Hot days... Vapor Lock? Suggestions?

F

fins1up

New Member
Jun 4, 2007
43
Grand Lake, OK
Boat Info
280 Sundancer
Engines
T 4.3 MPI Alpha 1's
Last weekend the temp was in the low 90's. We ran for 30+ miles most of the time at around 3200 RPM. Stopped a couple of times for a few minutes then off and running again. No problems. In fact the boat (280DA Sundancer T-4.3 MPI Alpha) is running great. We found a quiet cove and fired up the grill for dinner. At that time I turned on the gen (Kohler 5KW) along with the A/C. Nice dinner and nice evening. Got ready leave and neither engine would start. One time last summer same problem on a hot day. I felt confident a vapor lock situation was going on, so I opened the hatch, turned on the blower, made another drink and waited 25 minutes. Tried it again and both motors fired up immediately. We had a nice run back to the dock.
The boat is in the water full time and we use it year round. The local MarineMax guys have gone the booster fuel pump route, but also add that does not always fix the problem. I will start making sure I run the blower when at anchor (on hot days) with the A/C on.
Any thoughts, comments or other ideas of things I might try?
 
I have never had a problem after I install the vapor lock pump kits. And I have installed LOADS of them. The only problem is that they are almost $400 each for just the part
 
Never had a problem like this. but I have MPI engines, are yours EFI?
 
I was going to ask that same question
are they carbureted?
the ones with the Weber/Carter AFB had a bad habit of boiling the fuel out of the bowls after you shut them off
when you would go to restart them hot, there was no fuel in the carb at all and only lost and lots of cranking would finally make one light

this was one of those problems that "only our dealer had" even though it happened on every AFB equipped boat we sold (I was a tech at a sea ray dealer at the time)

Mercury actually sent a fuel engineer down to tX and I took her out and demonstrated the problem on several different boats
on a hot restart the bowl was empty

If you have these carbs let me know and I can show you how in improve the situation
 
I'd love to see a solution - I think I have mine solved but it's just now really warming up in my area. I have the Weber 9600 on one and a replacement Edelbrock 1409. I think the AFB is the 750cfm - does your solution apply to the 600cfm as well?
 
.....as I have posted numerous times, and I apologize, this was a recurrent problem on my '98 290 DA w/ T260 hp EFI 350s. Only when I ran the generator. Running the blowers was always a fix to exhaust heat from the ER.
 
geriksen said:
I was going to ask that same question
are they carbureted?
the ones with the Weber/Carter AFB had a bad habit of boiling the fuel out of the bowls after you shut them off
when you would go to restart them hot, there was no fuel in the carb at all and only lost and lots of cranking would finally make one light

this was one of those problems that "only our dealer had" even though it happened on every AFB equipped boat we sold (I was a tech at a sea ray dealer at the time)

Mercury actually sent a fuel engineer down to tX and I took her out and demonstrated the problem on several different boats
on a hot restart the bowl was empty

If you have these carbs let me know and I can show you how in improve the situation
Click to expand...

No carbs, it's multi-port fuel injection. I replaced the "water separating fuel filters" last night. When I looked in the bottom of the bucket where I dumped the fuel from the filters, I did see a couple of small drops of water. Not sure if that could cause it or not, but at least I'll know those have been changed.
 
Mine does the same thing! PITA!!!!!! Should this booster fuel pump be covered under Mercruiser warranty?
 
Anyone with the 5.0 engines have the same vapor lock problem? This has never happened on mine (so far..).
 
I've had the same problem on mine. After running all day with the genny going and the air temp in the 90's, the 4.3's just won't start. My dealer tech told me that in addition to keeping the blower going and opening the engine hatch I must "prime" the engines. I know that is not the right term for it so I will explain it. When you hit the switch for the engine at the panel you hear the electric fuel pump make a BZZZZ that lasts for a few seconds. Cycle each engine switch several times before you actually try to start the engines. It works!
 
BarryB said:
I've had the same problem on mine. After running all day with the genny going and the air temp in the 90's, the 4.3's just won't start. My dealer tech told me that in addition to keeping the blower going and opening the engine hatch I must "prime" the engines. I know that is not the right term for it so I will explain it. When you hit the switch for the engine at the panel you hear the electric fuel pump make a BZZZZ that lasts for a few seconds. Cycle each engine switch several times before you actually try to start the engines. It works!
Click to expand...

I do the same thing and it does work but they still seem to struggle to start.
 
srt8mag said:
I do the same thing and it does work but they still seem to struggle to start.
Click to expand...

Thanks for the advice. Seems I'm not the only one who has experienced the problem. I'll give the "priming" technique a shot next time the problem occurs. I'm also installing a digital thermometer with a sensor in the engine room. We'll see just how hot it gets down there when it's hot outside and everything is running.
 
fins1up said:
Thanks for the advice. Seems I'm not the only one who has experienced the problem. I'll give the "priming" technique a shot next time the problem occurs. I'm also installing a digital thermometer with a sensor in the engine room. We'll see just how hot it gets down there when it's hot outside and everything is running.
Click to expand...


I prime, hold down the crosover switch and add a bit of throttle.
Still, this is not "right" and there must be a fix.
 
gerryb said:
Anyone with the 5.0 engines have the same vapor lock problem? This has never happened on mine (so far..).
Click to expand...

I had the same problem. My local MM added a booster pump and it has seemed to fix the problem. Been out 8 times since the pump was added and have had no issues. My boat is within its 2 year MerCruiser warranty so MM added the booster pump at no charge.

MM explained to me that the hot Florida temps and the winter grade fuel were the culprit for my problems when they first appeared this past March.
 
I have a 2006 280 Sundancer with 4.3's and after no trouble for over 2 years, its now vapor locking. I have only 123 hours on the engines and the extended 6 year warranty to boot. Mercury marine has stated there is a problem with the engines and the tight engine room, but will not pick up the cost of installing the boost pumps that they want installed to solve the problem. This company sucks, I paid $130,000 for this boat and their warranty, but no help.
 
I'm glad this is being brought up as I have been experiencing this since new. Not sure it's an engine room heat related issue as I only have to run them for 5 minutes to go to the fuel dock and get the no start issue.

My cure is to advance the throttles in neutral when starting.
 
6 week update - We've had some hot weather over the past few weeks (100+ days) and the problem has not re-occurred. We have used the boat several times on those hot days.

The only "mechanical" change I've made was to replace the fuel filters and run the fuel tank down below 1/4 tank to help get rid of any "bad" gas I may have picked up. I installed a digital thermometer in the engine room to see how hot it gets when underway after running for a bit. I've seen the temp in the 115 - 120 degree range, but if I run the engine room blower as suggested in this thread, it drops to around 105. I'm not sure if the 10 -15 degree difference when running the blowers corrects the problem, but so far, so good. I should also add I've made sure the fuel I'm purchasing does not have any ethanol in it. I'm not for or against ethanol, I just want to boat to start when I crank it over. For now, it does.
 
I have a 2001 270 with a 7.4L EFI that had a similar problem this past June on Dale Hollow Lake TN. It was about 90 - Had the gen on along with the blowers. Ran 30 minutes at 3000 rpm - drop anchor for 30 minutes then ran again for another hour at 3000 rpm. arrived at our spot, idled for 10 minutes as we go the boat in the proper location and anchored out. Gen still on (i can't remember if i left the blowers on). two hours later my engine would not start. got towed in, tried starter fluid but the engine was really missing something (air or fuel). it made a sucking almost hollow sound as it was trying to start. continued getting towed for another hour. after a few drinks, started the engine up and it ran fine, no more issues that day or any other day since.

never had the problem before that day or after that day

the mechanic said it maybe vapor lock but with EFI it would be hard to believe. however, we still cannot explain it. This issue in the post sounds just like mine.

The Dog House
St. Louis, MO
 
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