Merc 3.0l performance issues.

[Bob79]

Hello Guys, Long time reader first time poster. I have a Rinker bowrider with a 3.0 lx engine Serial no- L663000, had the boat about a year, done lots of work
first impeller to get rid of an over heating issue, carb rebuild at the same time as it was bogging down some and fuel tank cleaned. Done the universal joint checked the gimbal at same time as it was done just before i bought it, it was ok.

Next up was the water pump ,exhaust manifold and riser.

Now this is where once i got it back from the shop i noticed a big drop in performance was revving up to full throttle but not getting the same performance speed wise. I have now changed the spark plugs still waiting on leads, ive set the valves, and checked the compression all four cylinders getting 122 psi on cold engine
with WOT, yet to do it warm. What is the acceptable pressure for the cylinders cant find it anywhere. Not the best readings but certainly not the worst and all even.
Exhaust noise from rear of boat sounds a lot louder after replacing exhaust. Coincidence??

Any idea in my drop in performance after the last work i had done in the shop?

Doing all my work on my own now.

Any help greatly appreciated.

 

[alldodge]

Howdy

Loosing performance issue. First check settings
Plugs MR43LTS gap .035
Timing 2 ATDC in base timing mode.

The timing issue would be my first guess of what may have happened. Your shop may have set it to 2 BTDC because they didn't read your serial number.

If you don't know how to set timing or how to set motor in base timing mode let us know, we can advise.

As for the exhaust, it could be the exhaust boot was replaced with an exhaust tube. You don't need the tube but some will say it gives you more performance, but it short your motor will not benefit. Some will replace with tube because its easier and cheaper. To see if you have a tube, raise the drive and look at the bottom boot. If its smooth and short, its a tube. If its long and corrugated its a boot

And your compression numbers are fine

 

[Bondo]

Now this is where once i got it back from the shop i noticed a big drop in performance was revving up to full throttle but not getting the same performance speed wise.

Ayuh,.... Welcome Aboard,...... Are you sayin' it rev'ed to 4800 rpms, but the boat was goin' slower,..??

 

[Bob79]

Thanks all dodge, will check spark plugs and gap today hopefully. I have the est ignition i will check it today too. Am i correct in saying the two white wires on distributor need to be looped to check the timing?

Bondo, i should have worded it better the full rev range is down on power barely got it up to WOT.

Thanks for the replies, will check in later im in Spain so im a few hours ahead of you guys.

 

[alldodge]

I have the est ignition i will check it today too. Am i correct in saying the two white wires on distributor need to be looped to check the timing?
.

Yes connect the two together on the distributer after motor is running. Also remove the wires from the interrupter and connect them together.

 

[alldodge]

ttt

 

[Bob79]

Thats great thank you all dodge, still have not got my hands on a timing light tomorrow hopefully. Spent a couple of hours today replacing the valve cover gasket as it was leaking.

 

[Bob79]

Just an update with this, i checked timing adjusted slightly to 2 ATDC as per instructions above. This was better but not what i was expecting. Today i got a new set of plugs leads and fitted them and i would say that has resolved the issue of under performance.