2000 20i strange problem

[lammbn]

I'm having a strange problem with my 2000 20i. it has a CARBURATED 5.7 mercrusier in it. at the first of the day it starts and drives like a dream until we park it for a bit. after it sits for more than 30 minutes or so and cools down it starts right up and goes for about 30 seconds to a minute and then it stops. i can be at any throttle setting and it acts just like i pulled the throttle back to idle. the transmission disengages and the engine goes back to idle. it does not die completely. if i pull the throttle back to idle and then forward again it re-engages and throttles up. sometimes it only does this once and then runs great again until we let it sit for an extended period of time. other times it does this several times before its good again. never more than a couple minutes or so of dealing with this though. what could be causing this? does the linkage have a safety disengagement mechanism or something? i know its not just the transmission slipping because the engine doesn't rev up. just goes back to idle. i'm stumped. its not a huge problem because it fixes itself quickly but i don't want to wait to see if it gets worse or quits working altogether.

[Ruger761]

Sounds like vapor locking to me, which is pretty typical of these year boats especially with a carb. So its nothing to get too worried about. But can get worse as the summer heats up. Mine is EFI and it completly dies due to lack of fuel pressure but brothers 2001 is carb and it will stay at an idle most of the time. The best way some have found to fix the problem is adding a secondary fuel pump (lift pump) before the fuel separator. Ive attached Merc service bulliten which goes into more details. This winter I added a pump back by the tank and so far, no vapor locking. Last summer did it every time we took it out.

service bulliten.pdf

[Ruger761]

Oh forgot to ask, did you change fuel separator this spring?

[lammbn]

ok. thanks for the information guys! i just bought the boat in April so i do not know if that fuel separator was changed out. seems like i may have to do that. glad its nothing that is a unique problem

[Ruger761]

Also if you just boought it and dont know if the impeller has been changed out, I would highly reccomend you doing it. Easy to do and only about $25-30 which sure beat a tow in and ruining a trip to the lake

[lammbn]

yeah, i made the shop change the impeller and rebuild the carb before i bought it. runs like a top other than this. love this boat. now time to dump some money into a few luxury items such as a custom bimini top and perfect pass

[Ruger761]

Oh by the way we require some pics :P

[Joeprunc]

I'd put money on it being bad gas. Have you burnt through a tank yet? Is it still happening with freshly pumped gas (not from a marina)?

I'd see if you can pull out that gas, or if you only have a few gallons left top off with some fresh gas. As recommended replace the fuel/water separator, I usually replace mine after burning the first tank of gas after winter.

[M&M]

2000 20CI, Missouri Ozarks. I agree with Mr. Allen. My fuel injected Merc. vapor locked when I used it the first year. I tried lots of things. Then I checked my blower. It ran but the fan blades were gone! I installed a new Holland blower and use it while parked and have not had the problem. One time I poured a beer can full of lake water on the transmission, fuel cooler and the boat started right up and ran. M&MFamily Lake Pic August 2012.jpg

[lammbn]

I've already burned through about 5 tanks of gas this year we are kinda diehards lol. I am taking it out again tomorrow and if we stop long enough i will see if running the blower helps. i will also probably try opening the engine cover to let some hot air out every so often while stopped. funny thing is the first two tanks of gas this never happened. guess we will see if i can prevent it now that i know what the problem is. thanks again guys!

[boatwakes]

Sorry guys, I disagree with all the above suggestions, you're looking at a throttle/mounted shifter problem. The linkage behind the shifter/throttle mechanism is disengaging and the throttle spring and shifter cable are falling back to idle/neutral position. Then re-engaging and shifting in and out of gear gets the cable pivot points back into position and it goes again. Pull the shifter assembly off the wall and look behind it that both the cable pivot points are anchored and that the mechanism itself doesn't have any damage or missing parts.

[thegreatwhay]

Guys.. I seem to have read so many posts about vapor locking. I am a bit confused about this because why is it that this is all of the sudden this is the answer for boats that have run like champs for a while? I understand the ethanol issue, but what does not make sense for me, is that this all of the sudden started at the end of last year for me.
I replaced the water fuel separator, then the impeller, figuring it was right beside the fp so "just to be sure". Then cap and rotor. While all of these things needed to be done anyway, no success. I bought a fresh tank of gas, but from the marina. Supposedly "treated". So here i sit on the back porch, aggravated because i cannot figure this out.
Talked with a buddy of mine, and we discussed the oil pressure sensor... No fix there...
Has anyone had an issue with something in the tank blocking the flow of fuel?
Essentially my problem is the same. I can idle along fine. Boat restarts with no issues... But when accelerating or getting above 2000 rpm, i have nothing. I back off the throttle, and it recovers..
Anyone have more details on the possible culprit? Could it still be bad gas?

2003 Tige 22V. I have owned the boat its entire career, and live in the Atl, GA area.
Thanks everyone for all of your help.

[boatwakes]

If all you're lacking is power above 2000 rpm go to the ANTI-SIPHON valve located at the top of the fuel tank pick up tube. Replace with an NPT to barb brass fitting (full flow) and test run. If it solves the problem, replace with a NEW aluminum anti-siphon valve from a marine store as running with a full flow non anti-siphon isn't safe.

[Ruger761]

Sorry guys, I disagree with all the above suggestions, you're looking at a throttle/mounted shifter problem. The linkage behind the shifter/throttle mechanism is disengaging and the throttle spring and shifter cable are falling back to idle/neutral position. Then re-engaging and shifting in and out of gear gets the cable pivot points back into position and it goes again. Pull the shifter assembly off the wall and look behind it that both the cable pivot points are anchored and that the mechanism itself doesn't have any damage or missing parts.

Everyone can have their own opinions of whats going on, but when a boat runs fine and then it only does this after sitting for 30 min to 1hr typically points to vapor locking/fuel issue not a shifter issue. A shifter issue would do it no matter how long the boat sat and would even do it on the very first start up and run.

A bad anit-siphon valve can cause vapor locking symptoms when its just a bad valve blocking full fuel flow. No more than they cost if you have a marine store close, Id just replace it with a new one once you try the brass barb full flow testing.

[boatwakes]

Thegreatwhay, are your symptoms of fuel starvation/sluggish engine above 2000rpm instantaneous or after a few seconds of running at those rpm? I agree with TeamAllen that your fuel pressure needs to be monitored during the acceleration and above 2000rpm but we also need to know which motor you're dealing with. I'm assuming Mercruiser so you're fuel pressure should be at 30psi+-2psi at all times. If it deviates lower, try the above mentioned anti-siphon valve resolution, fuel filter replacement or running a small gas can with an unobstructed fuel line picking up from it. If higher, your fuel pressure regulator is at fault. You can purchase the fuel pressure test gauge at any auto parts store, just be sure you get the unit for EFI systems, they usually run about $40 and can test pressure up to 100psi. Unfortunately, there are many symptoms that can present for individual engines and sometimes information gets lost in translation. Do your best to give us as much information and the scenario surrounding your symptoms and when they started so that we can give you the best treatment without too much fodder. Hopefully both of you guys can get your separate issues resolved before too long and get back out on the water. Keep us posted!!!