2006 Optimax 200 with vapor lock, history?

[daleatskiworldorlando]

Hi all, I'm trying to get to the bottom of a vapor lock problem that is showing up on a new 2006 Mecury Optimax 200 HP Sport Jet.<br /><br />First it would really help if I knew if the outboard version of this power head has any history of vapor lock. If not then it must be some type of heat build up problem that only shows up on the Sport Jet.<br /><br />So is there anybody out there that has run into vapor lock on the outboard version of the Optimax?<br /><br />Thanks for any info, Dale

 

[Silvertip]

Re: 2006 Optimax 200 with vapor lock, history?

Are you certain its a vapor lock problem and how did you prove it?

 

[Capt Ken]

Re: 2006 Optimax 200 with vapor lock, history?

EFI systems don't vapor lock because of high pressure fuel systems. Plus the temp of the engine isn't hot enough to vaporize fuel in any of the fuel lines.<br />Have you had anyone plug a DDT into the system to see just what the computer says is wrong? You don't look cross eyed at these systems without a diagnostic system in hand.

 

[daleatskiworldorlando]

Re: 2006 Optimax 200 with vapor lock, history?

Hi Upinsmoke, Capt Ken and the group.<br /><br />From Upinsmoke "Are you certain its a vapor lock problem and how did you prove it?" <br /><br />No I'm not sure it is vapor lock but the symptoms match to the tee. The boat starts and runs fine for a half hour or so then if it is shut down for about half an hour it will restart then start to run rough and then die. If left to cool off it will run fine again.<br /><br />From Capt Ken "EFI systems don't vapor lock because of high pressure fuel systems. Plus the temp of the engine isn't hot enough to vaporize fuel in any of the fuel lines."<br /><br />I'm sorry but that has not been my experience with EFI. I have had many confirmed (with fuel pressure gauge) vapor lock problems on inboard engines. Not all of the fuel in a EFI system is under pressure. The inlet side of the fuel system is under slight vacuum. Also, on many systems the the fuel pressure regulator sends extra fuel back into the inlet side of the fuel pump (that or the fuel filter) and heat can build up. On some engines there are fuel coolers that use water to cool them. I have had some vapor lock caused by a leaking impeller that was letting hot water back flow from the hot engine block back into the fuel cooler and this turned it into a fuel heater DOH!<br /><br />The boat is not in my shop yet, just trying to find out if the Optimax has had a history of vapor lock. What I'm thinking is if the outboard has no history of vapor lock but the sport jet does then it must have something to do with heat build up in the engine compartment or it might have something to do with hot water back flowing into the fuel cooler due to the different cooling water routing used on the sport jet.<br /><br />When the boat does come in the first two things I want to do are stick a temp probe in the engine compartment and record how high the temp goes after running and stoping for a half hour and then <br /> I want to check the fuel pump and cooler with my hand to see if I can find any hot spots.<br /><br />Thanks, Dale

 

[WillyBWright]

Re: 2006 Optimax 200 with vapor lock, history?

I find that most of the EFI problems that come involve the battery. Either it's not big enough, or the charginhg system is on the blink. It has to be an extra heavy duty marine starting battery. Deep cycle and dual purpose batteries don't cut it. The connections have to be clean with tight fasteners. Finger-tight wingnuts ain't even close. There's a lot of electrical demand on the battery and if it's the least bit lacking, performance and starting problems become like a plague. Phantom fault codes, too.

 

[Capt Ken]

Re: 2006 Optimax 200 with vapor lock, history?

It appears you are not familiar with the Optimax system. The only only unpressurized fuel is the incoming line which is rubber from the fuel tank to the engine. If its getting hot enough in the engine compartment to vaporize the fuel in that hose, the engine is fried. But to answer your first question. Optimax engines don't have a history of vapor locking. I would first plug my DDT into the system to check fuel pressures and to see if a sensor is causing the problem. There is no way to diagnois an Optimax without the DDT and current card.

 

[daleatskiworldorlando]

Re: 2006 Optimax 200 with vapor lock, history?

Hi Capt Ken and the group,<br /><br />"It appears you are not familiar with the Optimax system." <br /><br />This is correct, I took my first close look at the fuel system yesterday. (The boat is a new line we just picked up and I have not gotten setup with Mecury yet), I did find a complex 3 stage fuel pump system that the best I could tell has no water cooling on the VST. I did see water hoses on the fuel rail. I also saw a small fuel filter on the suction side of the first fuel pump. It would seem to me it would not take much dust or junk from the new gas tank to stop up this little filter. <br /><br />I think my next move it to try and get a DDT or a snap shot box to hook up to the engine and monitor the fuel pressure (and other things) if the fuel pressure does drop after sitting hot for a while and restarting I will check the little filter and maybe run a vacuum test between the little filter and the first pump.<br /><br />I also want to see how hot the fuel rail and water hoses get after sitting a while after runing hard. Still think something might be getting hot and boiling the fuel. I will also check the VST and see if it is getting hot after sitting.<br /><br />Will post back the this list on what I find.<br /><br />Thanks, Dale

 

[Capt Ken]

Re: 2006 Optimax 200 with vapor lock, history?

You are correct in what you say but wouldn't you think the temp under an outboard's cowling would be alot hotter than in the more open space of a jetboat.<br />Heck, if you think the filter is a problem, pull it off and blow thru it, its just a regular Mercury inline filter and its on the pressure side of the first pump, not suction.<br />Easiest way to tell if its an ambiant temp problem would be to test run the boat but when you stop, raise the hatch and let the hot air escape.

 

[uaw9fan]

Re: 2006 Optimax 200 with vapor lock, history?

Dale, I don't believe the DDT will give you fuel pressure ratings.The computer does not control fuel pressure.There is a fuel pressure regulator,and a air pressure regulator.Both are checked on their schrader valves at their respective rails.The air pressure is regulated at 80 psi and the fuel pressure is regulated 10 psi above the air pressure. So when you check the air pressure you should see 80 and the fuel should be 90.If there is any problem in the air compressor the fuel pressure will drop at the same rate.<br />Anyway just a little insight to get you started

 

[daleatskiworldorlando]

Re: 2006 Optimax 200 with vapor lock, history?

Hi all, thanks for the help. You gave me some things to think about.<br /><br />Regarding the small fuel filter, here is a picture of what I see on the 2006 200 HP Optimax sport jet. The outboard does not have this? If not I can see this could be one of the difference between the sport jet and the outboard. I'm thinking if the filter is restricting the fuel flow just a little it could be part of the problem.<br />

<br /><br />The other big difference I have found is the way the cooling water is pumped into the engine. On the outboard there is a rubber impeller but the sport jet uses the water pressure from inside the main drive impeller. So at low speeds the water pressure can drop to a low level. What I'm thinking is the sport jet can get hotter then the outboard under idle and low speed operation and this may be the real cause of the vapor lock problem that I suspect. If I can confirm this I will report back to this list with what I find.<br /><br />Thanks, Dale