87 mercruiser 350 rattle/ticking noise

[mattg1024]

Boats been running good all year. 87 mercruiser 350 alpha 1 outdrive.
Ocean was glass smooth today so i opened her up a bit to around 4-4200 rpm. Starting hearing a knocking or ticking type noise from the engine bay. Slow down and it goes away. Sounds like a wrench rattling around in the bilge. got it home and running it with the muffs almost sounds like its coming from the risers? But it was very faint, not the same noise. I'm an auto tech but just getting started with boats this year and was hoping for some help. Done alot of reading around but not much help. Did notice the belts were a little loose but not sure if that could cause my noise. Thanks for any help.

 

[Bondo]

Re: 87 mercruiser 350 rattle/ticking noise

Starting hearing a knocking or ticking type noise from the engine bay. Slow down and it goes away.

Ayuh,... It's Detonating,.... Check the fuel filters,...Goin' Lean will cause it...

 

[mattg1024]

Re: 87 mercruiser 350 rattle/ticking noise

I did shut it off after I heard the noise and it continued to run for a few seconds like it was "dieseling." Not sure if that helps in the diag. It does run on leaded gas, maybe not enough lead additive?

 

[Rat Capri]

Re: 87 mercruiser 350 rattle/ticking noise

why are you runnin leaded gas ?

 

[mattg1024]

Re: 87 mercruiser 350 rattle/ticking noise

lllll

 

[jtybt]

Re: 87 mercruiser 350 rattle/ticking noise

...or build-up of carbon.

How much advance are you running?

 

[mattg1024]

Re: 87 mercruiser 350 rattle/ticking noise

I was told by my wifes uncle (who we got the boat from) that you had too in this motor so the valves would seat properly and it would also prevent pinging. Sounds like I should not be using it? I'm going to put new fuel filter on it and make sure the jets in the carb are not clogged. Also if I just run unleaded it 87 ok ot should I use higher? Thanks...

 

[erikgreen]

Re: 87 mercruiser 350 rattle/ticking noise

Despite what the old owner said, it'll run fine in 87 octane with no lead additive.

To stop the pinging, check your ignition settings, including advance.

 

[jtybt]

Re: 87 mercruiser 350 rattle/ticking noise

Shouldn't need leaded gas in an '87.

What's your WOT? Too much load can add to a detonation problem as well as a lean condition and too much advance. Usually opening the secondaries will allow enuff cool fuel/air to lower the combustion chamber and stop the detonation.

Detonation in a marine engine will kill an engine faster than an auto because of the higher load at all throttle openings.

 

[snoski]

Re: 87 mercruiser 350 rattle/ticking noise

Where do you find leaded gas these days????

 

[mattg1024]

Re: 87 mercruiser 350 rattle/ticking noise

I've been adding lead substitute. Guess I can save some money now.

 

[Bondo]

Re: 87 mercruiser 350 rattle/ticking noise

I'm going to put new fuel filter on it and make sure the jets in the carb are not clogged.

Ayuh,... Why don't you do a Full Tune Up,+ Service while you're at it....
Who knows how long ago Uncle got around to it...

 

[Rat Capri]

Re: 87 mercruiser 350 rattle/ticking noise

I've been adding lead substitute. Guess I can save some money now.

good, you're gonna need it to have those heads rebuilt

 

[Bondo]

Re: 87 mercruiser 350 rattle/ticking noise

Quote:
Originally Posted by mattg1024
I've been adding lead substitute. Guess I can save some money now.
--------------------------------------------------------------------------

good, you're gonna need it to have those heads rebuilt

Ayuh,.... What are you inferring,..??..??

SBC's had hardened seats by 87,...'ell,by 77....

 

[mattg1024]

Re: 87 mercruiser 350 rattle/ticking noise

hmmm so I think I might have found my issue. If your facing the motor theres a lever that attaches to a coil of metal on the left side of the carb that is no longer attached to the intake. Got my book out but cant seem to find what it is. I blame my age for lack of knowlegde. I wasnt brought up in the carb. days...

 

[Bondo]

Re: 87 mercruiser 350 rattle/ticking noise

hmmm so I think I might have found my issue.

Ayuh,... That's part of the Choke,... It's a Problem, but Not the 1 you're lookin' for...

 

[mattg1024]

Re: 87 mercruiser 350 rattle/ticking noise

Darn. I didnt get to the parts store after work so I didnt take off the filters yet. I have a bad feeling about this whole situation but i suppose its a good time/way to learn.

So whats the deal with the lead in gas? Did the lead ruin my heads or what? I'm a bit confused about what Rat Capri stated?

 

[mkast]

Re: 87 mercruiser 350 rattle/ticking noise

What RPM does the engine idle at at operating temperature?

 

[mattg1024]

Re: 87 mercruiser 350 rattle/ticking noise

I want to say around 3-500.

 

[mkast]

Re: 87 mercruiser 350 rattle/ticking noise

good, you're gonna need it to have those heads rebuilt

Not because of the additive.
You might explain your statement.