No Pressure After Oil Change

[achris]

...As for the fuel problem. It will probably just be easier to start and let it idle so it can clear the lines as long as it will idle....

Do not do this on muffs. With no exhaust back pressure, the valve overlap will pull water in from the exhaust into the cylinders. In your owner's handbook it warns against running at idle on muffs, but doesn't say why. This is why.

If you run on muffs, run at around 1200-1400 rpm. If you idle (650rpm), you WILL pull water in...

Chris......

 

[andrewterri]

Since I already ran it when I typed that should I go out and start it dry to make sure I don't have water in the cylinders and just eat the damage to the impeller? I never run on hose since boat is usually on a lift but all the docks were removed to be rebuild before everything was shut down. We are taking the boat to the lake tomorrow lile I said but diffently don't want to leave water in cylinders. I ran it for 30 seconds but sounds like that does not matter. I remembered reading that in manual but though it was an overheating at idle issue

 

[achris]

Don't run it dry. Just put it back on the muffs and run at 1200-1400 for a minute. DO NOT RUN DRY!

 

[alldodge]

In your owner's handbook it warns against running at idle on muffs

Have not seen this, is it just with EC motors?
I have no issue running my 530HP motor on muffs at idle

 

[achris]

Have not seen this, is it just with EC motors?
I have no issue running my 530HP motor on muffs at idle

It's only for Vortec V6s... (post 1996)

I can scan the page if you like.

 

[alldodge]

Would like to understand the issue.

V6 but not V8, and EC motors have more exhaust to go thru

 

[Lou C]

Interesting. I know that Volvo & OMC made 2 changes to the V6 exhaust system when they changed to the Vortec:
1) changed the angle of the exhaust pipe between the elbow and the Y pipe to more of a sharp right angle to make it harder for water to travel back up
2) added a one way vacuum break valve to each exhaust elbow to eliminate vacuum in the exhaust system, these are one way valves that allow air in but not out obviously.

When I updated my old OMC to the later style exhaust I used the later style exhaust pipes but didn’t have to add the check valves because it’s a pre Vortec but if I repowered this boat with a Vortec V6 then I’d have to add the check valves.

 

[harringtondav]

When I was a sprat 45 yrs ago I did remote station service on RR locomotives. RR shut them down overnight to save fuel. Restart process was critical. Each cyl had a test **** that was opened and the engine was bumped over to purge any coolant that may have leaked in. Then tighten the the 16 test cocks and fire it up.....unless the engine was idle > 12 hrs. Then an electric pump with heated engine oil was connected to oil circuit ports and oil was cycled thru for 10 minutes to prevent dry wiping the crank bearings.

Reading this post made me wonder if similar oil system 'pressure priming' could be cobbled on the Merc's remote filter's tubes to bleed and saturate the oil filter.

 

[Lou C]

Hey what's a 'sprat'?
I have heard rare cases of oil pumps losing their prime during an oil change and it makes sense given the extra distance oil has to travel with a remote system that this could happen. I have not added one to my present engine because I can still get to the filter if I take out half of the rear seat (takes about 10 min) but if I had one, I'd want to be able to prime the supply line with oil as noted above.

Getting back to the not running a V6 Vortec engine on the water hose at idle....the pic shows the sharp right angle in the exhaust pipe from the elbow to the Y pipe, the early design had more of a gradual curve...

Late design with check valve:
http://www.volvopentastore.com/Exhau...view_id.776004
check valve is part # 27...one in each elbow...

early design with no check valve and different exhaust pipe....

https://www.crowleymarine.com/johnso...cfm?mdl=FHYBHM

 

[tank1949]

Interesting. I know that Volvo & OMC made 2 changes to the V6 exhaust system when they changed to the Vortec:
1) changed the angle of the exhaust pipe between the elbow and the Y pipe to more of a sharp right angle to make it harder for water to travel back up
2) added a one way vacuum break valve to each exhaust elbow to eliminate vacuum in the exhaust system, these are one way valves that allow air in but not out obviously.

When I updated my old OMC to the later style exhaust I used the later style exhaust pipes but didn’t have to add the check valves because it’s a pre Vortec but if I repowered this boat with a Vortec V6 then I’d have to add the check valves.

Are you describing Y pipe shutters, which also restrict seawater from getting into exhaust when boat is in reverse?

 

[Lou C]

Nope they used a one way check valve that screws into each exhaust elbow, when a vacuum develops in the exhaust system due to the exhaust pulses of the V6 Vortec engine, this valve allows air into the exhaust, to break the vacuum and stop water from being sucked up the exhaust pipe that connects the elbows and the Y pipe.
See part #27 in this pic...
VP actually discontinued the OMC era design flappers (part # 18) in '99. I still have em in mine though....

 

[Sterling Marine]

Frank

 

[andrewterri]

Thought I remembered reading this somewhere in the manual. Sure enough, you are not suppose to run that engine at idle. I completely forgot. I looking over the manual today and found it so I thought I would throw it up for others to show that what was said about idling on the hose is correct. I forgot who said that, but thank you.

 

[alldodge]

Nice "small" pic, but only states "not" to run above 1400 rpm out of the water. Does state to run motor at 1300 +/- 100 rpm but no indication as it should be done for what reason, only operate at rpm until water is clear

 

[andrewterri]

Nice "small" pic,clear

I am happy I was even about to get it up there correctly. That's what the member that posted that information was saying. That the manual does not explain why you should run at 1300. He than explained why in the fact idling will draw water in. At least that is how I took it.

 

[achris]

I am happy I was even about to get it up there correctly. That's what the member that posted that information was saying. That the manual does not explain why you should run at 1300. He than explained why in the fact idling will draw water in. At least that is how I took it.

That be me, and I be the reason that line is even in the handbook....

Way back when... I owned a boat shop, with a Merc dealership. We sold one of the first Vortec V6s in Australia. When the customer returned for the 20hour service, we found 3 of the spark plugs wet with water. In conjunction with the local Merc state service rep we went through a pile of things to try to get to the bottom of why this engine was getting wet plugs. We removed the heads and checked the gaskets, had the guides for the exhaust valves opened out slightly (thinking an exhaust valve was sticking), changed to a different spark plug, move the timing around, even had a new module from the USA flown in directly with a new timing curve. Had the boffins in Wisconsin working on it. It was they who eventually came up with the engine pulling water through the exhaust. And suggested that raising the idle speed, just for when the engine was on muffs, should solve the problem. And from then on, it was in the owner's handbook.

Chris........

 

[andrewterri]

I am glad you brought that up. That is the last thing I need happening right not. How did it go down with that customer, that had his/her brand new boat torn in pieces :facepalm:

 

[achris]

I am glad you brought that up. That is the last thing I need happening right not. How did it go down with that customer, that had his/her brand new boat torn in pieces :facepalm:

All under warranty. It was a re-power, new engine -> old boat. And we's good. When he got the boat back, he couldn't even see where we'd been.

Chris.......