'06 21v engine problems

[lowdrag]

Ok, I've got a new 21V with just over 30 hours on it. I've had an issue with the 325 hp injected motor from day one. When it runs it runs great, but at times it has starting issues. The starting problems only occur after we've been out running the boat for a while, boarding, running around etc. When we shut the engine off for a couple of minutes to change riders there is no problem getting it started. However, if we sit for an extended time, an hour or more, it won't start. It will usually start and idle rough for 10 or 15 seconds and then die. After that, it just cranks and makes no attempt to start. The only thing that seems to work is to open the engine compartment, turn the blower on, and let it cool down. Usually after 15-30 minutes it starts and runs great.

I've checked for spark when it won't start and it seems to be fine. The ignition module has been swapped out but that did no good. My dealer has been great to me trying to figure this out but he's stumped a little as well. Every time I've had it there he has trouble reproducing the problem. However, when I'm out I'm pretty much assured this will happen if it sets for too long with a hot motor.

We both agree that it sounds like classic vapor lock symptoms but neither of us have heard of anyone else with an '06 having this issue. One time that he did have it, he said that the throttle position sensor had put out some trouble codes that he cleared with the computer. The last time I had this happen, I thought of that while trying to get it started. I unplugged the sensor that is hooked up to the throttle cables (it's called something similar to the throttle position sensor, but that's not it exactly). With the sensor unplugged, it started and ran fine. However, you then need to shut the motor off and plug the sensor back in in order to run the motor at anything above idle. I'm not sure that this was anything more than coincidence and that it wouldn't have started on its own without doing this.

The last time I had the boat out, I had mounted a fuel pressure gauge on the fuel rail to check for vapor lock. In order to do this you need to leave the big plastic shroud on top of the motor off. Under similar circumstances the boat started, idled a little rough for about 10 seconds and then ran fine. I'm thinking at the moment that it could be vapor lock that is compounded by the plastic shroud on the motor acting as a big heat retention/reflection device. Maybe the shroud keeps more heat trapped around the fuel rails causing the fuel to vaporize? I'm also guessing that when the dealer tried to reproduce the situation, he had also taken the shroud off prior to running the motor which is probably why he could get it to happen for him.

Anybody have any similar problems? Any suggestions, thoughts, or ideas would be greatly appreciated as this problem is really bothering me and is cutting into my enjoyment of what is an otherwise great boat. Brian, any thoughts?

I have had the same problems with my 05" 21V. It is a simple problem with no easy fix. Todays fuels are blended to lower emmisions, in our area they use ethanol up to 10% which will cause this vapor lock condition. To avoid this on hot days and with the boat under heavy load I just run the blower while we switch out boarders. If we want to stop for an hour I will run the blower and open the engine compartment for 5 minutes when we stop. So far I have not had any non start issues. In my survey to skiers I addressed this issue and suggested they go to a dual fuel pump design to help with this problem, but have not been contacted by any one from there.

[heydanniceshot]

Originally posted by Wake Snake


I have had the same problems with my 05" 21V. It is a simple problem with no easy fix. Todays fuels are blended to lower emmisions, in our area they use ethanol up to 10% which will cause this vapor lock condition. To avoid this on hot days and with the boat under heavy load I just run the blower while we switch out boarders. If we want to stop for an hour I will run the blower and open the engine compartment for 5 minutes when we stop. So far I have not had any non start issues. In my survey to skiers I addressed this issue and suggested they go to a dual fuel pump design to help with this problem, but have not been contacted by any one from there.

I do the same thing with mine. I just leave the blower on and it doesn't give me any trouble. Kind of annoying, but better than it not starting.

[1988comp]

If you are at any altitude at all, like over 2500ft, then your boat's ECM is simply set up too rich.

Getting fresh air to the intake is one way to make it less rich, but that is no long term solution. What you think is a vapor lock is actually the engine flooding with fuel.

If it is a new engine and not running right, take it back to the dealer. If it is off of warranty, get an ECM made to adjust, like from Holley or something.

[DKJBama92Mariah]

Altitide isnt a problem on EFI motors. They have a manifold absolute pressure (MAP) sensor. The ECU uses the MAP sensor in combination with the intake air temp sensor to calculate the appropriate air/fuel ratio. That's a massice oversimplification, but you get the point. Retrofitting an aftermarket ecu is just too big a can of worms; you're just asking for trouble. Not to mention its a brand new boat.

I'd see if you can find non-ethanol fuel and see if it improves. If so, it could very well be vapor lock.

What was your fuel pressure by the way. Typically the fuel pressure in the rails of a multiport EFI system is high enough so vapor lock isnt a problem.

[lowdrag]

I'm running in the flatlands of the midwest, so altitude wouldn't have much to do with it. Fuel pressure is normal when I key it up and the pump spins up it's running around 58 to 60 psi. I've had the boat back to the dealer twice and they can't get it to replicate the problem, so getting a boat fixed that runs fine is kind of difficult. The only other thing that I think it could be is the sensor on the throttle cable that relays the throttle position to the motor. I'm wondering if the heat is somehow causing it to send bad signals to the engine and not give it the proper amount of fuel for startup.

I run at 4700 ft at one lake and 5500 ft at the other lake and have no problems on cooler days with no humidity. I have only seen the problem on hot and humid days. So with that assumption the tps or map sensor would not be the culprit.

[AusBill32]

I've got 93 hours on my 21v 2006 and not a lick of problem with the engine. The water temp is in the low 60s where I gon most the time. I was in some 89 degree water about 4 weeks ago and rode for about 4 hours with no problems. My old inboard/outboard use to deisel (run on and/or not start) a lot in warm water because of the vapors even with the blower running.

[lowdrag]

Well, I'm pretty positive now that the problem is vapor lock. I'm spending the week on vacation at Table Rock Lake. Air temp is 95-100 and the water is 80-82. I don't have to wait nearly as long now after shutting the motor off to have the starting problem. I even left the engine cover open and still had the starting problem. With the fuel pressure guage in place I noticed some real pressure problems when the engine starts running rough. The pressure fluctuates between 20-40 psi in sync with the motor. After the motor dies it drop down to 0-10 psi. I decided I'd try to use the pressure bleed off from the fuel pressure gauge to drain the vapor out of the line. When I drained it into a beer bottle I noticed that there was a lot of air and some foamy fuel coming out. After cycling the fuel pump a few times and draining as much air out as I can, I cycle the pump a couple more times and the pressure jumps back up to 60 psi. After that the boat starts and runs fine. Now that I think I know what the problem is, does anyone know what can be done to fix it. I don't know what can really be done to keep the engine compartment any cooler. On top of that, since nobody else is really having this problem I don't have any idea of what could be different about my boat that causes it.