Trojan Boat Forum

it is a Jasper reman, 1976, electronic ignition and it is knocking. It is not a metallic tapping, just a knock. It comes from the top end (stuck my screwdriver on the bottom end and listened).

She has excellent oil pressure, checked the oil level as well, and fresh oil and filter. It concerns me now as she died on me, while docking yesterday, and was hard to restart. The two may be mutually exclusive, but now I am taking a harder look.

My to do list:
Check EGR valve
Swap out ignition module with known good spare
pull valve covers and look for loose things

It sounds exactly like YouTube - ‪g35 engine knocking badly‬‏

Any eye deers?

I hope the sound is different then the U tube clip. You should not have a EGR valve on it . Hopefully just a bent push rod or something simple like that. With out hearing it in person its hard to say for sure .

will the noise change in and out of gear ? go away at different rpms ?

There should be no exhaust gas recirculation valve ( egr) on your boat's engine. If so...someone has put a car engine in at one time, or car manifold on it.

Paul and Jamie - you sure about the EGR valve comments? My original '79 360's have them.

Heefus - Can you at least tell which bank is making the noise? Before you pull stuff apart, pull the plugs on that side and look for a wet one (water, not oil or gas)...

A few years back I had a cracked manifold that started out as a knock, then led to rough idling, then engine quitting and refusing to turn over. You could have the same, or perhaps just gasket gone bad. For me things were fine as long as I was cruising, but every time I shut down two cylinders would ingest a bit more water. Got harder and harder to re-start, ran rougher and rougher at idle until she finally quit.

Hope that ain't it, but an easy check before reefing on the big wrenches.

That YouTube v6 sounded awful. Like it had no oil (or it was a diesel) - probably a bad rod there Wife ran her van oil super low once - ruined the main bearings and 2 rods. Sounded like that.

Pulling the valve cover is the best choice - assuming the poil level is high (but not overfilled).

No metal in the oil?
Did she overheat recently?
New sound this Spring?

Well, I'll tell ya.

She is not hard to turn over, just hard to start. That pretty much tells me that I am not suffering from hydrolock, though I am going to pull the plugs tomorrow (it was way too hot yesterday). Also, no water in the oil (no foaming)

It is not on one side or the other. All I can say for sure is that it is limited to the top end. When RPMs go up, so does the sound. It is not as loud as a diesel, but it is loud enough for me to hear through the hatch. She doesn't stutter or hesitate and, up until yesterday, had zero issues starting, running, etc.

I was fixin to do plugs and wires anyway, so I will pull them all tomorrow and take a gander. I am a pretty good wrench, but I learned on Fords, live for Toyotas, and can tear down a Chevy. Every manufacturer has their own nuances, and I figured I'd reach out as I am in no way a Mopar man

There are only 2 things I did differently this weekend:
1.) Added fuel (with marine Sta-bil)
2.) Ran her up on plane back to the marina. About an 8 minute ride.

I have a spare re-built block, and a spare set of heads...I am just not looking forward to trying to pull the motor by this weekend, and I am hoping for an easy fix

Quick checks:

1) Check timing (did the distributor move on your 8 minute jaunt?). It its loose, it can rotate around and retard the timing.

2) Check compression.

3) Use In-Line Spark tester to check each wire's spark (just assume plugs are OK - usually OK on 4-stroke, sometime 2-stroke burn plugs).

4) Pull Valve Covers and look (while running - oil may run down side of motor - not sure on Mpoar? but do;t rev it - it will spray!).

5) Pull the plugs and turn by hand to check for rod issues.

Had a bad cam lobe once and it made some noise, but mainly loss of power.

Good luck!

My 78 318s do not have EGR valve, one even has a label on the rear that this is an industrial engine not for road use, ergo no egr. As I have presently four engines 2 new ones and two 900 hour engines that run, albeit one has a crack in block from freezing. I will have lots of extra parts to keep or dispose of.

You probably have a crankcase ventilation valve.

Had a similar sounding friend's 318. Does it happen constantly at all RPM ranges or just when you quickly throttle down? Harder to tell at higher RPM? My friend's sounded to me that it was top end too but bottom end noises can transfer to top end easily. One piston was slapping on power stroke. Found the piston by hooking up a timing light to one cylinder at a time until I found one that fired about the same time as the knocking. This confirmed bottom end to me. Ended up being the suspected piston.

here's something that takes only a few minutes...... swap out the coils and give a listen. Had a similar prob on a race boat engine.
Just a thought, since you said it didn't sound like metal against metal, and only takes a few minutes.

Ron

RB,

Good tip - weak spark can cause detonation (sounded like a diesel in the YouTube video) ... check the timing too - might have rotated and just be off when you ran it this spring.

Ok...

I believe it to be on cylinder 7. I found carbon blow by deposits on the head, just below the gasket. I didn't have my compression gauge with me, nor did I pull the plugs ( I was fighting the oil filter for 2 hours, but that is another story).

I pulled the valve cover, and narrowed the sound down to that cylinder. No bent rods, oil flow is good. I did manage to introduce water into the oil (don't ask, it is what led to the unscheduled oil change) but it was clean prior.

Next week I am going to pull the manifold and take a good look at the head and plugs. We are going out tomorrow, for the day(grand total of 6 miles round trip) and I am going to run her at 8mph to stay on the safe side.

Further updates as events warrant.

Any chance its just a blown exhaust manifold gasket ?

Well my 2nd choice was intake manifold gasket, that caqn cause that sound, but not sure now if you've narrowed it down to one cylander

Ron

prowlersfish wrote:Any chance its just a blown exhaust manifold gasket ?

Definitely a possibility. My water tank keeps me from sticking my head in there, so I had to use some contortionist skills and a flashlight.

Nothing is ruled out at this point. All I did was find the source of the noise.