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

[karayj]

I have some new questions on my problem that I’m chasing. So I read that floats and should be at 3/8 I saw on a YouTube video that for the marine Rochester two barrel it should be one and 330 tI have some new questions on my problem that I’m chasing. So I read that floats and should be at 3/8 I saw on a YouTube video that for the marine Rochester two barrel it should be 1 3/32 and this is measured by picking up the airhorn letting the float drop down so it’s on an angle and you measure from the airhorn to the middle of the float. So you put the measuring L that comes with the kit to the bottom of the airhorn at your starting point and then you measure down until the middle of the float says 1 3/32 .

Now when I look up three eights this tells me I am way off or am I. Any tips would be great my other question is and I have a situation as you know above that it gets 20 minutes and then it shuts down and I’m wondering if things are just getting too hot. One post mention that I should be able to touch the riser 90° or the exhaust manifold I doubt that and if I cannot I have an overheating issue.

My thermostat is at 1:40 at all times whether I’m sitting or cruising but I did notice after a short eight minute ride the intake is very hot. The other thing is the exhaust elbows are very very hot the hoses are OK. I forgot to bring my heat detection gun today on the boat but what should I be looking at because I read somewhere 90° and there’s no way the stuff is at 90 it’s much harder to the touch

 

[Eric 3.7LX Alpha 1]

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?

The resistance wire is solid purple. The other wire on the (+) terminal on the coil should be Purple/Yellow, which should only give 12 volts to the coil (+) when the engine is cranking over, and should be dead with the key in the run position. A new resistance wire is Mercury/Quicksilver #94227A2. To test the two wires on the coil, remove them and don't let them touch any ground. Now, with a multi meter, test each wire independently while not connected to the coil, both while the starter is cranking the engine over, and then test each with the key in the (on) position.

 

[karayj]

Yea It was 5.36 volts...so it is working as it should. Another issue today was I went to replace my oil filter and it was empty NO WEIGHT and nothing drained out. The oil was golden brown yesterday and not stinks of gas....
Long story I will add to this..

 

[karayj]

So what an interesting day on the water today. We started up no problem ran into a spot very very close by in case we had issues it would be along fell and uh after I stopped the boat which was only about 4 minutes of running we threw anchor we drifted after about 10 minutes I started it back up again took a couple of attempts but once it did start we moved it forward about 50 yards and threw anchor.

What I don't like is when it's already warmed up it never really starts right up it takes like four or five attempts until she idles pretty annoying. So we moved to a new spot where there was no wind sat there for oh gosh three to four hours and I was touching the engine such as the rise or other things and they were super super hot but the engine was off. So four o'clock comes around time to start the boat up after about five or six attempts she started to idle on her own I mean I can Rev the engine but I prefer just to turn the key and see if she idles I had to rev it up a couple of times 4000 rpm brought it down to idle once put it in gear she ran for a couple seconds and died after back fire thew carb.. This continued to happen where I couldn't even get it to idle now what was funny is after flooring it and turning the key and cranking for like 25-30 seconds it would finally catch and start and I kept on revving it and it would kind of stay 3000 RPM's 2000 RPMS and it would react to my throttle back and forth very smooth and clean but the second I back to put it into gear it would die.

This happened about five or six times and I got sick of it and started to look for a towing so I tide up with a guy and it was funny 'cause he said why you having its running what's going on I said the second I put it into neutral to throw it into gear she dies well that's interesting he said. As he was towing me in I was able to start it but only if I floored it wide open throttle add if I kept it at 2000 RPM it would have ran like that all day by the way when I was doing this I touched the riser and the exhaust they were super cool I get it when it's running and you check and you're moving the riser and exhaust and everything else is cool to the touch 80 degrees 90 tops so that's OK.

I guess it's super hot only after you run it for a while and stop it builds up like an oven maybe that's normal. So back to my story as we got close to the doc and me revving it at 2000 RPMS I told the guy untie the boat cause I started to back off and sure enough she stayed running after me keeping it at a high idle for like 3 minutes and I was able to dock it on my own.
I don't understand what's happening to this boat I did notice in the mercruiser manual there is a write up about this exact problem so it is a famous mercruiser issue apparently. In the past my temperature does not get past 140 degrees just so you know. I'm going to try to send a picture of the manual page that actually talks about this scenario I guess it's a very very famous issue something to do with the filler cap as event. What I need advice is what strange is in the beginning of this whole trying to get it started scenario every time I would put it into like an idle or lower than 2000 it would kind of run a little bit rough and then you'd get a pop out of the carburetor and then it would die so I'm wondering timing issue? Points condenser cap all replaced fuel pump replaced timing and dwell where done last summer before the end of the season. Wonder why I have to WOT to get it started and. I miss the days that we could move serval times in the lake 1 turn of the key it would start and idle… Also when I uncover the boat 3 days sitting you can NOW smell gas more then before .I bought a carb kit and point. Should I remove the siphon valve?

 

[karayj]

OK maybe some good exciting news. So the only way I could start the boat as if I was wide open throttle on a regular start I noticed the flat for the child was complete you know almost closed as it should be. But I also noticed when I finally got the thing running as soon as I backed off and I lifted the flame arrestor I noticed the butterfly was flopping all over the place. I quickly ran over while it was still running and kept it wide-open and Shernoff smooth as a butterfly.
Then I undid the three screws and made sure that it stayed open instead as a test the boat starts up no problem every single time it’s the way it used to be. So basically we have a choke flap issue that needs to be addressed. Other than that I should be fine one concern I do have is the voltage on the coil is 5 V and the coil does get up to 120°.

 

[karayj]

So I ran the boat for 25 minutes I shut it off I waited 10 minutes it started right up I mean right on the dime. None of this holding the key for 20 seconds none of this five attempts like before and then it finally ran. And now I know why when I did get it started I had to tap the throttle forward but wait for it to kinda catch up and then once the boat started to move to where The throttle is set at it would start to accelerate and it was safe to go full throttle because of the choke flap.

Now I know why the boat ran for 20 minutes and then died because things started warming up and the choke started flopping around closing lack of air stall. You wait 20 minutes everything resets the boat runs fine until she gets hot the flat starts flopping and she stalls now I know why we were having backfire through the carburetor nowhere because the choke flap was not set properly and flopping around open clothes halfway closed.

The boat was starving for air but I didnt really see it all the time until I had someone else do the throttle for me. And result if this happens to you after 20 minutes and you stall set the choke so it stays open all the time

 

[karayj]

So I have a new problem today I've been great for the last five days and then out of nowhere for some reason after running it for a good I don't know 20 minute run sit around 15 minutes another 20 minute run sit around 25 minutes on the third run it basically started to sputter and then it died the bolt restarts no problem right away. Once I put it in gear it's OK if I drive at idle speed 1000 RPMS if I try to accelerate she sputters and dies right away if I put the boat in neutral and I Rev it or keep it at 2000 RPMS it stays there but for some reason when you put it in gear under some load it just dies anything more than idle speed what the heck is that a few times we were able to kick it up a little bit but it only lasted 20 seconds and it would die and again if I put the boat in neutral I can Rev it are accelerate back and forth sit there idling leave it at 3000 RPMS she doesn't die at all it's only under a load or in drive I should have tested it in reverse but I didn't have a chance

 

[karayj]

OK final update hopefully someone can help me on this. The boat is running really well now what I have learned is you have to have the throttle down about 25% turn the key she fires right up awesome.
The boat reacts to full throttle immediately no hesitation no bog at all. Explain this to me. There are some days that I can run this boat up and down the lake for 2530 minutes no problem at all then there’s another day where I can run it and five minutes into 70% throttle I never go more than that she starts to fart pop spit bog and shut off.
You can start her up no problem in neutral you can read the engine you can keep it at 2000 RPM or 3000 RPMs no problem when you put it into drive and you try to give it a little bit more gas and idle she’ll run for 20 seconds and fart and die then I start it back up and she idles fine I put it into drive the second I try to give anything over 1500 RPMs she dies I quickly put it back into neutral gear I can rabbit and keep it there a 2000 RPMs or 3000 RPMs or thousand RPMs and she’s fine for some reason under a load she’ll die.
Then I start idling home I do this for about five minutes I give it a little gas it’s good a little bit more gas still good a lot of gas still good for about six minutes and then it dies again. So I basically have to idle home . The magic question is why in neutral gear I can keep it at 1000 2000 or even 3000 RPM steady for an hour but the second I try to put it in drive under a load she doesn’t last more than five or eight minutes

 

[Eric 3.7LX Alpha 1]

So I just re read this thread from the beginning. You've been having problems for 2 years with this thing.

What did you do to fix your flopping choke plate issue?

Curious what brand and part number are you using for spark plugs? they are not all created equal. I don't think it's your problem just wondering...

Did you ever put in a fuel water separator? You previously removed the filter at the fuel pump, and was having problems with debris getting into the filter at the carb inlet. You put in an inline filter which was previously recommended to remove it they are not Coast Guard approved. It has to do with fire rating, and being able to withstand a fire for a certain period of time should you have one in the engine compartment. One of those plastic inline filters will melt instantly and just feed a fire with more fuel. Same goes with the rubber fuel hose in the boat. It is suppose to be Type A1 which also is fire rated.

Some gas tank pick up tubes have an inline screen/filter in them near the top. If you have one that is partially plugged up it could give you bogging problems.

It does sound like it's fuel/carb related. An engine bogging under load if you search it.. is fuel related, and the lack of it getting in the engine.

Have you ever tried running it off a separate gas container with clean fresh gas or checking your fuel pressure?

 

[Bondo]

The magic question is why in neutral gear I can keep it at 1000 2000 or even 3000 RPM steady for an hour but the second I try to put it in drive under a load she doesn’t last more than five or eight minutes

Ayuh,..... Because with no load, there's no demand for fuel flow,....

 

[karayj]

Ayuh,..... Because with no load, there's no demand for fuel flow,....

Ok so what do I do? New fuel pump is bad put back the old one? I only change it because I thought it was the original problem