Ready to sink this damn thing

B

Badfish888

New Member
Jul 18, 2015
85
Va beach
Boat Info
175
Engines
3.0
So last year i had a butt load of issues
between last year and this winter on the engine i have done
plugs,wires, cap, rotor, coil, fuel pump, all new fuel filters, rebuilt the carb with new jets. New timing gear cover, new belts, new trim pump. I have messed with the timing if i advance it anymore it dies If i retard it any more it runs like crap.
So today When i fired it up today The whole boat shakes violently like its running on one cylinder after about 2-3 min it smoothes up and idles at about 850. Put in gear Idles up river for about 1/2 mile, No issues 43psi oil, 140 temp. When i come up off idle it taps Like crazy untill it planes off and i back off the throttle. Runs smooth Any thing over 3800 Taps like crazy. Not pinging Sounds like valve tap. So on the way back i hit a wake and it felt like some one kinked my fuel line. I had to pump the hell out of it to get back home Would not run, or idle. Got back to ramp. Trippled up lines On dock And ran it up to 1/2 throttle. Tapping like crazy And fuel is dribbleing from venturiesand it runs like crap. Only now it will idle. Brought it home and put it on muffs. Idled fine. WTF is wrong with this POS
 
I'm guessing I don't know the year of motor but have you checked the timing advance in the distributor. Some times they get rusty and stick.If newer timing module.
 
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Why are you screwing around with this POS. Freshen up brother, bigger and better things await
 
anti-syphon valve, fuel tank vent clogged, firing order is 1,3,4,2 at idle ,you should not see any dribbling at idle speed. float level could be wrong or the needle and seat are leaking.
 
scoflaw said:
Why are you screwing around with this POS. Freshen up brother, bigger and better things await
Click to expand...
Because until my truck is paid off, this pos is all I can afford, And if I can't even get it running I'll never sell it.
Now. I know I have to go through the whole fuel system but why is it tapping like crazy under load
 
If you are seeing raw fuel that oil needs to be changed.
If a vacuum leak was not detected and timing and carb. calibration changed to mask the real issue these symptoms (except for the tapping) would be apparent. Might also look to something plugging up the exhaust system.
Another area that will cause the tapping, bad idle and high speed rough operation is ignition. A weak ignition will drag a motor's power down greatly. Not completely sure about your boat but Mercrusers had an ignition interrupt switch so shifting was smoother. It's a switch integrated into the shift/throttle assembly that when you slide the gear shift into forward or reverse it causes the ignition to misfire and lower the engine's RPM's. If this switch is acting up it could be the source of the problems.
Another area is if the camshaft went flat you would see missing, no power, and noise. Pull the oil filter and cut it open; look for metallic particles in the filter pleats.
Just some thoughts...
 
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Dripping fuel could indicate its time to rebuild the carb. I had that same issue on a 5.7 and it would not idle smooth, stumbled, lacked power. I had the carb rebuilt and problems solved. Also I agree with the change the oil comment, its likely diluted with gas if you are seeing dripping fuel.
Has this boat run OK for you in the past? If so, I'd doubt that there is anything major internal like a cam going out. Usually its the simple things that can cause a lot of problems.
A friend had that interrupt switch stick on him and he lost half a season replacing other parts. I was down one day looking at it and just disconnected it while the engine was running and it smoothed right out. Its worth a look.
As a great mechanic (my grandfather) told me, start from the simple and work to the complex.
 
And be careful about writing about sinking her in an online forum! If something did happen that caused your boat to sink and you put in a claim, you never know to what lengths they may investigate...
 
Aside from a horrible idle it ran great last year Cruised @ 4k With 6 people all summer long With no sounds. After i put in a new fuel pump It idles and ran great. The first trip if the year it sounds like a tap dancer in my engine compartment. Ive heard rod bearings go out This is to high pitched for that. It rattled when i bought he boat And i did a valve adjustment And it fixed it But this souds kike every valve is loose When i checked the lash yesterday they were all still good
 
Tappets will be at a lower frequency than a rod bearing for sure; the cam turns half the rpm of the crank. Suggest also looking at the output drive train and gimbal brg.
 
How can i check timing advance, Were exactly is it located. I had an idea to rie off to a dock Run it underload until it taps And then try to manualy advance the timing to see if that makes the sound go away. I do t think its the cam. I have zero loss in power
 
Why not have a professional, reputable marine mechanic take a look at your boat?
 
I have been a large diesel marine mechanic for 11 years, Plus out boards. I refuse to take my boat to te dealer who charges $260 for an oul change on an engine that holds 4 quarts and a filter. And opy $160 an hour. I am simply asking people who have most likely known common problems of a 4cl mercruiser. If need be I can rebuild from the crank up. I was just lookig for imput. It is most deff something with the valve train as adjusting lash makes a difference. And ive heard that the hydro lifters go out on these. So i think that will be my next step.
 
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