the holler" enjoying a much-needed vacation totally disconnected from the world, and it felt great! We're looking forward to hearing about your adventures.

 

[Lou C]

Great work! I did a similar job on my '88 4.3 V6 back in '17. The cleaning and parts inspection are important, as is keeping everything organized. I would consider cleaning the carb, I think with your compression test results as consistent as they are now, it should idle smoother. Also, be careful about setting timing, make sure it's right, these engines are susceptible to detonation and that's one of the main causes of blown head gaskets. I do think yours may have been done before, because I don't think Fel Pro is the OEM on a Mercruiser. Beyond that to avoid another blown HG, make sure your boat is propped correctly, in that it reaches the specified WOT RPM at full throttle. And, despite what Merc says on an engine known for blown head gaskets and detonation, use at least midrange fuel, meaning, 89 octane instead of 87. So, the things to keep in mind to avoid a recurrence:
proper timing
use good fuel, 89 octane or better
engine must be properly propped and reach the specified WOT RPM as per Mercruiser's spec
inspect spark plugs for proper mixture, you don't want the engine running too lean, that also contributes to this problem

 

[DanOnTheBoat]

Dan,
Congrats on your accomplishment! I was looking over this long thread b/c I recalled there was more do and if you go back to post #4 and 7, you will see there is. That includes routine maintenance items as well as tracking down what looks to be a rich running situation. And recall that while possible the head gasket just let go, its not likely unless something caused it, like an overheat.

My suggestion:

1. Get the timing done, this is an important next step
2. Start a new thread titled something like “New to me boat, what maintenance items should I do?” And you will get a lot of good advice on what needs to be done. Note the lack of routine maintenance could have easily led to the overheat condition, so getting this done is an import step as well.
3. Post the maintenance run the motor on the hose at idle for an extended period (like 30 min, perhaps more) and monitor temps. If anything unusual (hot) shut down and investigate. If all good, get the boat on the water and under load while monitoring temps and if all still good great, else investigate.

Thanks for the advice ESG, will do.

 

[DanOnTheBoat]

Great work! I did a similar job on my '88 4.3 V6 back in '17. The cleaning and parts inspection are important, as is keeping everything organized. I would consider cleaning the carb, I think with your compression test results as consistent as they are now, it should idle smoother. Also, be careful about setting timing, make sure it's right, these engines are susceptible to detonation and that's one of the main causes of blown head gaskets. I do think yours may have been done before, because I don't think Fel Pro is the OEM on a Mercruiser. Beyond that to avoid another blown HG, make sure your boat is propped correctly, in that it reaches the specified WOT RPM at full throttle. And, despite what Merc says on an engine known for blown head gaskets and detonation, use at least midrange fuel, meaning, 89 octane instead of 87. So, the things to keep in mind to avoid a recurrence:
proper timing
use good fuel, 89 octane or better
engine must be properly propped and reach the specified WOT RPM as per Mercruiser's spec
inspect spark plugs for proper mixture, you don't want the engine running too lean, that also contributes to this problem

Thanks Lou, I've done the timing on it, set it to 2° ATDC as it said on the carburator air filter(Before doing timing, I checked the mark on the crank wheel and it was WAY back my guess about 25° BTDC at idle...) Ive also set the idle RPM to about +/- 750RPM. I than plugged the wires I bypassed back together and revved it to about 3000-3500RPM and the timing advanced to about a very steady 12° BTDC. From what Ive looked up and researched thats how it should be. Also the carburator looks to be brand new and its OEM so I dont think I have a problem with the carb. After doing the timing it starts like an EFI engine lol.