how long can i run on muffs?

[brunolund]

how long can i run my boat(96 4.3 merc) on the muffs?
i need to break it in, and it's supposed to be windy as hell tomorrow, and the river still movin' pretty good. was hoping an hour of idle up to maybe 1500. is this okay, or is it only idle on muffs?

 

[DMZ]

Re: how long can i run on muffs?

As most manuals will say it's not a good idea to run over 1500 rpm because the suction could collapse your hose supplying water. As long as this doesn't happen I'm sure you could run it all day with the muffs. Just watch the temp and verify that the water is circulating into and out of the engine.IMHO

 

[SimpleM]

Re: how long can i run on muffs?

If you are going to do this, really, really watch the temps and physically watch the muffs. The muffs tend to "walk" on the lower unit if there is any vibration, and you will be sucking air before you know it. You probably don't want to keep it revved up even to 1500 for that long. Idle mostly and then "burp" the throttle up to about 2K for a few seconds now and then. Sustained no-load running above idle is usually not an optimal situation for any motor; car, boat, lawnmower even for that matter.

 

[J JACKSON]

Re: how long can i run on muffs?

i would wait and get it in the river you really need to brake it in at varying rpms between 1500 and 2500 rpm for 45 minutes that is the way i brake in all racing engines i build if you do it a lower rpms you wont get the splash oiling that is critical to camshaft lift (if its flat tappet)

 

[Bondo]

Re: how long can i run on muffs?

Ayuh,....... You can Run it on Muffs til 'ell Freezes over if you Want,......

But,......
It takes a Load on the motor, to break it in......

 

[bjcsc]

Re: how long can i run on muffs?

Ayuh,....... You can Run it on Muffs til 'ell Freezes over if you Want,......

But,......
It takes a Load on the motor, to break it in......

Exactly...no load = no break-in...

But we understand your anxiety!!

 

[Bondo]

Re: how long can i run on muffs?

Ayuh,.....

And I'll add,...
Doing what you propose is More likely to Glaze the cylinders,+ it'll take Forever to properly break it in.....

 

[John_S]

Re: how long can i run on muffs?

You probably have a roller lifter cam, but if you don't, you do not what to idle it during initial break-in. Follow the recommendations of the engine supplier.

 

[Big Boat Bay Buster]

Re: how long can i run on muffs?

I'm rebuilding a merc 260. I'll do the initial start-up on the muffs. I feel its more controlled conditions and its a good opportunity to check for water/fuel/oil leaks. Since I have a flat tappet cam, I'll run about 1500 RPM for about 15-20 min, then idle for only long enough to set timming and carb settings. Then if all looks good, put it in the water, run it at different speeds for the break-in.
I would suggest something similiar for your break-in
Chris

 

[fishrdan]

Re: how long can i run on muffs?

I'm rebuilding a merc 260. I'll do the initial start-up on the muffs. I feel its more controlled conditions and its a good opportunity to check for water/fuel/oil leaks. Since I have a flat tappet cam, I'll run about 1500 RPM for about 15-20 min, then idle for only long enough to set timming and carb settings. Then if all looks good, put it in the water, run it at different speeds for the break-in.
I would suggest something similiar for your break-in
Chris

Is this the preferred way to break in a new engine? Not questioning your method as it's the way I'm going to do it also, but wondering if there's a better way?

 

[RCSConstruction]

Re: how long can i run on muffs?

Is this the preferred way to break in a new engine? Not questioning your method as it's the way I'm going to do it also, but wondering if there's a better way?

Yep.. Textbook.. Although I have always broke in my cams at 1800-2200 rpm's.

 

[Don S]

Re: how long can i run on muffs?

Here is what Mercruiser recommends for their NEW 2008 engines.
Don't forget, they have to warrant the engines and keep their customers happy. They don't want their engines blowing up every sunny weekend during the summer

20‑Hour Break‑In Period
IMPORTANT: The first 20 hours of operation is the engine break‑in period. Correct break‑in
is essential to obtain minimum oil consumption and maximum engine performance. During
this break‑in period, the following rules must be observed:
• Do not operate below 1500 RPM for extended periods of time for the first 10 hours.
Shift into gear as soon as possible after starting and advance the throttle above 1500
rpm if conditions permit safe operation.
• Do not operate at one speed consistently for extended periods.
• Do not exceed 3/4 throttle during the first 10 hours. During the next 10 hours, occasional
operation at full throttle is permissible (5 minutes at a time maximum).
• Avoid full throttle acceleration from idle speed.
• Do not operate at full throttle until the engine reaches normal operating temperature.
• Frequently check engine oil level. Add oil as needed. It is normal for oil consumption
to be high during the break‑in period.


Here is from a 1995 owners manual

20-HOUR BREAK-IN PERIOD
IMPORTANT: The first 20 hours of operation is the engine
break-in period. Correct break-in is essential to obtain minimum
oil consumption and maximum engine performance. During
this break-in period, the following rules must be observed:
• Do not operate below 1500 RPM for extended periods of time for
first 10 hours. Shift into gear as soon as possible after starting and
advance throttle above 1500 RPM if conditions permit safe operation.
• Do not operate at one speed consistently for extended periods.
• Do not exceed 3/4 throttle during first 10 hours. During next 10
hours, occasional operation at full throttle is permissible (5 minutes
at a time maximum).
• Avoid full throttle acceleration from IDLE speed.
• Do not operate at full throttle until engine reaches normal operating
temperature.
• Frequently check crankcase oil level. Add oil if needed. It is normal
for oil consumption to be high during break-in period.

 

[soler]

Re: how long can i run on muffs?

here is one way.
http://www.ntnoa.org/enginebreakin.htm

here is another, and the way I break in all my motors, bar none:
http://www.mototuneusa.com/break_in_secrets.htm

So, if it were me, I'd put in on the hose to see if all is well, run it up to normal operating temp and check for leaks or other problems. You can probably do some minor tuning here. 10 to 20 minutes tops. Shut it down and let it cool. Now you need to go to the lake and run it like you stole it. It has to be under load, so doing it in the driveway with the hose is NOT an option. After your run, bring it home, change the oil and filter, done!

After it's broken in you can run it all day long on the hose with no damage so long as you ENSURE you have that constant water supply to the engine. I am new to this site, but not new to 4 stroke engines. This is what I do, and have lots of miles on lots of toys!

Good luck!

SOLER

 

[wca_tim]

Re: how long can i run on muffs?

The marine builder that built my 383 told me the following (in a nutshell)

After everything's connected and double checked, fill it with Rotella T 15-30 oil, prime the oil pump / system with tool on drill, then start it on muffs, get the timing close but don't idle any longer than have to. Then run 1500 - 2500 rpms for 15 or 20 min, continually varying rpms during that time (cam break in). Dump / change the oil, refill with Rotella get the timing dead on and check everything over good again, put it in the water and see what it'll do... vary rpm's as much as possible for the first 10 hours and go to good synthetic oil (good anti-scuff additive package) after that...

He said if the engine was built with proper tolerances and components for marine performance applications, the cam was the only thing that really needed to be broken in...

I'll let you know if it doesn't work out once I fire it up...