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Port engine toast?

S

swampyankee

Contributing Member
I've been working the bugs out of the 318s in our 78 Silverton 31. Mostly working past cooling issues. Just when it seemed I might have a good season, what looks like major problems have surfaced on the port engine.

Background is, boat had not been used much in recent years and had been maintained on a shoestring. Records show that the last major work was done around 2007 or so, with only about 250 hours accumulated since.

My first issue with the port engine goes back to fall of '18 when we were taking rev./speed readings up and down the river. Although we were able to rev to 3500 or so, on the last run it wouldn't go past 2500 rpm and was bogging. At the time I thought it might need a good carb cleaning/rebuild. The boat didn't go in the water in '19 as I did some work on it including new manifolds and riders.
We launched a couple weeks ago and have used it a few times since. The port engine has always used more oil than the starboard, and I topped it off with maybe a 1/2 quart before we left the dock. About a 1/2 hour out I noticed the port engine starting to lose power so we turned around. Oil pressure was steady at 40 psi and temp was at 120 f the whole time, but I noticed it getting a lot of blowby under load. When we returned I found a fair mount of oil which appears to have pumped out of the dipstick tube :( and there was alot of oil in the spark arrestor where the breather tube was attached. Starting it back up there was some oil smoke coming out of the breather., although there was no evidence of oil burning out the exhaust, not oil sheen on the water.
I will do a compression test to check for bad rings. If so, that engine is toast, along with our boating season. But would there be a simpler and less costly reason for this to happen?
 
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swampyankee said:
My first issue with the port engine goes back to fall of '18 when we were taking rev./speed readings up and down the river. Although we were able to rev to 3500 or so, on the last run it wouldn't go past 2500 rpm and was bogging.
Is the hull clean and free from marine growth?
Is your ignition system delivering the correct progressive and total spark advance?

At the time I thought it might need a good carb cleaning/rebuild. The boat didn't go in the water in '19 as I did some work on it including new manifolds and riders.

We launched a couple weeks ago and have used it a few times since. The port engine has always used more oil than the starboard, and I topped it off with maybe a 1/2 quart before we left the dock. About a 1/2 hour out I noticed the port engine starting to lose power so we turned around. Oil pressure was steady at 40 psi and temp was at 120 f the whole time,
120* is too low!

but I noticed it getting a lot of blowby under load. When we returned I found a fair mount of oil which appears to have pumped out of the dipstick tube :( and there was alot of oil in the spark arrestor where the breather tube was attached. Starting it back up there was some oil smoke coming out of the breather., although there was no evidence of oil burning out the exhaust, not oil sheen on the water.
I will do a compression test to check for bad rings.
For more accurate data, you will want to perform a cylinder pressure leak-down test.


If so, that engine is toast, along with our boating season. But would there be a simpler and less costly reason for this to happen?
You will learn more with a leak-down test.
Click to expand...
 
RicardoMarine said:
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Click to expand...

My first issue with the port engine goes back to fall of '18 when we were taking rev./speed readings up and down the river. Although we were able to rev to 3500 or so, on the last run it wouldn't go past 2500 rpm and was bogging.
Is the hull clean and free from marine growth? At this point, only in the water for 2 weeks with fresh bottom paint.
Is your ignition system delivering the correct progressive and total spark advance? Not sure about this, but I plan to investigate if compression is good.

At the time I thought it might need a good carb cleaning/rebuild. The boat didn't go in the water in '19 as I did some work on it including new manifolds and riders.

We launched a couple weeks ago and have used it a few times since. The port engine has always used more oil than the starboard, and I topped it off with maybe a 1/2 quart before we left the dock. About a 1/2 hour out I noticed the port engine starting to lose power so we turned around. Oil pressure was steady at 40 psi and temp was at 120 f the whole time,
120* is too low! What would be the cause of this? I have replaced the heat exchanger and water pump impeller, thermostat is present and correct. I will verify temp gage reading with IR gun.

but I noticed it getting a lot of blowby under load. When we returned I found a fair mount of oil which appears to have pumped out of the dipstick tube :( and there was alot of oil in the spark arrestor where the breather tube was attached. Starting it back up there was some oil smoke coming out of the breather., although there was no evidence of oil burning out the exhaust, not oil sheen on the water.
I will do a compression test to check for bad rings.
For more accurate data, you will want to perform a cylinder pressure leak-down test.


If so, that engine is toast, along with our boating season. But would there be a simpler and less costly reason for this to happen?
You will learn more with a leak-down test. If it passes, what could be the reason for blow-by like this?
 
He has given you excellent info, but, I would check your PCV
system first if it is not performing properly, the conditions you have described can be associated with an improperly functioning PCV Valve.
 
Coop88 said:
He has given you excellent info, but, I would check your PCV
system first if it is not performing properly, the conditions you have described can be associated with an improperly functioning PCV Valve.
Click to expand...

Being a 70s boat, I don't think my engines have PCV Valves, just a breather which vents directly into the valve cover. Could the breather be clogged? I will check this as well.
 
Do you have an FSM? It discusses a "Closed Crankcase Vent System" on page 21.
If you need it, a free download via the green "DOWNLOAD" link at the top of the page in the link below. Then follow the directions to download and save as a PDF (15 megs).
[FONT=Verdana,Arial,Tahoma,Calibri,Geneva,sans-serif]https://www.manualslib.com/manual/1007590/Chrysler-Lm-318.html[/FONT]
 
daves69 said:
Do you have an FSM? It discusses a "Closed Crankcase Vent System" on page 21.
If you need it, a free download via the green "DOWNLOAD" link at the top of the page in the link below. Then follow the directions to download and save as a PDF (15 megs).
[FONT=Verdana,Arial,Tahoma,Calibri,Geneva,sans-serif]https://www.manualslib.com/manual/1007590/Chrysler-Lm-318.html[/FONT]
Click to expand...

I looked it up after posting to see what it said. I see the second hose with a PCV valve. I can't remember seeing them on the motors so I will look for it tomorrow. Thanx.
 
This could be the result of too much oil in the engine. Is it possible you have the incorrect dipstick (too short) in your engine and when you fill it to the full mark you have overfilled the engine. My 1972 318s use 6 liters of oil with a new filter installed. I'll measure the length of my dipsticks from the top of the dipstick tube to the full mark the next time I'm down at the boat. If any one else has this information, feel free to chime in.
When you pull the PCV valve out, shake it. If if rattles it's okay. If it doesn't, replace it (cheap).
120 degrees is a little low but won't cause the oil symptoms you discussed. Check to make sure you have a a 160 degree thermostat installed, and swap it with the other engines thermostat if you can. If 120 degrees follows the thermostat replace it. If the problem stays on the port engine the gage could be off a bit.
 
Toonl said:
This could be the result of too much oil in the engine. Is it possible you have the incorrect dipstick (too short) in your engine and when you fill it to the full mark you have overfilled the engine. My 1972 318s use 6 liters of oil with a new filter installed. I'll measure the length of my dipsticks from the top of the dipstick tube to the full mark the next time I'm down at the boat. If any one else has this information, feel free to chime in.
When you pull the PCV valve out, shake it. If if rattles it's okay. If it doesn't, replace it (cheap).
120 degrees is a little low but won't cause the oil symptoms you discussed. Check to make sure you have a a 160 degree thermostat installed, and swap it with the other engines thermostat if you can. If 120 degrees follows the thermostat replace it. If the problem stays on the port engine the gage could be off a bit.
Click to expand...

All good points I will look into tonight when I do the compression test and leak down.
I replaced the stbd thermostat while chasing cooling problems with that motor last season it was in. I was also thinking of replacing the thermostat on the port engine as well.
I had the yard mechanic do an oil change so I don't know how much oil he put in. I do know that it read about 1/2 quart low and that I topped it off before we went out and had the "blowby" problem. Knowing the length of the dipstick and tube would help to see if overfilling could contribute to the problem. IIRC, the port engine was replaced with a long block, and they have been owner-maintained, so who knows if they had the wrong dipstick and just compensated by keeping the oil level low on the stick. I wonder if excess oil being pushed into the intake would cause the plugs to foul and bog down over 2500 rpm, which is the problem that led me to the blowby thing.

The baffling thing is, the engine starts right up and idles smoothly. When I had the yard mechanic look at the problem, he even commented about how nice it was running.
 
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swampyankee said:


If so, that engine is toast, along with our boating season. But would there be a simpler and less costly reason for this to happen?
You will learn more with a leak-down test.

If it passes, what could be the reason for blow-by like this?

The cylinder leak-down test is not a pass or fail test. We already know that there is a problem. The cylinder leak-down test is performed as to help determine where the problem is.
Click to expand...
 
As a follow-up, I did my compression test on the suspect engine. All cylinders had between 140 and 150 psi except number 5, which barely had 30 psi. Checked, re-checked, and added oil to cylinder and rechecked which yielded a temporary increase to 60 psi. At that point, it doesn't matter what a leakdown test could show. No matter what the case, it would require a tear-down, which is work and expense I am not willing to expend on this boat.
As luck would have it, a gentleman was asking about the boat. He and his wife really like the boat and he is willing to do the repairs so we agreed on a fair price as-is.
 
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