boat runs on the trailer but shuts down in the water

[Bilotto11301]

My boat runs fine at the house on the trailer, it starts up everytime.. However, when I launch it, it will run for about 20mins and shut off and wont fire. It wont fire back up again until I take it out of the water, it will start right back up.. Its a 1986 Supra TS6M someone please help.. Recentley replaced distributor and coil and new spark plugs.. ANY ideas at all.. This is very sad and depressing, last four times I have been stranded on the water trying to figure out what it is.. PLS HELP...

-Vinnie Valentino Bilotto Tallahassee,FL

[wotan2525]

My boat runs fine at the house on the trailer, it starts up everytime.. However, when I launch it, it will run for about 20mins and shut off and wont fire. It wont fire back up again until I take it out of the water, it will start right back up.. Its a 1986 Supra TS6M someone please help.. Recentley replaced distributor and coil and new spark plugs.. ANY ideas at all.. This is very sad and depressing, last four times I have been stranded on the water trying to figure out what it is.. PLS HELP...

-Vinnie Valentino Bilotto Tallahassee,FL

How frustrating!! When you run it on the trailer do you have the engine cover off?

[Bilotto11301]

Yes its always open when I run it at the house, but closed on the water.. However it fired up with the cover closed when I took it out the water yesterday. The temperature gauge never gets hot at all...

[csuggs]

Interesting. How do you have the water hooked up when on the trailer? Step, by step, what are you doing when you run it on the trailer? When it quits in the water, you said it takes about 20 minutes. Have you run it for 20 minutes on the trailer, or just short times? I can't believe this has anything to do with the boat being in the water unless you're getting water in your bilge and shorting out the wiring.

[Bilotto11301]

I have ran it for over an hour on the trailer in my yard w/ the water hoooked up to the motor... turned it on and off w/ no problem.. but i havent ran it on the water with the motor cover off or open.. its always closed...

I hook the water up thru the back of the motor where that water supply hose mounts to the engine.. i hold it there and let the water flow that little metal canister w/ the little tiny holes it in.. its the same place i clean the grass out when it clogs ups.. it fires up everytime no problem.. it idols a bit rough, we had some timing issues w/ the distrbutor but we got it all right.. i put a new coil on it yesterday, but i havent taken it out to find out if im goin to break down again or not.. no matter what i do i cant get it to break down on the trailer.. i cant closer the motor cover with the water hooked up tho..

[csuggs]

If the only difference between on the trailer and in the water is the motor cover being on, then it sounds like a heating issue. I've heard of some problems where the heat buildup can cause the gas to vaporize. Is this your first season with the boat?

[Bilotto11301]

No I had it all last season and it ran perfect... IT cut off on me a few weeks ago and we had to replace the whole distributor and its components.. we got from carquest.. it is possible for the coil to overheat?

[Bilotto11301]

the temperature guage never gets barely above normal...the boat wouldnt start after it broke down and soon as i took it out the water tens mins later on ther trailer.. it fired back up.. W/ THE COVER ON

[suprava10]

I have seen this in jet skis and outboards but never an engine cover. This symptom perfectly describes an exhaust leak. The exhaust chokes out all of the oxygen and the engine won't run. Try this to see if this is the problem: Start the boat up at the dock with the engine cover on and try to run it. As soon as it starts to die quickly open the engine hatch and see if it starts to run better, if it does than that is your problem.

Also, does this problem occur when the boat is in gear or just idling. Under load can cause completely different problems than on the land!

Chris

[Bilotto11301]

I def open the cover and try to start it when it breaks down.. you think I should take the cover off comepletely and take the boat out and see if the problem occurs? someone told me the gas could be boiling and the engine could be vapor locking...

its almost like its not breathing right.. and when the it comes out of the water then it can breathe better... are my mufflers filling up with water or something? i got those silver drums in the back for my exhaust... no flaps

[mapleleaf]

fuel delivery??????

[suprava10]

It could be extensive back pressure. Have you cleaned the traps out recently? I would run it with the cover off and see what happens it could alleviate/dictate what is going on.

[Bilotto11301]

Last night I ran it got it hot on the trailer and soon as the mufflers got under water it would start.. Then when I took it out of the water, it fired up instantly once it blew the water out the exhaust..

Does anybody know anything about the exhaust I have.. They are the silver circular drums with little plates that stack against the boat.. I can see where there is clear caulk around them form where someone else maybe had a problem sealing them before or maybe leaking... Is it possible they are taking on to much water and when it fills up its shutting down and not allowing it to start back up...?

[Mani]

If I'm not mistaken they're called Supra traps.

[Bilotto11301]

I meant to say "AS SOON AS THE MUFFLERS GOT UNDER WATER IT WOUDL'NT** START... sorry guys

[Bilotto11301]

How do I clean the "traps" ?? I took the left side one off and it didnt seem to have anything wrong with it other than some black smut.. It may not be sealed so great, it had glue and caulk around the base of it though...

[Matt Laird]

On a little different note, Does your boat sit @ the same angle on the trailer as it does floating? Sounds like maybe you have an issue with the fuel, Maybe trash in the tank & when you trailer it it shifts the fuel & trash @ the ramp... Hopefully you have it figured out with the exhaust...

[wotan2525]

I'm stumped -- I can't imagine that water in your exhaust would have any effect at all on your engine. There should be plenty of back-pressure to push out this water (that's how it was designed.)

The super-trapps are pretty simple and I can't imagine any possible way that they would get plugged or clogged up. I personally think your engine is either vapor locking from the heat or choking itself out from not having enough oxygen under the dog-house. I'd investigate this by trying to run it with the cover off on the water -- although maybe you already tried this and it killed as soon as you backed it into the water? How are you attaching a hose when you run it on land -- with a plunger setup or with a plumbed in hose?

[Bilotto11301]

It takes two peoplel to run it with water on the trailer, I dont have any special adapter or anything.. we just unhook the waterhose on the motor and hold the garden hose up over the little water filte that is on the back of the motor..

the boat sits a the same angle on water and on the trailer..

I am going to seal the heck out of the traps in the back, it looks like someone did this before and it could be weathered and wearing off and possibly letting to much water in...

I will run it with the motor cover off and let you guys know what happens this weekend...

[Sid Deville]

I had an issue when using water from the tap is pressurized and the watter is pushed into the engine, when off the hose, the engine hoses collapsed (cuz now the engine has to suck the water). something to consider. I replaced the engine hoses and it did the trick.

[19astewart81]

Did you figure this out? I am having same issue but I was told to change riser gaskets and make sure clean fuel delivery. I ordered riser gaskets and cap rotor and fuel filter. I cleaned tank and fuel system. Wish me luck.

[19astewart81]

I'm stumped -- I can't imagine that water in your exhaust would have any effect at all on your engine. There should be plenty of back-pressure to push out this water (that's how it was designed.)

T
he super-trapps are pretty simple and I can't imagine any possible way that they would get plugged or clogged up. I personally think your engine is either vapor locking from the heat or choking itself out from not having enough oxygen under the dog-house. I'd investigate this by trying to run it with the cover off on the water -- although maybe you already tried this and it killed as soon as you backed it into the water? How are you attaching a hose when you run it on land -- with a plunger setup or with a plumbed in hose?


Wouldn't water getting by the riser gasket into the heads cause this issue? Would also not have an issue unless water in exhaust system?

[BOWZ]

agree with the other post above, also weak starter/batt that can't turn the engine over fast enough to pop off with the back pressure created with the water in the supra traps? keep us posted.


bowz