Dies when throttling up from idle after warm up/ 89 merc 3.7 2bbl

[ddrieck]

Check your fuel tank vent line to see if it's plugged up. I was having similar troubles with my 1985 Thompson Cutlass 170 I bought from my brother. Boat sat in his shed for a few years unused. Turns out my vent line was plugged solid with a mud dobber nest so the tank would build pressure and force fuel past the carb needle and seat flooding the engine.

 

[karayj]

It's back again . I run up the lake for 15 min and stop. Then we want to more closer to the island to re anchor and it worn start. You can hear it about to catch but let got of the key and nothing. If the more the throttle forward there allot of back firing with flames. So I can only do starts without throttle movement . At the ramp at 1st t it take about there cranks and she idles
I DON'T HAVE A WORKING CHOKE Flap is wide open by me "set that way"
Then after 15 tries keep cranking for 15 seconds and by some miracle and catches for 20 at a good idle 1200 RPMS as I feather the throttle ,then it dies. I wait 20 mins she idles I cannot throttle up of it will die. The I idle away for 3-4 min but I cannot idle up of it will die, then I slowly bump the throttle it almost dies but seems to catch to a higher RPM 1900. I stay there for 3-4 min and then finally I can go full throttle. So much work

 

[CaptnKingfisher]

It's back again . I run up the lake for 15 min and stop. Then we want to more closer to the island to re anchor and it worn start. You can hear it about to catch but let got of the key and nothing. If the more the throttle forward there allot of back firing with flames. So I can only do starts without throttle movement . At the ramp at 1st t it take about there cranks and she idles
I DON'T HAVE A WORKING CHOKE Flap is wide open by me "set that way"
Then after 15 tries keep cranking for 15 seconds and by some miracle and catches for 20 at a good idle 1200 RPMS as I feather the throttle ,then it dies. I wait 20 mins she idles I cannot throttle up of it will die. The I idle away for 3-4 min but I cannot idle up of it will die, then I slowly bump the throttle it almost dies but seems to catch to a higher RPM 1900. I stay there for 3-4 min and then finally I can go full throttle. So much work

Coil and condensor can have problems once hot. I would recommend when having the no start issue check spark with an adjustable spark tester. Verify you have strong spark (jumping 1/2" gap). You could also have a bad ground or perhaps your points or condensor wiring is grounding on the metal plate in the distributor intermittently or something like that.. if you have weak/no spark when you can't restart the engine then we can start hunting down the cause.

If it's not ignition circuit then I go back to what I originally said about idle mix. The fact that youre able to start it easily when cold with no choke tells me you're probably set too rich. Take out the plugs after running the engine and take some nice photos of center electrodes and let's see what color they are and if they're wet or not.

Hard to help without being there.. need to follow our suggestions methodically. Start by measuring spark strength when it won't start. You want bright strong spark 1/2" gap

 

[karayj]

Thank you D Drieck that is great idea and makes sense.
That should come out and easily cleaned with carb cleaner.

 

[karayj]

The vent was not clogged DAM! The coil has been replaced last year with condenser , I thought the same getting hot and failing. I think it is ignition related because it requires a cool off period. The backfiring tells me timing. II will change the point AGAIN each year WTF!!!!

 

[karayj]

I know this is like regular car engines but maybe I’m missing something here. Is it possible that during the warm-up period the timing is thrown off and that’s why it never really seems to catch and iuntil 20 minutes cool down. I think the thing we have to think about here is what is happening that after 20 minutes the engine starts acting up and won’t restart after sitting for For five minutes. Another scenario is that if I drive around the lake for about 25 or 30 minutes at a full throttle and then I decide to idle back in to the dock a few minutes into the ride at idle speed she just quits and dies on me. And then it’s impossible to restart unless I let it sit for 20 minutes. Again something happens when I get this engine very hot let it idle she dies or if I shut it off and go to restart it it won’t until you let it sit for 20 minutes

 

[nola mike]

I think it this was ignition related heat problems it would show up at speed, not just when trying to start

 

[karayj]

The one common thing is 20 min not restart after 5 min of being off . You then have to wait / I do remember in the past it did restart and i was shocked thinking is was fixed. This worked for a whiles and the back to to the 20 min game. Something is getting hot and failing and when I try to restart is seems to want to catch but it does not. Then there is the pop and backfiring through the carb if I keep the key turn and try for 30 seconds . Also side note when I restart it I can only idle for 5 min and then I can throttle up it I try too soon it bogs and dies. So FUEL ??? or fuel pressure? FYI NEW fuel pump last year and filters

 

[karayj]

I have changed the Coil but it seems it could be the main cause.../ Maybe I need to move it to a COOLER place on the engine? 5 feet way LOL

 

[karayj]

1989 Regal 3.7 470 It's back again . I run up the lake for 15 min and stop. Then if we want to more closer to the island to re anchor and it worn start. You can hear it about to catch but let got of the key and nothing. If the more the throttle forward there allot of back firing with flames. So I can only do starts without throttle movement . At the ramp at 1st start up (cold) take about 3 cranks and she idles fine. And I heard out with no issues or hesitations . Like I said before I run 15 min up the lake to my spot. If I decide to re anchor or move with in 5 min of stopping she will restart If I wait 8-10 after stopping it WILL NOT restart.

Then after 20 min of waiting and keep cranking for 15 seconds and by some miracle and catches for 20 seconds at a good idle 1200 RPMS as I feather the throttle ,then it dies. I wait 2 mins she idles I cannot throttle up or it will die.
The I idle away for 3-4 min but I cannot idle up of it will die, then I slowly bump the throttle until it almost dies, there is not change in speed for a few min but them I wait and then seems to slowly catch to a higher RPM to where is should be 1900 . I stay there for 3-4 min and then finally I can go full throttle. So much work.

Things changed >>> Ignition Coil/ Fuel pump/ fuel filter in carb and pump and filter in there /Plugs/ Points condenser cap rotor each season/rebuilt 2 carbs BOTH have the same issues.

The Head gasket was changed 2 years ago/ lifters are quite and gapped 2 years ago correctly .... Could it be that ??? It seems to be that 20 min of cooling aka resting helps.. after a restart you have to idle for awhile or it stalls.
There have been time 2 that at the end of the season I run it allot to burn fuel and after running 60% for about 30 min as I head in at a 40% she skips a few times and dies. Then I get a tow in rather than sit in the boat lane for 20 min anchored for a cool off .

I get back to the back to the dock and she starts up and idles fine. What is it that happens at 20 min . I have noticed that on the way in I vent then engine compartment a bit by pulling back the engine cover for create a 8 inch gap. VAPOR LOCK???? If it was vapor lock way is it that opening the engine cover fully for 5 min after a no restart does not help?
I do remember 2 years ago being able to tube for 45 mi with no issue but that boat got a chance to idle a bit between riders.
It just sucks that I'm commented to a location for 20 min each time I head out . What if there is an issues and I need to get off the lake or a storm comes in after shutting the boat off for 10 min

 

[nola mike]

Have you actually checked for spark and fuel when it quits on you?

 

[karayj]

Have you actually checked for spark and fuel when it quits on you?

I will but like I said it tries to start aka catch so there is spark.... I'm headed towards flooded ... it is getting fuel because it smells when trying to restart/ Also remember after 20 min when is start you have to ginger the throttle or it boogs and dies. That tells me too much fuel or ignition... Timing /coil/.. One thing I remember if I vent the engine compartment 5 min before stopping it will restart after 5 min... I may need to add 3 vert grills on the engine cover ....

 

[nola mike]

I will but like I said it tries to start aka catch so there is spark.... I'm headed towards flooded ... it is getting fuel because it smells when trying to restart/ Also remember after 20 min when is start you have to ginger the throttle or it boogs and dies. That tells me too much fuel or ignition... Timing /coil/.. One thing I remember if I vent the engine compartment 5 min before stopping it will restart after 5 min... I may need to add 3 vert grills on the engine cover ....

Might not be getting consistent spark. Certainly sounds flooded. Have you checked to make sure your choke isn't closed? Are you trying to clear it by starting it with the throttle wide open? Once it starts and is running rough, have you looked down the throat at idle to make sure you aren't dripping fuel?

 

[karayj]

Might not be getting consistent spark. Certainly sounds flooded. Have you checked to make sure your choke isn't closed? Are you trying to clear it by starting it with the throttle wide open? Once it starts and is running rough, have you looked down the throat at idle to make sure you aren't dripping fuel?

I found last week hat the float was set incorrectly so I corrected it . So I have a new update today drove the boat to the other end of the lake 20 minute ride. Shut the boat off waited a few minutes she restarted no problem did this three times. Then on the way home after sitting for three hours on the water started up the boat drove it for about five minutes and she stopped that’s OK started right up again seem to be all right so we continued it’s is here when will the general public no 10 o’clock tomorrow idol at 1500 RPMs morning.

All of a sudden at 2000 RPM cruising in about I don’t know 12 miles an hour she started to sputter and die and then the routine started. I was able to start it twice and run for about 30 seconds and then that was it wouldn’t even idle anymore. After a small towline rescue of 10 minutes I got to the dock she kind of started but wouldn’t stay running. The engine was extremely hot to the touch the thermostat with a new gauge read 140 the rise and valve the over was TOO HOT To touch for more than 5 seconds.....Not sure what that means. I think I have an over heat issue. Head gasket was changed 2 years ago. I tested the thermostat. Will an engine stop from an overheat even after the over heat kill system has been removed? WATER PUMP???????

I know that’s a bit low. Now I’m wondering what could it be, there was a massive stench of gas but that’s because I was trying to start it so many times I guess . But now I mean this boat is getting pretty shitty it’s getting to the point where I can only start it ride maybe 10 or 15 minutes shut it off sit for three hours turn it on and come back to the dark another words I can venture too far away from the dock. My money now is overheating .... The head gasket was changes 2 years ago the impeller this year,
I think the boat is getting too hot ..20 min is the limit . After that is sputter and shuts off and will not idle until it cools for 20 min...

 

[nola mike]

I found last week hat the float was set incorrectly so I corrected it . So I have a new update today drove the boat to the other end of the lake 20 minute ride. Shut the boat off waited a few minutes she restarted no problem did this three times. Then on the way home after sitting for three hours on the water started up the boat drove it for about five minutes and she stopped that’s OK started right up again seem to be all right so we continued it’s is here when will the general public no 10 o’clock tomorrow idol at 1500 RPMs morning.

All of a sudden at 2000 RPM cruising in about I don’t know 12 miles an hour she started to sputter and die and then the routine started. I was able to start it twice and run for about 30 seconds and then that was it wouldn’t even idle anymore. After a small towline rescue of 10 minutes I got to the dock she kind of started but wouldn’t stay running. The engine was extremely hot to the touch the thermostat with a new gauge read 140 the rise and valve the over was TOO HOT To touch for more than 5 seconds.....Not sure what that means. I think I have an over heat issue. Head gasket was changed 2 years ago. I tested the thermostat. Will an engine stop from an overheat even after the over heat kill system has been removed? WATER PUMP???????

I know that’s a bit low. Now I’m wondering what could it be, there was a massive stench of gas but that’s because I was trying to start it so many times I guess . But now I mean this boat is getting pretty shitty it’s getting to the point where I can only start it ride maybe 10 or 15 minutes shut it off sit for three hours turn it on and come back to the dark another words I can venture too far away from the dock. My money now is overheating .... The head gasket was changes 2 years ago the impeller this year,
I think the boat is getting too hot ..20 min is the limit . After that is sputter and shuts off and will not idle until it cools for 20 min...

Not sure why you're quoting my post when none of my questions were answered or suggestions followed, but get an ir gun and check your temperatures

 

[karayj]

I did Noal the engine restarts for a few seconds that means there is spark.
I adjusted the floats and air mixture.
Rear cover was open 8 inches and another flap giving great venting
All this and same symptoms .
I now think reading other post similar issues it can be a weak spark causing a close catch but no idle or idle for 2 seconds then off.
It may be the resistor wire going to the choke and too much draw off the ignition switch. I have noticed that when the RADIO is NOT on it was OK from what I vaguely remember , there may be something there. After 20 min the resistor wire or ignition switch gets too hot. That is why if I sit and wait 20 mins (cool off) it works again. I the past I would run for 10 min 80% speed at on end of the lake.

The I would head in 12 MPH and that was 20 ride at that speed. I would stall and died 10 in on the 12 mph ride in why? <<< because 10 at 80% and 10 min at 12% = 20 min = stall and die. On the past I would scratch my head saying why was today OK? that is because I started the boat after sitting 3 hours and went FULL speed end to end and it only too 15 min .
I need to remove the power of the radio and dept finder form the ignition switch and direct form the battery instead. I need to recheck a small red wire going from my battery to the rear compartment ( starter maybe). BAD Connection poor voltage ....

 

[karayj]

I found an old post same issue as mine I guess it common with no solution.

Engine loses power after 20 minutes

I've spent countless hours online and in the engine bay, and simply cannot solve this mystery on my own apparently. I have a 1980 Mercruiser 228 (Chev 305) in a 20' boat. It starts easily and runs smooth... For 20 minutes... Then, it loses power and will only run at idle up to approximately...

forums.iboats.com

 

[nola mike]

Just because it kinda sorta catches doesn't mean it has adequate/consistent spark

 

[karayj]

Just because it kinda sorta catches doesn't mean it has adequate/consistent spark

Nola should I add a constant 12 volt wire to the coil direct from the battery as a test

 

[karayj]

Did you check timing after changing dwell? When you move the points, the timing also changes.

Do you have a temp gauge to confirm your engine temp? You should, these 470/3.7 motors don't like to overheat.

What's your voltage while running, on the (+) side of the coil. It should not be 12 volts with points. There should be two wires on the (+) side of the coil. One off the starter solenoid that gives the coil full 12 volts when cranking the engine only to help start the engine, and a second wire which lowers voltage when running. If you have full 12 volts to a points coil that are suppose to be fed thru a resistance wire they can get hot after a while and cause problems with spark.

This may be it!!! How do I know the resistant wire color ?
I like this idea.. So after the boat starts I need to test the voltage off the + side at idle and make sure it is under 12 .... if it is not do I buy a resistant wire? Where?