[trantor12020]

On average I do 130 engine hours per year. Its total hours is 1550hours now. This isn't alot ...is it?

 

[christian.hess]

do you use it every day? or every season?

the reason I say this is its quite possible that you do have a bad head gasket or whatever but since you never use the engine till its really hot and used you will never know

plenty of engines run around with leaks in the cooling passages, and smoke a bit then burn off, etc...

I had a truck with a cracked head...never used it till it got to full operating temp and just topped off every once in a while

until it finally cracked(the gasket completely blew) and I just soldered up the passages later on

what would a typical day of engine use be for you?

15 minutes out 15 minutes in?

1550 inst massive but it could be enough to warrant a rebuild cause it all depends on previous maintenance or lack thereof

it only takes running low on oil once or twice for you to be able to damage rod bearings and or pumps so hours alone wont tell you much

 

[dabnis]

On average I do 130 engine hours per year. Its total hours is 1550hours now. This isn't alot ...is it?

Generally speaking, I don't think that is a whole lot? There can be lots of variables like the frequency of oil changes, coolant in the oil, overheating, & so on to consider. Properly maintained diesels can run along time.

The commercial fishing boat we had, below, had many thousands of hours on it, as best as we could tell, and ran fine. It was a Detroit 2 stroke 3-71 diesel, aka "screaming Jimmy" Lots of variables to consider.

Maybe try a prop with enough pitch to "bog" it down and then re-pitch just enough to reach maximum RPM?

Paul T

 

[Minnewaska]

A diesel needing an overhaul at 1,550 hours over 12 years, without being abused or severely overheated, is about as common as a 30 year old getting Alzheimer's.

While it is most common for coolant to leak into the engine oil and cause the milky telltale, if the gasket leak is near a higher pressure location, the oil can leak into the coolant instead. Since it hasn't been changed in so long, I would drain it and take a look.

 

[christian.hess]

your right minnewaska...absolutely but going by hours alone is useless...you dont know if it HAS been abused, or improperly maintained at any point

op are you the original owner? have you done all the maintenance on said engine?

 

[trantor12020]

I'm the original owner. In early years I don't know much about diesel so within 2 years I choke up the U Mixing Elbow with enough coke & rust to stop the engine running. Got engine fixed in workshop. Shouldn't have to actually. As I learn more of diesel, I guess I got careless/complacence. 3 years back discover only about 1 litre oil in engine after a 500nm passage. Silly me for not checking. So I might have caused excessive wear in rings.
As maintenance, I change oil & filter every 100 hrs. Oil turns black after couple hrs of driving. Not sure if that's normal or results if wore rings. No water in oil so far. Only oil sheen on water at stern when at berth, yet to confirm if from my engine or others.

 

[christian.hess]

rebuild it...those 3 things you mention would make me do it at least

without getting into details I dont know why a new engine could get coked up and rusted so quickly

its possible right there that you damaged and pitted at the least exahaust valves

but you say you took it to a shop so it got fixed

cool

the low oil could damage rings if run for a while like that, you can also score the liners/cylinders as well causing you to burn oil...

the oil turning black quickly is common...however after only a couple of hours is a bit much in my opinion...

in any case...thats my recomendation

a quick well done refresh with a rebuild kit will also get you any lost power back, improve fuel consumption, noise, etc...etc...

good luck

 

[trantor12020]

Back then, I was nursing a brand new engine initially. Running on low rpm mostly. Didn't know diesel engine loves S&M that much.

 

[Minnewaska]

......within 2 years I choke up the U Mixing Elbow with enough coke & rust to stop the engine running. Got engine fixed in workshop. Shouldn't have to actually. As I learn more of diesel, I guess I got careless/complacence. 3 years back discover only about 1 litre oil in engine after a 500nm passage........

:laugher well, goodness. That's a problem. Would have been useful to know.

 

[christian.hess]

Back then, I was nursing a brand new engine initially. Running on low rpm mostly. Didn't know diesel engine loves S&M that much.

gotcha

its easy to coke up, now the rust? why? you not have a good waterlift or you got heavy seas backing into the engine or what?

 

[trantor12020]

Rust from the cast iron U Mixing Elbow. Heat+seawater+iron+sulfur in diesel not good I suppose.

 

[christian.hess]

ok just normal use then

ok well I think you have options on what to do...some of your issues we now can assume were caused by the things you just mentioned...

the low oil is what I most am concerned about...simply put it could be the cause if scored cylinders...do you hear slap or knockingwhen starting up?

this in turn causes lose tolerances so the rings get lose...once they losen up beyond a certain point the lands are way too apart...and you can get oil passing by and not sealing well

honestly its not a deal breaker

use thicker oil, stp and call it a day or prep for a rebuild

it doesnt seem you have any issues with the heat exchanger, coolant etc but in a rebuild something will always show up, be it a slight passage clogged up or a little tear in the gasket...etc...

 

[trantor12020]

If there's any knocking, I'm not aware or able to discern. Great we've narrowed down to some actionable items. Heavier weight oil is one that I'll do. I've a can of STP on hand.
Appreciated.

 

[dabnis]

If you can still pull 3,300 RPM the engine must still have some beans left in it. What would it pull originally? Unless your oil pressure dropped significantly on the long run & the engine didn't develop a death rattle, it still may have some life left in it?

If it won't pull the same RPM as when newer, with the same prop, then it may be getting tired. Maybe try a higher pitch prop until you bog it down & then adjust the pitch accordingly?

Paul T

 

[christian.hess]

exactly you can alleviate a lot of the strain the engine is currently having by lowering pitch(after you try a high pitch one to bog it down and know where) therefore allowing the engine to gain a bit more torque, also you might increase your cruising revs up

but hear me out, you will not gain speed...you will gain torque...meaning the engine will improve the torque it has usually in midrange or cruising rpms and slow manueviring, in most cases you lose topspeed but gain considerable rpms where you need it...

this will alleviate the engine a bit and not load it up to where its fighting to keep up rpms

its a good choice since the engine is a bit tired but by no means trash...

dabins posted a good question

whats your oil pressure? do you even have a gauge? not just the idiot light yanmars come with?

you can learn a lot from how tired an engine is by simply looking at oil pressure at startup and then how it lowers when warmed up...if its drastically lower in normal range again you can experiment with stp, thicker grade oil and the like as it will tighten up tolerances a bit and thats that

a good way to prolong the rebuild...

cheers

 

[dabnis]

you can learn a lot from how tired an engine is by simply looking at oil pressure at startup and then how it lowers when warmed up...if its drastically lower in normal range again you can experiment with stp, thicker grade oil and the like as it will tighten up tolerances a bit and thats that

a good way to prolong the rebuild...

I experienced that exact situation with my daughter's VW turbo diesel. After about 60,000 miles when doing a long hard climb the oil pressure would drop from about 60 lbs to about 20 lbs at speed. at idle it would go down to about 5 lbs, triggering the red light. It never rattled or knocked, just scared her. Tried heavier oil, no change.

It didn't burn any oil to speak of & ran fine. Could have been a worn pump, or a bad pressure relief valve, but probably was the main bearings slowly going away?

All that being said, I think it would be easier to do some prop swapping before ripping the engine out?

Paul T

 

[Minnewaska]

Being over propped could be what coked the elbow up in the first place.

 

[christian.hess]

yeah guys agree...

hope any and all of this talk actually helps the op some!

 

[dabnis]

Prop I used are: stock 2RH 15"Dx10"P, CSP 3RH 14"Dx9"P, & 7"P, & 6"P, KiwiP 3RH 16"Dx20deg, & 18deg.
I've tried SAE40 and SAE15W40. I don't find any difference. I've tried adding STP Oil Treatment (Silicone base). It helps raise max rpm by 100-200rpm.

If you could pull 3,300 RPM with all of these props perhaps none of them had enough pitch or diameter to indicate you were/are "over propped"? The only way I can think of telling how much pitch/diameter is too much is to find a prop that will not let the engine pull to its maximum RPM ?

Paul T

 

[Minnewaska]

and....... if the OP doesn't figure out how to get the WOT rpms back to the proper level, this may all repeat itself. Without that fixed, every other suggestion is temporary.