Engine burns excessive oil at high RPM's

Post here if you want to discuss a topic specific to the MV/32, MV/34, and MV/41.
User avatar
AMCarter3
admiral
admiral
Posts: 174
Joined: Thu Apr 21, 2016 8:32 am
Location: Bellingham, WA
Contact:

Engine burns excessive oil at high RPM's

Postby AMCarter3 » Sun Aug 13, 2017 1:00 pm

We're trying to figure out why our PORT 100 HP Yanmar engine burns excessive oil when run for long hours at at high RPM. For example, when the boat is operated for 4-5 hours at about 3200-3400 RPM (about 14 Kts), our Port engine can burn up to 1 qt of oil per day. When the boat is run in a normal cruising mode (1800 - 2200 RPM), it does NOT burn excessive oil.

We had the Port engine evaluated by our local Yanmar diesel maintenance company recently. After a series of tests (including "Base Pressure"), they reported the engine is "normal" in all respects... no visible oil leaks... no apparent internal damage to valves, rings, turbo, etc. In fact, it seems to perform almost exactly the same at max RPM as the Starboard engine (which does not burn excessive oil when run at high RPM's for long hours). Yet the Port engine does burn substantial oil at high RPM's for long hours. The dealer said the engines are being stressed if run this way and should be run at no more than 80% of max rated RPM (roughly 3000 RPM).

Anyone else have one engine that burns excessive oil when run for long hours above 2800 RPM? If so, did you learn why?
Mac Carter
2006 34' PDQ PowerCat "All Heart"; MV 98
Bellingham WA

deising
admiral
admiral
Posts: 151
Joined: Mon Sep 15, 2014 3:48 pm
Location: Punta Gorda, FL
Contact:

Re: Engine burns excessive oil at high RPM's

Postby deising » Sun Aug 13, 2017 1:53 pm

Well, it is interesting that it is your port engine. I say that because 95% of all the engine woes I have had in 10,000 plus miles have been with the port engine, and I know a number of other PDQ 34 owners who say the port engine gets way more than its share of problems compared to the starboard engine.

Two things to mention:
1. Some owners will dispute this, but several owners, including Dick Tuschick, have noted that they consider the middle of the full and low marks on the dipstick to be "full." In the beginning of our ownership, I noted that I lost the oil from the top of the dipstick mark to the middle pretty quickly on both engines, although the port was much quicker. On the starboard engine, when I fill to the middle level, it takes 60-80 hours before I need to add another quart. Of course, 80% of our running is at 2200 RPM or so (75HP in low speed mode). If I cannot explain it.

2. The port engine started losing oil to the tune of 1 quart every 10 hours, but not necessarily more at high speed (again, we don't run high speed very much). It was not leaking into the engine bilge, nor appearing as blue smoke, at any engine speed. I finally realized I had a small leak where oil was pushing past the o-rings in my oil cooler into the raw water and then exiting with the exhaust. The oil pressure is greater than the water pressure in the cooler, so the leak only let oil out, not water in, thankfully. Removing the cooler to replace the o-rings was a major pain, but that slowed the leak considerably.

I don't know if either observation helps in your case, but it is more info for your consideration.
Duane Ising
m/v Diva Di
Punta Gorda, FL
2006 PDQ MV 34 - hull 91, 75HP, 3-blade

User avatar
SecondWind
admiral
admiral
Posts: 389
Joined: Sat May 08, 2004 8:57 am
Location: Punta Gorda, Fl (33950)
Contact:

Re: Engine burns excessive oil at high RPM's

Postby SecondWind » Mon Aug 14, 2017 6:59 am

A compression test may be in order. Since Diesels are oil burners there may not be any blue smoke. In addition to the leaks Duane mentioned, the other possibilities are worn valve seals and/or piston rings.
Terry Green
s/v Second Wind
36040

User avatar
AMCarter3
admiral
admiral
Posts: 174
Joined: Thu Apr 21, 2016 8:32 am
Location: Bellingham, WA
Contact:

Re: Engine burns excessive oil at high RPM's

Postby AMCarter3 » Mon Aug 14, 2017 3:24 pm

These comments are really helpful and appreciated. Based on their testing so far, our local Yanmar diesel folks (the best in my area) have tentatively ruled out compression issues, bad rings & bad valves as the source. In fact, they found the Port engine is performing virtually equal to the Starboard engine and well within the performance specs, despite the fact that it burns oil when the boat is run at high RPM's for long hours.

I was very interested to read Duane's comment about the tiny oil leak in the 0-rings inside the oil cooler. The diesel tech that did the recent "Base pressure" test, suggested that as one of two possibilities. The other was the turbo system - he opened it, thought it looked "OK", but said it "might" benefit from being rebuilt. I'm going to share Duane's comment with them.

Thanks!
Mac Carter
2006 34' PDQ PowerCat "All Heart"; MV 98
Bellingham WA

deising
admiral
admiral
Posts: 151
Joined: Mon Sep 15, 2014 3:48 pm
Location: Punta Gorda, FL
Contact:

Re: Engine burns excessive oil at high RPM's

Postby deising » Wed Aug 16, 2017 12:08 pm

Mac,

I am glad you mentioned the turbo. I must have repressed that horrible memory. The previous owner had the port turbo rebuilt and a yard installed it, probably very soon before it went up for sale in fall of 2014. Very shortly after I got the boat, but after the sea trials and survey, I noted a massive oil consumption on the port engine (like 1 quart an hour). I traced it to a bad oil seal on the intake air side of the turbo.

The 50psi oil pressure was gushing oil past the seal and into the intake manifold. The engine burned it, with some degree of blue smoke, but it needed fixing ASAP. When I took the ducting off between the turbo and the intake manifold, I placed a metal can underneath and with the engine running just above idle, the oil leak was quite evident.

The yard (Stuart Yachts) stood behind their work, even though it was rebuilt by a third party, and sent me a brand new turbo to install. I thought that was first class. No problems with the turbo ever since (1,200 hours hence).

Again, good luck.
Duane Ising
m/v Diva Di
Punta Gorda, FL
2006 PDQ MV 34 - hull 91, 75HP, 3-blade

User avatar
AMCarter3
admiral
admiral
Posts: 174
Joined: Thu Apr 21, 2016 8:32 am
Location: Bellingham, WA
Contact:

Re: Engine burns excessive oil at high RPM's

Postby AMCarter3 » Wed Aug 16, 2017 1:14 pm

Wow, Duane! That's a great story pertaining to my situation. I'm sure it was frustrating for you even with that great service you got from Stuart Yachts, but a good outcome.

Our Port engine is not consuming that much, but it is concerning -- about 1 qt per day if run at high RPM's for long hours. And, now I've got some degree of confirmation from this forum that the source of oil consumption could be either the O-ring in the oil cooler or the oil gasket seal in the Turbo. I'm passing this along to our Yanmar maintenance guys.

Thanks so much... very helpful.
Mac Carter
2006 34' PDQ PowerCat "All Heart"; MV 98
Bellingham WA


Return to “PDQ Powercat Forum”

Who is online

Users browsing this forum: Bing [Bot] and 1 guest