Engine Rattle, higher RPM's!

[rbh]

Re: Engine Rattle, higher RPM's!

So, lets see if I got this right.
High octane, faster burn, lower BTUs
low octane, slower burn, higher BTUs
rob

 

[bruceb58]

Re: Engine Rattle, higher RPM's!

Speaking of octane...

How old is the gas in this tank? problem with ethanol is that these fuels rely on it for getting the octane numbers since it is an oxygenator. As the ethanol evaporated or decomposes, it also reduces the octane rating of the gasoline. Persoanlly, I would get rid of the old gas and put fresh in.

 

[bruceb58]

Re: Engine Rattle, higher RPM's!

So, lets see if I got this right.
High octane, faster burn, lower BTUs
low octane, slower burn, higher BTUs
rob

High octane slower burn...same BTUs
Lower octane faster burn...same Btus

 

[Apollo75]

Re: Engine Rattle, higher RPM's!

Well, you can only crack something so far then it becomes mute.

Ethanol does increase octane --- don't hurt anything but old hoses. Maybe it evaporates quicker than gas --- --- I don't know. I will look that up for my own information.

Years ago a lot of cheap octane boosters were added to fuel --- now with the catalytic converters most of these old additives (lead) for one cannot be used as they will coat the inside honeycomb of the converter and render it useless in one tank of leaded gasoline. So, the fuel is cracked a little further and (yes) other higher cost additives are added, (ethanol) is an additive used to increase the octane rating --- will extend the oil reserves by 10 or 15 percent --- and has raised the price of corn.


Ethanol fuel will hold more moisture without the moisture dropping out as water --- from what I have read --- so I guess that is what I want in a damp environment.

The rest is in the article and there is much more information out there

Now we have cleaner burning fuels which leave less deposits in your engine and extend your spark plug life

Who could ask for more !

OFM

 

[bruceb58]

Re: Engine Rattle, higher RPM's!

Ethanol does hold more water than gasoline but has a nasty side effect where it creates an emulsion when there is too much water. Ethanol is nasty because of this and other things for marine engines.

Ethanol was not added to gasoline to increase its octane...that was just a side effect. Its main purpose was that of an oxygenator. It has been forced upon the gasoline companies to be used to fight emissions. Otherwise, they would not be using it.

 

[Apollo75]

Re: Engine Rattle, higher RPM's!

Come on fellas --- Bubba said don't cut it

The engine rattles at high RPM under high load and stops rattling at lower RPM under lower load --- higher octane will help this even if other factors are in play here.

If you are a Marine mechanic and asked all the right questions when you see these assorted problems (did the research) then give us your professional advice.

1. Where have you been buying your fuel --- marina ? Maybe the fuel has a high concentration of water, tank rust, crud, etc. --- don't buy your fuel there anymore.

Why do we have spark advance --- to start the fuel burning process earlier as the engine rpm's increases so at the time the pistom reaches TDC it produces maximum power.

Higher octane fuels do not explode / detonate as easily as lower octane fuels --- it is a fact --- stay ignorant if you want

To say --- I have been using regular low octane fuel for years with no problem --- has nothing to do with the article --- add something of value to the post.

I have an old Ford 302 that is supposed to make 188-hp new --- do I need high octane fuel --- probably not --- but, one day while I'm out and the engine is running hotter than usual --- I don't want to hear a ping --- I want to do everything I can to increase my engine life.

OFM

 

[cr2k]

Re: Engine Rattle, higher RPM's!

While they are all barking up the timing tree.

I am over here shaking the timing chain tree.

Valves Tap
Rods Knock
timing/lean Pings
That leaves Timing Chain Rattle

I can't say for sure but you need to determine where the sound is coming from.
Take a long screwdriver or hardwood dowel...Place one end on your ear (Remember Never stick Anything smaller than your elbow in your ear).................Bet you tried that... place the other end on the engine and parts of it (idling, and/or at speed. May have to take a driver and do this on the water) BE CAREFUL NOT TO ENGAGE ANY MOVING PARTS.

This will isolate where the sound is coming from. Could even be Alt. or Circ. pump bearings.

Part of what leads me to cam chain is the change in timing. The Distributor is driven by the camshaft. So timing can change relative to the mark.

If you can follow timing at high speed and it wonders, probably cam chain.

 

[cr2k]

Re: Engine Rattle, higher RPM's!

And BTW a Bad side effect of Ethanol that is of consequence to the marine industry and trailer/small boaters in general is the fact that it dissolves aluminum. Aluminum is what of our our gas tanks are made of. It will appear as very very fine aluminum granules, which can gather in fuel filters and carburetor passages.

It does not do this at a fast rate but over 10 years it is noticeable.

 

[bruceb58]

Re: Engine Rattle, higher RPM's!

Higher octane fuels do not explode / detonate as easily as lower octane fuels --- it is a fact --- stay ignorant if you want

I haven't seen anyone dispute you on this fact yet.

 

[bruceb58]

Re: Engine Rattle, higher RPM's!

And BTW a Bad side effect of Ethanol that is of consequence to the marine industry and trailer/small boaters in general is the fact that it dissolves aluminum. Aluminum is what of our our gas tanks are made of. It will appear as very very fine aluminum granules, which can gather in fuel filters and carburetor passages.

It does not do this at a fast rate but over 10 years it is noticeable.

Its the fiberglass tanks that are the problems. The aluminum tank problem with ethanol is a myth.

 

[cr2k]

Re: Engine Rattle, higher RPM's!

Gasoline is not even classified as a combustible; it is a Flammable.

 

[howlnmad]

Re: Engine Rattle, higher RPM's!

While they are all barking up the timing tree.

I am over here shaking the timing chain tree.

Valves Tap
Rods Knock
timing/lean Pings
That leaves Timing Chain Rattle

I can't say for sure but you need to determine where the sound is coming from.
Take a long screwdriver or hardwood dowel...Place one end on your ear (Remember Never stick Anything smaller than your elbow in your ear).................Bet you tried that... place the other end on the engine and parts of it (idling, and/or at speed. May have to take a driver and do this on the water) BE CAREFUL NOT TO ENGAGE ANY MOVING PARTS.

This will isolate where the sound is coming from. Could even be Alt. or Circ. pump bearings.

Part of what leads me to cam chain is the change in timing. The Distributor is driven by the camshaft. So timing can change relative to the mark.

If you can follow timing at high speed and it wonders, probably cam chain.

I would have to agree. This would be a good avenue to go down. I wouldn't rule out the possibility of a lifter or two that may be collapsing causing a high rpm valve rattle. Just my .02 worth.

 

[BAproject]

Re: Engine Rattle, higher RPM's!

I might be way off base here....but here goes.

Have you taken a look at the harmonic balance behind the drive pulley?

If this is out of tune (or the rubber seal between the between the body and outer ring is shot), then the higher the RPMs the more the engine is going to vibrate.

Also check that the mounds are tight.

Just my thoughts...

-BAproject

 

[KewlBird]

Re: Engine Rattle, higher RPM's!

I checked the jar today...and there appears to be NO water in that fuel...... I did stumble up on a possible symptom......While in the driveway on muffs I revved the engine up and when I went WOT from idle, the engine hesitated quite a bit and stumbled (it also popped once)......Obviously I didn't keep it at WOT but for a second while RPM's went up. I have looked into the secondary butterlies and they appear to pump fuel when you punch it.... Could this be related to the rattling? Carb rebuild needed?

And BTW...I haven't checked the compression lately, and I'm pretty sure it's not lifter or pump noise.

 

[bruceb58]

Re: Engine Rattle, higher RPM's!

Have you actually been back at the engine listening while someone else drives the boat?

Sounds like the accelerator pump squirting gas in although they should be squirting into the primaries.

You can run the engine at the high RPM for a few moments on muffs to determine if the rattle is just RPM related...like something loose. The problem is that the engine and driveline is not under load. You can at least dismiss the harmonic balancer mentioned before as a cause.

 

[bruceb58]

Re: Engine Rattle, higher RPM's!

You said in your very first post that you can run for a few minutes at 3/4 throttle and everything is fine and then the rattle happens. Do I understand that correctly?

 

[KewlBird]

Re: Engine Rattle, higher RPM's!

You said in your very first post that you can run for a few minutes at 3/4 throttle and everything is fine and then the rattle happens. Do I understand that correctly?

That was true, it seems to be getting worse now.....Now immediately when under load at 3,400rpms it rattles....Out of water there is no rattling...

 

[bruceb58]

Re: Engine Rattle, higher RPM's!

Have you been at the engine while someone drives the boat to determine where the noise may be coming from?

More questions...what is your oil level at...not too high and not too low? What does your oil pressure run at?

 

[KewlBird]

Re: Engine Rattle, higher RPM's!

Have you been at the engine while someone drives the boat to determine where the noise may be coming from?

More questions...what is your oil level at...not too high and not too low? What does your oil pressure run at?

I haven't had a chance to.....the Oil pressure is 40-65 at higher rpms. Oil level is right on.

OMG! The more I tinker with it the bigger the problem is getting....I put on a new filter and fired it up....I Let it idle for about 15-20 minutes and then the engine stalled....It restarts but stalls out again....as if someone shuts off the key. Revv it up to the point that secondaries open and it stalls out at higher RPMS. I looked in the carb. now and when I open up the secondaries and the flap, it no longer squirts fuel into the secondaries....I can see fuel shooting in from the side when the engine is running with secondaries open, but it's not shooting it out of the two tubes....The carb. is a 4 barrel. Rochester. Argh!

 

[Apollo75]

Re: Engine Rattle, higher RPM's!

WOW --- you may have to take that thing to a Qualified Marine Mechanic

Check the fuel pump pressure and volume --- rule that out !

You could easily have an ignition issue --- check the cap for any moisture --- do all the checks you can think of while you are there.

They can flame me if they want --- I was a carb and electrical / tune-up mechanic for a lot of years ---- this could be anything from a bad ground to an ignition module, etc.

Bubba says ---> was it the tools in your tool box rattling ?

Take a break and laugh a little it won't fix the boat but will put you in a better mood for round 2.

OFM

_______________________________________
"If the boat is not sinking or on fire ---- Relax."