At wits end Runs great for 20miles then knocking then sputtering 3.0

[lr3guyjoe]

I have a 3.0 that I’m ready to sink.

Here is where I’m at. New plugs, wires, cap, rotor. New carburetor from national carburetors. New fuel filters, the big spin on one and the little one in the bottom of the fuel pump. New drive unit water pump. Timing has been set by the book.

On my last out the boat ran great for 20 miles at 75% wot. Stopped for lunch and for about an hour and then on the way back the boat started but didn’t want to come of idle and would stall and was real hard to get started again. Once finally got it going and back up plane it started running like garbage. Was struggling to maintain speed and the started pinging/knocking and loosing power if I pulled power back it would be okay for a bit but then it started doing the same thing at the lower power setting. Then it started popping/backfiring out the carb. I finally got it back to a ramp that was only halfway back to the the one I put in at. The last mile was at idle limping it back any time I tried to give it power it would cough and sputter. The whole time the temp never got above 170.

One of my passengers was sitting on the engine cover on the way down and back and he said it seemed to be warmer on the trip back than it had been on the way down. I’m thinking maybe the there is a coolant blockage in the head and there is a hot spot? I’m going to pick up an ir camera from a buddy and see if that shows any thing.

Any suggestions or ideas before I scuttle this thing?

 

[mbaker812]

I have a 3.0 that I’m ready to sink.

Here is where I’m at. New plugs, wires, cap, rotor. New carburetor from national carburetors. New fuel filters, the big spin on one and the little one in the bottom of the fuel pump. New drive unit water pump. Timing has been set by the book.

On my last out the boat ran great for 20 miles at 75% wot. Stopped for lunch and for about an hour and then on the way back the boat started but didn’t want to come of idle and would stall and was real hard to get started again. Once finally got it going and back up plane it started running like garbage. Was struggling to maintain speed and the started pinging/knocking and loosing power if I pulled power back it would be okay for a bit but then it started doing the same thing at the lower power setting. Then it started popping/backfiring out the carb. I finally got it back to a ramp that was only halfway back to the the one I put in at. The last mile was at idle limping it back any time I tried to give it power it would cough and sputter. The whole time the temp never got above 170.

One of my passengers was sitting on the engine cover on the way down and back and he said it seemed to be warmer on the trip back than it had been on the way down. I’m thinking maybe the there is a coolant blockage in the head and there is a hot spot? I’m going to pick up an ir camera from a buddy and see if that shows any thing.

Any suggestions or ideas before I scuttle this thing?

sounds like your head gasket blew.

 

[Rick Stephens]

Compression test.

 

[Eric 3.7LX Alpha 1]

Were all of these parts replaced after this happened or before? I think the compression test is a good idea also... Have you tried to confirm the carb is getting fuel? Disconnecting the fuel line at the carb inlet and cranking it over into a container to confirm it's getting gas. Some tanks have an inline filter screen in the pick up in the gas tank.

 

[lr3guyjoe]

Finally got some time to get the boat in the garage. This was an issue before I added the new parts they were attempts to remedy it.

Compression test came back at 155/150/145/150. Oil level is good and looks good not a hint of water.

Attached is a photo of the plugs. Im guessing it was getting fuel when it was running like crap because of how rich the plugs look. If it was not getting fuel and leaning out for those last 5 miles at reduced power would the plugs still look this rich?

I have an IR camera now and was going to take it out just to see if that she’s some light but when I moved the shifter to get to the plugs the shift cable sheathing pulled out of the compression fitting. So one more thing to the list.

Thanks again for the insight/help.

 

[Scott Danforth]

sounds like timing is off

what year 3.0?

stating about the filter on the pump leads me to a late 80's. does it have points? if so, service them and set the dwell with a meter, then set timing.

 

[lr3guyjoe]

The boat is a 2001 I believe the the 3.0 is considered a ‘98 model year? It has the electronic type distributor. I’ve also swapped the ignition module in the bottom of distributor and the pickup coil.

I’ve set the timing per the book. “Disconnect the carb, jump the two wires on the distributor, set the rpm with an optical tach etc etc

 

[Scott06]

Is your choke opening. I had it where my choke would intermittently stick closed and foul the plugs like that

 

[Lou C]

My thought as well. Is the choke opening; if so check to see if the float is sticking or the needle valve isn’t sealing….
Reman carbs are only as good as the person who set it up. Those plugs are REALLY RICH!
Also unrelated issue but you may have a water leak 3/4 of those plugs are quite rusty

 

[nola mike]

My thought as well. Is the choke opening; if so check to see if the float is sticking or the needle valve isn’t sealing….
Reman carbs are only as good as the person who set it up. Those plugs are REALLY RICH!
Also unrelated issue but you may have a water leak 3/4 of those plugs are quite rusty

Just found an issue with my choke not opening all the way, dunno when it started but my flame arrester was sooty, boat had been running pretty well at the end of season but lost a few wot mph. Also my ngk plugs used to rust up like that. Switched to the rust resistant ac Delco. Have you looked down your carb at idle to see if it's dripping?

 

[Lou C]

One issue with electric chokes is that they really are an electric de-choke…they close by spring pressure & the electric heater keeps them open…but if the electric supply to the heater isn’t 100% reliable they can close…
Old fashioned manifold heated chokes open slower than electric but once they are open they stay open….exhaust heat doesn’t fail….

 

[lr3guyjoe]

I’ll check the choke but I didn’t figure it running rich would lead to the pinging/knocking and coughing.

 

[QBhoy]

I’ll check the choke but I didn’t figure it running rich would lead to the pinging/knocking and coughing.

It definitely could. Defo check the choke operation for sure. What plugs is that you have in her ? Worth checking, but should it not be Br6fs or similar?
Your issue may be as a result of poor ignition too.

 

[Lou C]

Even though the carb was a reman from National Carbs I think you might need to go through it (clean, and check all the settings & adjustments). Check to see if the needle valve holds pressure. With carb off the engine, drain the fuel out of it. Then turn it over and see if you can blow through the fuel inlet. If you can't blow through it, the needle/seat is good (holding pressure/sealing) if you can, there may be a piece of grit in the seat keeping it from closing, or the rubber tip may be damaged. This has to be able to seal against the pressure of the fuel pump, if not it will flood. You want to make sure that the float is adjusted to the right height and is not rubbing against the sides of the bowl. Also if the float absorbs gas, it will be too heavy and cause the same problem. The other things that can cause rich running besides these are the choke not staying open as we said or the air bleeds being clogged.

 

[tank1949]

Even though the carb was a reman from National Carbs I think you might need to go through it (clean, and check all the settings & adjustments). Check to see if the needle valve holds pressure. With carb off the engine, drain the fuel out of it. Then turn it over and see if you can blow through the fuel inlet. If you can't blow through it, the needle/seat is good (holding pressure/sealing) if you can, there may be a piece of grit in the seat keeping it from closing, or the rubber tip may be damaged. This has to be able to seal against the pressure of the fuel pump, if not it will flood. You want to make sure that the float is adjusted to the right height and is not rubbing against the sides of the bowl. Also if the float absorbs gas, it will be too heavy and cause the same problem. The other things that can cause rich running besides these are the choke not staying open as we said or the air bleeds being clogged.

If everything else is ok, then check fuel lines/filter, including one in fuel pickup tube.