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Joined: 8/24/20
Posts: 2
M35 Crankcase Breather Blow By

i have found a really nice 2000 C36 MKii for sale that had a problem uncovered by the survey. It has a Universal m35B engine with 455 hours that is likely original to the boat. The surveyor described it as moderate crank case blow by. Smoke from the breather tube was white in color and started appearing at about 2000 rpm and increased up to maximum revs. The breather tube is not oily, just the blow by and the white smoke. The engine started started up easily and made good power driving the boat close to 7 knots into a 30 knot headwind at full throttle.  Judging by the condition of the boat and the low hours, I do not think this engine has been run very hard. 

For or those that know this engine is this somewhat normal or an indication to run the other way?

I am am wanting to get into a C36 and I thought I had found a good boat, now I have doubts, help!

Catboat Willy's picture
Catboat Willy
Joined: 12/22/14
Posts: 317

 This is a little hard to analyze via this forum but a certain amount of white smoke out of the breather tube is to be expected as the engine heats up. How hot was the engine when this was happening and when was the last time it was used ? It of course begets the question, how much smoke ? I am guessing that the breather tube is not terminated in to a oil catch container. If the boat had not been used in a while, there may have been some water in the oil system.
Two observations:
One;  455 hours seems like a very small amount of time for a twenty year old boat. 22 hours a year ?
Second; Before you spend that amount of money on this particular boat, hire a diesel mechanic to look the engine over. If you pay him $100 and hour, it will be well worth it.
To rebuild an M-35 engine will cost you in the neighborhood of $5,000. plus the hassle and time of extracting the engine and then re-installing it. In my experience, surveyors usually have to find something wrong with any boat they are surveying or you will not feel they are worth their fee. (no offence intended). Seldom if ever does a surveyor say ' 'This is a perfect boat' and usually leaves you with a bargining chip when buying the boat.
Try and find a diesel mechanic and let him evaluate the engine for you. Diesels that are used frequently, such as farm tractor engine that are used on a daily basis, are usually good for 10,000 and 20,000 hours. Engines that are seldom used seem to have a shorter life. ........ Good luck with your decision.

Siler Starum's picture
Siler Starum
Joined: 4/20/18
Posts: 66

First: A C36MKII is a perfect boat... no  conserns and no doubts about that. Believe this from a 2001 C36MKII user.
455 running hours for a 20-year boat is indeed not that much and if these hours are real you might have an issue caused by some internal corrosion because it hasn't been used so much. Sticky pistonrings??
Friendly spoken we had to do an overhaul of our M35B (1400 hrs) when we bought our Siler because of leaking cylinderhead gasket and a failure of LO-pressure sensor, but all to overcome and since the repair: "hit-and-run" and realy a reliable engine.
We forgot already the additional costs for the repair.... 

Joined: 10/22/18
Posts: 198

My 1999 only had 484 hours of time on the Tach, which seemed way too low to be accurate.  And as my surveyor said, the only thing the timer on the tachometer tells you is how much time is on the tachometer.


alfricke's picture
Joined: 4/14/09
Posts: 49

Jubilee is a 2000 mkII #1867. I've put about 2000 of the 3000 hrs she has on her and know her well. I've never seen what you are describing, doubt that it is normal. Like others I'm guessing it is from lack of use. Good diesel mechanic is the way to get your question answered...could be a relatively inexpensive fix and you'd have a great boat!!!

Haro's picture
Joined: 11/7/14
Posts: 283

Hi all,
I purchased my 1999 C36 10 years ago with 540 hours on the engine. Today it has 1300 hours on its display.
I have used it regularly, at least twice a month. I sail from San Francisco to Santa Cruz at least once a year and in most cases this 240 mile round trip turns out to require 75% of the time to just engine, due to low or no wind, usually when going back to north. Each 120 miles takes about 20 hours.
Currently my boat is in Santa Cruz as on the way back I had to deal with 8 to 10 foot waves and 40 knot head winds. So engining was the only way to move. Half way to Half Moon Bay - about 30 miles North of Santa Cruz, the engine RPM suddenly dropped from 2000 to 1000 and I heard loud pounding noise from the engine room. So I dropped to idle speed and placed the gearshift to neutral. The engine continued to run in neutral. So I reved up to see if the engine was having trouble - it reved up with no problem. Then I lowered to idle RPM and placed in forward gear and it started to moved forward. But as I increased the RPM to 2000, it started with the same loud knocking sound. Since the wind was blowing south I decided to return to Santa Cruz by raising the main at any way that I could.
I found that I could use the engine to propel the boat as long as I kept the RPM below 1500. I was able to re-enter the harbour and doc on my own power.
Today I went back to find out what I could find wrong. I ran the engine and heated it up to normal 160 F then put it in gear and reved up the engine to 2000 RPM for over 10 minutes.
The only thing that I noticed was there was blue smoke coming out of the breather tube - a light amount. I never heard the loud knocking sound. Everything worked as normal.
Interestingly enough today I found this post about the fumes coming out of the breather tube.
So what is the expected answer? Blue smoke spells trouble? I checked the oil level and it was normal. I am thinking that it appears to be burning oil. Or is this normal. If I could guess I would have to add one quart of oil per 2 months. There are no oily regions near the breather tube as the nearby air filter sucks the smoke in.
A white smoke would mean steam - I would think it is evaporating the moisture in the oil and it will stop when warm.
Has anyone observed their engine under load at 2000 RPM? Is there blue smoke coming out of the breather tube?
I am 120 miles from my home port. I would like to be able to engine back home where I can get help. Is it likely that I will be successful?
What are my choices?
I am also thinking that the engine may have been operating at heavy load and it could no longer handle the load due to large waves and high wind. The water temperature was always normal.
Thanks for your feed back.

pkeyser's picture
Joined: 5/18/13
Posts: 462

Unless you are consuming oil (blue smoke out the exhaust) or blowing white smoke out the exhaust (antifreeze/water), I would tend to think the engine is OK. Loud banging can be caused by a fouled fuel injector, or bad fuel (among other things). How does your fuel look? Any water and algae in the separator? Sometimes an injector issue will resove itself or be intermittent. Powering through rough conditions can break free sediment and contaminents in the tank. 

Haro's picture
Joined: 11/7/14
Posts: 283

pkeyser - you were correct about stirring up the crud that caused the blockage and fuel starvation. I was able to clean the residue that was accumulated in the trap under the primary fuel filter bracket and it is all OK now. The breather tube light smoke was normal.
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pkeyser's picture
Joined: 5/18/13
Posts: 462

Thanks for sharing your findings. Glad it was an easy fix!

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