Engine acts like it is vapor locking

[rpaxton]

The other day I took my boat out on a very hot day, 101 degrees to be exact. When I first started the engine it had a slight miss at lower RPM. The boat ran fine at higher RPMs for about 30 minutes. We stopped to float and swim for about 45 minutes. When we went to restart the motor, it would start blowing some black smoke at startup, but when you gave it gas it would die. This continued for 5 or 6 attempts, then we were finally able to keep it running and get it up to 3000 RPM by advancing the throttle very gently and smoothly. After this the boat ran fine. Even turned it off while retrieving the trailer, and it started normally.

Has anyone had anything similar to this and what was the cause????


The boat is a 2000 22i with a Mercruiser 5.7L fuel injected motor.

[ghollow]

How long has it been since you changed your fuel filter?
Since you have an electric fuel pump, I would be surprised if it was vapor locking. It sounds to me like maybe some bad fuel or water got into the injectors. You might want to try running some fuel injector cleaner through the engine. I run a tank of fuel with Chevron Techron through my boat at the beginning of each season. It seems to help. I do the same thing in my truck every time I change the oil.

[rpaxton]

ghollow,

The fuel filter was replaced last May, but I will definately change it out and put some fuel additives in the fuel. I have read some other threads were people are talking about the possibility of the ECM ($1200) going bad, or the need for a SECOND fuel pump that Mercruiser claims needs to be added on some boats.

Rodg

[davet]

I had the same problem with my 2001 20I. I ended up having to put the extra fuel pump on. Mercruiser sent me a kit that had everything that I needed to install. Running fine now.....

[NICKYPOO]

I've had this happen in my 2000 22i but not to the extreme you had it happen. I've found that running the blower for a good long time (at least 5 minutes) before startup seemed to solve it. I will also just open the cover up for a second on real hot days. Also, check all your vent hoses. Especially the ones up front. During my new stereo install over the winter I replaced both of them as they had managed to get fairly dried out and had a few small tears in them. Pretty understandable with were they are located and types of abuse they see. It is also possible for them to get pinched with something wedged up against them. With what is a sad excuse for fresh air to the motor in these boats, it's amazing to me that they even run at all. Internal combustion engines run on gas and air. Cut that air in half with a pinched intake hose and it would be pretty easy to starve that motor. Could also be a clogged flame arrestor. There's another sorry excuse for air flow (I'm guessing you have the Merc. 350 Mag). Those flame arrestors are so bad that you can't even get a K&N for them. The K&N's got so much air to the motor that they ran into a horrible lean condition that the ECU/injector package was not able to over come.

[rpaxton]

Davet,

Did Mercruiser send you the extra fuel pump at their expense or yours? I have read where this seems to be the fix.

NickyPoo,

I will definately check those forward air intakes. I think the last time I was in the compartment forward of the driver's seat I noticed that the hose there had come off of the outside air intake. At the time I did not think it was that important, but after your response I will fix it immediately!

Does anyone know of an aftermarket kit that would place the motor's air intake directly outside the engine compartment? It seems very inefficent to bring air into the engine compartment the way it is being done now.

[NICKYPOO]

Hey, whoa, take it easy! Don't be givin' my top secret plans away. I've actually got a plan for using two inline, waterproof blowers to basically inject fresh air into the bilge instead of just the one in motor box to suck it out. Anybody could do it. You could probably do it for around $100. I personally just haven't gotten to it yet.

[Tequilasun]

I have always just let my blower run while the boat it started (and a little before). I read somwhere that it is cheap insurance for things like temp build up.

[rpaxton]

I would be interested in seeing your design plan. If you get a chance forward it to me. I promise not to steal it and market it, unless you are looking for a partner.....

[ghollow]

When I crank my engine up for the first time of the day, I always open the engine hatch first. After it starts, I visually check around the engine for leaks, etc. This saves the time of having to run the blower for a while before you start the engine. I usually do this when I am in the boat alone or I make the kids sit up front while the hatch is open for safety reasons.

[rpaxton]

Yes, we do that as well. We actually run the motor while we are still on the trailer and check to make sure we dont have a water pump or something that is leaking water. I sometimes even run the RPM up a little to check the tranny, before backing off the trailer (hatch closed at that point)

[NICKYPOO]

I don't have anything drawn up per say. I just know what parts I need to buy and parts I need to make. If you look at it I'm sure you could figgure out where to mount a blower fan in-line with the intake hoses. Wire them both to a switch and BAM, Air Induction. Kind of.

[rpaxton]

INteresting! Will the onboard computer be able to handle the forced air? It would need to be able to control the mixture, and it sounds like Mercruiser's unit is lacking somewhat.

[dogbert]

Originally posted by NICKYPOO
Hey, whoa, take it easy! Don't be givin' my top secret plans away. I've actually got a plan for using two inline, waterproof blowers to basically inject fresh air into the bilge instead of just the one in motor box to suck it out. Anybody could do it. You could probably do it for around $100. I personally just haven't gotten to it yet.

Ram enough air in there and you'll need an inter-cooler

[rpaxton]

Now theres an idea. You could do it with lake water, would not be that hard.............Hummmmmm