Trouble starting when warm

[Dcisco88]

Hi there, new to this so please forgive if this is in the wrong location. I have a 1987 renell with the mercruiser 5.7l 4bbl quadrajet carburetor. My issue is starting once the engine is warm. Cold start no problem but after running for a few she will not start again if she sits for more than 30 minutes. The car guy in me says vapor lock or boiled fuel. I purchased a new edelbrock 1409 but have yet to install it. I did notice that the distributor seems to have an excessive amount of play however when I checked the manual it is within tolerance. Any help would be greatly appreciated as I have beat my head over this for 2 years now. I did take it too two different marine mechanics with no luck. They say it's fine. Take it out and same thing happens.

 

[kenny nunez]

There probably is nothing wrong with the Quadrajet, they are much better than the Edelbrock. Heat soak will be just as bad with the Edelbrock.
There is one thing that you can try, sometimes the by-pass circuit on the starter solenoid is not supplying 12volts while cranking and for some reason is worse when the engine is warm verses cold.
Next time when the engine is warm and not starting take a small jumper wire connect the + post on the coil to a live 12 + post on boost solenoid or the + post on the battery then try cranking the engine. If it works then of course disconnect the jumper. Try this at home with a volt meter connect it to the + terminal on the coil and have someone turn the key, there should be at least 12 volts present in cranking mode.
If the volt test shows that you are getting 12 volts when cranking you could try adding more vents to the engine cover or open it if the engine will be not running for a while to let the heat out. Needless to say the quality of todays gasoline can really cause some problems.

 

[Bondo]

Hi there, new to this so please forgive if this is in the wrong location. I have a 1987 renell with the mercruiser 5.7l 4bbl quadrajet carburetor. My issue is starting once the engine is warm. Cold start no problem but after running for a few she will not start again if she sits for more than 30 minutes. The car guy in me says vapor lock or boiled fuel. I purchased a new edelbrock 1409 but have yet to install it. I did notice that the distributor seems to have an excessive amount of play however when I checked the manual it is within tolerance. Any help would be greatly appreciated as I have beat my head over this for 2 years now. I did take it too two different marine mechanics with no luck. They say it's fine. Take it out and same thing happens.

Ayuh,...... Welcome Aboard,..... Boat motors run fairly cool, so there's better odds that the float bowels are leakin' into the intake, causin' a flooded condition,......

 

[kenny nunez]

I have to agree with Bondo about the Quadrajets, they do have a reputation for that but they are easy to seal up.
If you try to use a Edelbrock you will need an adapter plate that sometimes raises the carburetor where the flame arrestor may come in contact with the engine cover.

 

[tank1949]

Hi there, new to this so please forgive if this is in the wrong location. I have a 1987 renell with the mercruiser 5.7l 4bbl quadrajet carburetor. My issue is starting once the engine is warm. Cold start no problem but after running for a few she will not start again if she sits for more than 30 minutes. The car guy in me says vapor lock or boiled fuel. I purchased a new edelbrock 1409 but have yet to install it. I did notice that the distributor seems to have an excessive amount of play however when I checked the manual it is within tolerance. Any help would be greatly appreciated as I have beat my head over this for 2 years now. I did take it too two different marine mechanics with no luck. They say it's fine. Take it out and same thing happens.

Timing may be too advanced. Change mechanics or buy timing light and manual. Trust me.

 

[Dcisco88]

Timing may be too advanced. Change mechanics or buy timing light and manual. Trust me.

Hi thank you for your response. I have very limited options for boat mechanics where I live. I have timed (or checked time) several times and only had to adjust once (first time). If I remember correctly manual says 8 degrees retarded. Don't quote me though it has been over 6 months since I last looked.

 

[Dcisco88]

I have to agree with Bondo about the Quadrajets, they do have a reputation for that but they are easy to seal up.
If you try to use a Edelbrock you will need an adapter plate that sometimes raises the carburetor where the flame arrestor may come in contact with the engine cover.

Hi there thank you for your response. I rebuilt the carb last season and when removed found the two screws from the baseplate to the main body loose. Thought for sure that was it! Alas next time out same issue. I checked float level as well. I have edlebrock intake manifolds however does not seem as everyone thinks they are great carbs so am reconsidering. I was concerned about clearance with the engine cover as well.

 

[Dcisco88]

There probably is nothing wrong with the Quadrajet, they are much better than the Edelbrock. Heat soak will be just as bad with the Edelbrock.
There is one thing that you can try, sometimes the by-pass circuit on the starter solenoid is not supplying 12volts while cranking and for some reason is worse when the engine is warm verses cold.
Next time when the engine is warm and not starting take a small jumper wire connect the + post on the coil to a live 12 + post on boost solenoid or the + post on the battery then try cranking the engine. If it works then of course disconnect the jumper. Try this at home with a volt meter connect it to the + terminal on the coil and have someone turn the key, there should be at least 12 volts present in cranking mode.
If the volt test shows that you are getting 12 volts when cranking you could try adding more vents to the engine cover or open it if the engine will be not running for a while to let the heat out. Needless to say the quality of todays gasoline can really cause some problems.

Hi there thanks for the response. Today's gas sucks quite literally. I have a gas station in the area that sells non ethanol fuel at a premium price. I filled a nearly empty tank with that and changed fuel filters still the same issue. I did not mention this is only an issue that shows on the water. Have not been able to duplicate this on land. Not sure if it has to do with no load on the engine or if when in the water heat stays in the hull longer due to water acting as an insulator? The engine sits just below the waterline and the doghouse leaves little room for ventilation.

 

[Dcisco88]

Hi all I forgot to mention two possible key points. Shortly before this problem began I sucked up a plastic bag around the water ports on the drive and Ultimately overheated the engine. Upon inspection of the engine after I shut down and lifted the doghouse I noticed gas seeping around the shaft that holds the butterflies on the carb. This has never happened again that I have observed. The other thing is that this only happens on the water. I have been unable to make it happen on land when hooked to tge hose. My engine sits just below the water line with maybe the heads and intake above. The doghouse fits fairly close to the engine as well. I have tried leaving the blower on for half an hour plus before starting with no effect. Thank you for all of your input and advice!!

 

[tank1949]

Hi thank you for your response. I have very limited options for boat mechanics where I live. I have timed (or checked time) several times and only had to adjust once (first time). If I remember correctly manual says 8 degrees retarded. Don't quote me though it has been over 6 months since I last looked.

Hi thank you for your response. I have very limited options for boat mechanics where I live. I have timed (or checked time) several times and only had to adjust once (first time). If I remember correctly manual says 8 degrees retarded. Don't quote me though it has been over 6 months since I last looked.

Retarded???? Aim TL on marks while friend advanced throttle. If it advances correctly, then at least that part is OK. I suspect timing is your issue.

 

[redneck joe]

does it run ok when hot? Just a starting issue?

 

[Dcisco88]

does it run ok when hot? Just a starting issue?

Runs great once she starts. Just getting started that is a challenge.

 

[Dcisco88]

Retarded???? Aim TL on marks while friend advanced throttle. If it advances correctly, then at least that part is OK. I suspect timing is your issue.

Hi there like I said my memory could be flawed. It was before winter last time I looked at the manual. I have checked advance with the tl and everything works as it should.

 

[Dcisco88]

Last year I replaced cap/rotor as well as plugs/wires and the positive/negative battery cables on top of general maintenance. The exhaust bellows will not stay attached to the outdrive side and I briefly entertained the idea that may have something to do with it but regardless of the bellows being in place or not the water level would be the same correct? I'm adding as I remember things. My schedule at work is crazy and on top of that I'm selling my house so my brain is kinda scattered. I'm hoping to be able to try some of the suggestions next week once I am caught up on more pressing matters. Thank you all for your input, I truly appreciate it.

 

[Dcisco88]

One more thing I didn't specify my location, I live in the reno Tahoe area so if anyone knows of a mechanic worth their salt in that area I'm open to taking it in. I have exhausted the shops I know of and that Google knows of.

 

[tank1949]

Last year I replaced cap/rotor as well as plugs/wires and the positive/negative battery cables on top of general maintenance. The exhaust bellows will not stay attached to the outdrive side and I briefly entertained the idea that may have something to do with it but regardless of the bellows being in place or not the water level would be the same correct? I'm adding as I remember things. My schedule at work is crazy and on top of that I'm selling my house so my brain is kinda scattered. I'm hoping to be able to try some of the suggestions next week once I am caught up on more pressing matters. Thank you all for your input, I truly appreciate it.

If my exhaust tube doesn't stay in place. I will drill and tape a ss cap screw to act as a ridge, similar to a hose nipple. If I can add 2 to each side (top and bottom) the better off that I will be. I have a 90 degree drill but I still may not have room to access the transom side to drill. Poor ass MC design, for sure!

 

[boozer1966]

Overheating could have caused damage to heads. Have you checked compression?

 

[Dcisco88]

Overheating could have caused damage to heads. Have you checked compression?

Compression is good. I have entertained the idea of putting a long block in. Just haven't bit the bullet yet. Oil is clean and she doesn't burn any.

 

[Dcisco88]

If my exhaust tube doesn't stay in place. I will drill and tape a ss cap screw to act as a ridge, similar to a hose nipple. If I can add 2 to each side (top and bottom) the better off that I will be. I have a 90 degree drill but I still may not have room to access the transom side to drill. Poor ass MC design, for sure!

I will try that thank you