HELP...3.7L motor runs fine for about 30 minutes then bogs out and dies????

[AKFISHRIPPER]

So the last 3 times I have taken my boat out it started fine and after about 30 minutes of driving around between 2000-3000 RPMs all of a sudden it bogs out and dies. When I try to restart it will turnover but not start unless I let it sit for a little and it will run again. After the first time it happened I siphoned the gas out, changed the fuel filter, drained the pump bowl, and drained the carb because I though it may have been water in the fuel, after that I backed it into the water (still on the trailer)and ran it for about 45 minutes at 1500 RPM with no issues but when I took it out the next day and drove it around it happened again....Also I put about 20 gallons of fresh gas along with the blue fuel treatment. I'm military and don't have a lot of cash to throw around at troubleshooting so any help would be awesome, thanks guys.

 

[Don S]

Re: HELP...3.7L motor runs fine for about 30 minutes then bogs out and dies????

Sounds a lot like a plugged up fuel vent. Try it again and remove the fill cap when it starts bogging and see if you hear air being sucked in around the cap as you remove it.

 

[Howard Sterndrive]

Re: HELP...3.7L motor runs fine for about 30 minutes then bogs out and dies????

worth reading too:
http://www.audibmw.info/pdf/Gasolineengine/5.pdf

you might try a run with the hatches open and blower on to cool the fuel system to see if the engine might be vapour locking.

 

[AKFISHRIPPER]

Re: HELP...3.7L motor runs fine for about 30 minutes then bogs out and dies????

Sounds a lot like a plugged up fuel vent. Try it again and remove the fill cap when it starts bogging and see if you hear air being sucked in around the cap as you remove it.

As a matter of fact I do remember taking the cap off one day after running the boat and it did suck a lot of air, I'll try that and hope it works...thanks.

 

[AKFISHRIPPER]

Re: HELP...3.7L motor runs fine for about 30 minutes then bogs out and dies????

worth reading too:
http://www.audibmw.info/pdf/Gasolineengine/5.pdf

you might try a run with the hatches open and blower on to cool the fuel system to see if the engine might be vapour locking.

I read that PDF and it has some good info thanks, also I looked over a few related post and a few guys say something in the ignition system may be failing when the engine gets to hot so I'll try the boat out tomorrow and test the ignition if the fuel vent thing doesn't work.

 

[Oldrod 47]

Re: HELP...3.7L motor runs fine for about 30 minutes then bogs out and dies????

Be suspicious of the coil, did a bunch of things on one, cap, plugs, plug wires, fuel pump, filters, ignored the obvious bright blue aftermarket coil, hey- its been replaced. Only thing left so replaced and no problems for 3 years now. Coils breakdown from heat and you have 1/2 hour of heat underload - and they are relatively cheap. The other component that could fail is the condenser if you are running a points distributor.

 

[AKFISHRIPPER]

Re: HELP...3.7L motor runs fine for about 30 minutes then bogs out and dies????

So I took the boat out Friday and the samething happened after about 20 minutes of motoring around. I opened the filler cap and no air sucked in, I changed the fuel filter and checked all the lines again but nothing changed. I guess its time to take it into the pro's. Any recomendations on a good repair shop?

 

[Don S]

Re: HELP...3.7L motor runs fine for about 30 minutes then bogs out and dies????

When the engine dies, have you checked for spark just after it dies?

Also remove the flame arrestor, and operate the throttle and see if you get fuel from the accelerator pump.
http://forums.iboats.com/showthread.php?t=167561

Tough recommending a shop when we have no clue where you are located.

 

[AKFISHRIPPER]

Re: HELP...3.7L motor runs fine for about 30 minutes then bogs out and dies????

I haven't checked it for spark, but it still sounds like its turning over when I crank it. I'm located in Kittery Maine, by the way.

 

[fiberformak]

Re: HELP...3.7L motor runs fine for about 30 minutes then bogs out and dies????

my 470 merc has points and when they need adjusted or need replaced thats how they have acted for me. they get hot and dont work then. then after cool down work fine for a bit. that just my two cents.

 

[a1nowell]

Re: HELP...3.7L motor runs fine for about 30 minutes then bogs out and dies????

AKF,
I'm with Oldrod, sounds like the coil.

In early April I was out for the first time this spring and after about 20-25 minutes of running just fine, my 470 started to run like crap. Nursed it back to the dock checked everything over, all good (new plugs & wires the previous week, Petronics ignition). The gine cooled down, fired right up and I went out again, in 20-25 minutes it started to miss something terrible. A friend suggested the coil, I went to NAPA and got a $14.00 universal 12v coil and installed it. Problem solved. I have probably been out 6-8 times since then, runs like a top.

Just my $0.02 worth,

Larry

 

[AKFISHRIPPER]

Re: HELP...3.7L motor runs fine for about 30 minutes then bogs out and dies????

my 470 merc has points and when they need adjusted or need replaced thats how they have acted for me. they get hot and dont work then. then after cool down work fine for a bit. that just my two cents.

Yea I'm just going to replace the points and coil today along with a complete tune up to rule out the ignition system.

 

[a1nowell]

Re: HELP...3.7L motor runs fine for about 30 minutes then bogs out and dies????

AKF,
Be sure and let us know the results!

Larry

 

[AKFISHRIPPER]

Re: HELP...3.7L motor runs fine for about 30 minutes then bogs out and dies????

AKF,
Be sure and let us know the results!

Larry

Well I put a new cap, rotor, pionts, condenser, plugs, and fuel filter in yesterday. When I started the motor it was running like crap so I adjusted the distributor and it purs like a kitten now. I'm still not 100% sure what was bad but the rotor and disrtibutor cap looked burnt, also the plugs were really dry and black. I'm waiting on the spark plug wires to come in today so I can put those in after work and test it out on the river.

 

[mjfink]

Re: HELP...3.7L motor runs fine for about 30 minutes then bogs out and dies????

For what it's worth, I had a very similar problem with my 2005 5.7 TKS motor. Would run great, but then, after 30-1hr of running (didn't seem to matter if it was fast or not) it would bog and die out (sounded like it just wasn't getting enough fuel). After some digging, it turned out the coil was failing when it heated up. I thought I had water in the gas and was changing the fuel filter after it died (which seemed to fix the problem). What I was actually doing was giving the coil enough time to cool down.

Changed coil, problem solved.

 

[AKFISHRIPPER]

Re: HELP...3.7L motor runs fine for about 30 minutes then bogs out and dies????

So I took the boat out yesterday and it had a little valve chatter so I adjusted the distributor and it ran great....then after about 2 hours of trolling around we decided to open her up to 3000 RPM in rough water for about 10 minutes and the same issue happened again. I brought a new coil with me so I replaced it on the water and ran it for another 30 minutes at lower RPM with no problems. I'm really starting to think it’s something fuel related because the issue doesn’t happen until higher RPM in rough water, maybe the floats are sticking or there’s some debris in the carb?

 

[bwthor]

Re: HELP...3.7L motor runs fine for about 30 minutes then bogs out and dies????

So I took the boat out yesterday and it had a little valve chatter so I adjusted the distributor and it ran great....

I don't see how adjusting the distributor would fix valve chatter. Are you adjusting your distributor by turning it? If so, I'm betting that the chatter you are hearing is a result of having your ignition timing advanced too far causing pinging. This happens because your air fuel charge is being ignited before the piston is past top dead center, causing the pinging noises. This is very hard on an engine. You may also notice your starter not being able to turn the engine over smoothly.

You need to set your timing using the proper tools!

 

[AKFISHRIPPER]

Re: HELP...3.7L motor runs fine for about 30 minutes then bogs out and dies????

Yea the starter was having a hard time turning the motor over but after we adjusted it ran and started great. I'm going to trar the carb apart today and see if thats the issue, if thats not it I have no idea.

 

[AKFISHRIPPER]

Re: HELP...3.7L motor runs fine for about 30 minutes then bogs out and dies????

I rebuilt the car per the instruction manual and ran it with water ears in my driveway and it ran good. I put it in the water and it started right up then I turned it off for 5 minutes and it wouldn't start so I took the top of the carb off and the accelerator pump rubber seal was all torn up....AAHHHHHHHHHHHHH This thing is driving ne nuts, I bought another accelerator pump and it should be her tomorrow so hopefully I'll be able to test it AGAIN on Saturday.

 

[Don S]

Re: HELP...3.7L motor runs fine for about 30 minutes then bogs out and dies????

When you changed the points, did you set the points using a dwell meter, THEN set the timing with a timing light? or are you doing all this by ear?