Re: Engine sounds like marbels and diesels after stopping
- From: "Nate" <nsaptaemcpcrnonf@xxxxxxxxxxxxxxxx>
- Date: Sat, 27 Aug 2005 17:23:04 GMT
"Bryan" <bryan.459@xxxxxxxxxxxx> wrote in message
news:xw0Qe.1182$dw4.676@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
> "Nate" <nsaptaemcpcrnonf@xxxxxxxxxxxxxxxx> wrote in message
> news:wT_Pe.1168$dw4.1009@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>>
>> "Bryan" <bryan.459@xxxxxxxxxxxx> wrote in message
>> news:lLRPe.257$sP7.220@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>>>I just had my 20 hour service on my new motor. I'm no mechanic, so I had
>>>it done by the Sea Ray dealer. I mentioned to them that it had a
>>>difficult first start once. Also it has been continuing to run
>>>("dieseling") after turning off the ignition. They said everything
>>>checked out, but they went ahead and "advanced the timing a little."
>>>
>>> Could be my imagination, the boat seems to run well, but it sure doesn't
>>> seem to sound like it did before the 20 hour service. Instead of a nice
>>> tight sounding motor it sounds like it's full of marbles.
>>>
>>> Why the "dieseling" before and after the service?
>>>
>>> Does advancing the timing alter the sound of a motor?
>>>
>>> Sea Ray 185
>>> 6 Cylinder 4.3L Alpha1 Mercruiser
>>>
>> I think I would find another mechanic. I assume this is a brand new
>> motor with 20 hours on it. Why would the mechanic say there is nothing
>> wrong, but let's fix it anyhow? Andvancing the timing to create more
>> compression will lead to pinging with low octane fuels. But that 4.3
>> Alpha is designed to run on low octane fuels.
>>
>> There are a lot of ways to increase the performance on a boat, be it
>> inboard, outboard or I/Os. Most people want to increase out of the hole
>> take offs by increasing power from the motor. But it is more important
>> to maintain the highest available RPMs without exceeding the
>> manufacturer's recommended top RPM. You don't do this by advancing the
>> timing unless the timing is off. You do this usually by changing the
>> prop pitch. The idea is not to get max RPM...but to get as close to the
>> manufacturer's top end as posible without sacrificing performance.
>>
>> I would also change jets on the carb if it were going from a Sea Level
>> condition to say 6000 feet above Sea Level, or vice versa. Then I would
>> match the prop pitch to calm those RPMs back down.
>>
>> Odds are, if they changed the compression, they also changed the max RPM.
>> If they did not also change the pitch of the prop, you really need to be
>> aware of the max RPM rating from the owner's manual. You'll need to be
>> sure you don't over rev the engine. Normally you should be able to open
>> up to WOT and not have to worry about max RPMs. But if they advacned the
>> available RPMs by advancing the timing, now you have to be the governor.
>> Good luck with that.
>>
>> Nate
>>
>
> Thanks Nate. Learning more by the minute. I finally figured out what WOT
> means thanks to your reply! By the end of this thread, that I
> accidentally posted to this group, I'll have a clue. I'll compare my new
> max RPM with my operator's manual top RPM next time out. I wasn't trying
> to increase anything! I just mentioned to the dealer, when they asked how
> it was running, that I experienced a dieseling event a couple of times and
> a hard start one morning. Instead of sticking with "everything is as it
> should be, let us know if it continues" they decided to fiddle with it. I
> should have kept my mouth shut!
>
I get a dieseling effect on my 4.3 Bravo usually on the first trip of the
year. The gas has been sitting in the tank all winter. Once I run that
tank dry and re-fill it the deisel effect goes away. I suppose I could run
some additive, but I usually don't think of it until I launch the boat, cruz
across the lake and then kill the engine. My solution is to run the tank
dry by cruzing WOT (there it is again..lOL) until the tank is near empty,
then I find a fuel dock. It's more fun that way.
A higher octane fuel may solve your original problem. It sounds like the
timing adjustment may have worsened it. I would think retarding the timing
would help more than advancing it. If the cylinders have any carbon build
up on the top, the carbon will heat up and glow like a glow plug. If you
get enough compression, the carbon will glow hot enough to ignite the fuel
before the spark from the ignition system. Advancing the timinmg will make
that worse, not better.
However...if you recently moved the boat to a higher altitude, advancing the
timing may help since the air is not as compressed at higher altitudes,
advancing the timing makes up for this somewhat leaner air.
Again...how old is this engine? I assumed new, but I'm thinking that may
not be a good assumption.
Nate
.
- Follow-Ups:
- References:
- Prev by Date: Re: Nova Scotia results
- Next by Date: Re: O.T. Wal-Mart: another shooting and stabbing at Wal-Mart in Alb...
- Previous by thread: Re: Engine sounds like marbels and diesels after stopping
- Next by thread: Re: Engine sounds like marbels and diesels after stopping
- Index(es):
Relevant Pages
|
