jsoderbe

Hi Guys,

I went out with the boat today, and the boat (2001 Monterey 248 LS), is fairly new to me. It has been running fine for 3-4 hours with few people, half tank of gas an no water in it. The only thing I have seen is that the temp gauge move from 160 to 190 degrees when I drive 25-30 Mph for more than 15 minutes.

Today I filled the gas tank full (85 gallons), filled the water tank to full, and filled the boat up with 5 more people of varying age. I estimate that I added 8-900 lbs from the last uneventful run two days ago.

So, it was pretty slow up on plane at the first 25 mph-zone here on the Intracoastal, but ran fine. When I pulled back on the throttle entering the next no wake-zone I heard the knock. Didnt think much of it but new sounds are always scary.

When I tried to plane the next time the knock didnt go away, and the boat was really slow to go up on plane. The noise stayed until I pulled the throttle back leaving the boat moving at 1500 rpm. During this time the drive (Bravo 3) was trimmed fully down and the steering was straight ahead.

It was a metallic knock, I have heard pinging before but this was very very loud for a ping. On the other hand I havent really heard pinging in a boat before.

The people in the rear seat said that there was a vibration on the same time as the knocking, but they dont know if it was the reason for the knock or a symptom of it. I think there might have been a vibration there earlier, when going up on plane.

The boat ran fine all day on the intracoastal, but I kept it under 1500 rpm. It starts fine, runs fine, uses no oil, no smoke or anything. No noise at all.

When I came back to the dock I let it run on idle, and the right riser was too hot to hold my hand on. The left riser was warm but I could keep my hand on it. Not so with the right one, especially when I raised the idle to 3000 rpm.

Then I removed the plugs under the manifolds, and the water flow seemed to be even on the left and right side manifold.

So, any thoughts what this might be? Is it drive noise or engine noise? Any ideas would be very appreciated....


Regards,

Johan

F-2 Speedy

iTrader: (6)

My initial thought was bad fuel, detonation under heavy load, but with the excessive heat on one bank, my be head gasket, pull the dip stick and see if there's any water in the oil.

SB

iTrader: (1)

Very possible it's a ujoint / coupler, or rare but happens harmonic dampner coming 'unglued.'

When looking at the frt of the motormotor, it is not uncommon for the right exhaust to be warmer/hotter than the left.

1st thoughts was motor.....but I'm not so sure by your description. Also, 900lbs makes a big difference on planing no matter what motor you have,,,,,but huge difference on a small block motor.

Trash

I'm guessing its drive related but you also have an exhaust cooling issue. You should be able to touch them when the motor is running.

Have a service shop perform drive service and I'd also check all the cooling lines etc.

Jonesyfxr

iTrader: (1)

A cracked flywheel can make a knocking coise that sounds like a rod knock.

jsoderbe

Thanks guys, very appreciated.

The oil is clean as far as I can see, but it could be a head gasket. Or burnt valve? It does sound like a rod knock, but why now after it has been running great for 3-4 hours?

Does the 5,7 EFI have a knock sensor?

It might be the flywheel/damper, due to the vibrations. Would a U-joint make noise going straight with trim down?

So I guess I should start with replacing the risers?


Regards,

Johan

jsoderbe

Hi, just a brief update before seatrial; I replqced both risers and manifolds. The left side is now very nice and cool, but I still feel the right side is too hot. I can keep my hand on the riser but it isnt comfortable. I am guessing it is maybe 140-150 degrees, while the left is maybe 100-110 degrees. Is it really supposed to be that big of a difference, or is something wrong?

I checked the flow and I cant se any difference between left or right water pressure/flow. I removed the drain plugs under both manifolds and there are no difference between them.

Could something be clogged after the riser? Or is my way of testing the flow not ok?


Regards,

Johan

Trash

I know SB stated one manifold can be warmer than the other, and I'm not saying that isn't so. But I have never noticed a difference between both sides and they are usually cool to the touch when running and NOT warm. There should be a continuous large volume of water passing through the manifolds, risers and elbows at all times. It is possible that a piece of debris may have balled up one of the passages in the manifold or elbow.

Jonesyfxr

iTrader: (1)

Maybe your water pump is on it's way out?

Blueabyss

I would replace water pump just as a general maintenance particularly since you had a temp of 190. Can you take a pic of the old manifolds and risers so we can see what they look like? Also many EFI apps have restrictor gaskets between the risers to actually bring temps up. If you have the wrong gasket on one side it could flow too much water to one side and starve the other side. I have had some apps that it was just always hot on one side and cold on the other so I removed the restrictor gasket on the hot side and it cured the problem . Not that thats a proper way to fix it but it worked. Does yours have the t piece on the thermostat housing with check balls? As for the noise, I have no Idea except that engine is computer controlled with knock sensors so I dont think it can ping or knock. You would just feel a shudder as the computer pulled timing.

Chris