Pirate
New Member
And it runs on red diesel.
QSM-11 Intake blow-by/bolt missing
- Thread starter Four Suns
- Start date
To finish the story here, the port engine is back together, cleaned, and painted and performs great now. Both engines accelerate at the same rate now and the boat gets on plane quickly. Boost pressure on the port side engine is still a little lower than the starboard engine at WOT (73-74 in Hg vs 76-77 in Hg) as shown on the digital gauges. Everything looks airtight so I'm assuming other factors have the boost a little lower on the port engine. The port engine gets its air from the middle of the engine room (hot air) whereas the starboard gets its air right by the hull vent (cool air)... When I took these WOT boost readings a few weeks ago before the fix, it was pretty hot out and the starboard would only get to 73 in Hg and today it was much cooler (by 20 degrees) and the starboard is up at 77 in Hg. Frank W. is going to tell me I'm over analyzing this again... Looking at the primary gauges, the thing performs perfectly so I'm just going to go boating.
Last edited:
Nehalennia
Well-Known Member
- Aug 22, 2007
- 10,006
- Boat Info
- 2001 310DA twin 350 MAGs, Westerbeke 4.5KW
- Engines
- Twin 350 MAG V-drives
Gary
I think the black you are seeing is the residue from the gasket vibrating itself to death and adhering itself to your manifold and block. With new gaskets and new bolts all teh way around, hopefully everything is ok.
Best of Luck
I think the black you are seeing is the residue from the gasket vibrating itself to death and adhering itself to your manifold and block. With new gaskets and new bolts all teh way around, hopefully everything is ok.
Best of Luck
PartnerShip
Member
Gary
There is a simple test to see if your engine room is "starving for air". While running at crusing speed open the hatch cover in the deck of your cockpit. If you feel a suction when you first open it you have an "air starved" condition.
Also, with this hatch open again check your boost readings at WOT. You might be suprised!
Joe A
There is a simple test to see if your engine room is "starving for air". While running at crusing speed open the hatch cover in the deck of your cockpit. If you feel a suction when you first open it you have an "air starved" condition.
Also, with this hatch open again check your boost readings at WOT. You might be suprised!
Joe A
That's a good idea! I'll do that as the port engine airsep would be right by the hatch and would verify if the difference is due to location in the engine room. It's more of a curiosity right now as they are both running great (knock on wood)...
PartnerShip
Member
Did this today. Today at WOT, the starboard engine had 74 in Hg and the port engine had 70 in Hg of boost. Had my wife open the hatch and the port engine went to 74 in Hg. Closed the hatch, and went back to 70.... It was hot out today so I assume that's why I didn't get the 77 like I did the other day. Load factor and fuel burn also ended up closely matching the starboard engine with the hatch open whereas it is usually 2-3% higher on load and about 0.5 - 1.0 gph higher with the hatch closed...
hmm....
Engines run great and you only know this by looking at the boost on the guages...
hmm....
Engines run great and you only know this by looking at the boost on the guages...
osd9
New Member
Would running with the blowers on help?
The blowers suck air out... hot air...
I think that would be like trying to put out a grease fire by peeing on it.
I just think the intake of the port engine being smack dab in the middle of the engine room as opposed to next to the hull vent like the starboard deminishes performance a little. The engine room is hot even with the blowers running and the port engine is sucking hot air as opposed to cooler outside air.
(I had the blowers on today)
I think that would be like trying to put out a grease fire by peeing on it.
I just think the intake of the port engine being smack dab in the middle of the engine room as opposed to next to the hull vent like the starboard deminishes performance a little. The engine room is hot even with the blowers running and the port engine is sucking hot air as opposed to cooler outside air.
(I had the blowers on today)
PartnerShip
Member
Gary
I had a very similar problem with my Cummins 450C's in my 400DB. At WOT, turning 2750 RPM's, and fully loaded I had only 72 Hg port and 64 starboard. I ran plastic bilge blower hose from the outside air vents in the hull to the center space in the engine room. About middle way we installed a 12 volt bilge blower blowing fresh air in. We wired this in parallel with the existing bilge blowers.
Now with the blowers on we have a constant supply of cool outside air and my boost is running around 78-80 on each side.
Joe A
I had a very similar problem with my Cummins 450C's in my 400DB. At WOT, turning 2750 RPM's, and fully loaded I had only 72 Hg port and 64 starboard. I ran plastic bilge blower hose from the outside air vents in the hull to the center space in the engine room. About middle way we installed a 12 volt bilge blower blowing fresh air in. We wired this in parallel with the existing bilge blowers.
Now with the blowers on we have a constant supply of cool outside air and my boost is running around 78-80 on each side.
Joe A
ImpulseIII
Active Member
Gary,
You need a "cool" hood scoop like they use on supercharged drag cars.....Maybe with a flame paint job...yeah...that'll do it!!
You need a "cool" hood scoop like they use on supercharged drag cars.....Maybe with a flame paint job...yeah...that'll do it!!
osd9
New Member
FLOMAX....
The first thing I'm going to do is check the vent holes on the boat and see if they are clear. It'll be my luck some creatures (like birds or mud daubers) have built nests in there. If it's clear, not sure I'll do anything. It doesn't seem to be a problem but more of something that just shows up on the guages. I did think about some kind of overhead pipe and a blower but getting a blower/pipe capable of matching the CFM of air the QSM-11 sucks in would be rather large IMO.
And yes... for a second I did think "what this boat needs are some scoops"... no painted on flames though...
And yes... for a second I did think "what this boat needs are some scoops"... no painted on flames though...
I just checked the CFM rating on the QSM-11 and it is about 1500 CFM. The 4" marine blowers in my engine room are rated at 250 CFM... I think to get a meaningful cool air input to the engine room middle would require some fancy plumbing and blowers... not worth it IMO...
Off to the boat... pretty day today in VA
Off to the boat... pretty day today in VA
