Why won't my boat start when it's hot?

[lundberg]

My 94 Prostar 205 with the 350 TBI starts fine when its cold, but once it's up to temp if I let it sit a couple minutes it is hard to start. It use to take three or four tries, but this morning it was more like 7. It runs fine once it is started and will start up fine if you turn it off and then right back on. Anyone have any suggestions. I've got a private lake rented in a couple weeks and don't want my boat to die while we are there.

[Jody_Seal]

sounds kinda funny but keep a red cup or something you can fill with cool water and utilize it via pouring cool water over the fuel pump a couple of times. Another Idea would be to prop up the motor box during hot soak and let the engine compartment ventilate all the engine heat into the surrounding atmosphere, you are probably suffering from vapor lock.

[lundberg]

Thanks @Jody_Seal , I'll try that. So if I took the flame arrestor off I would see no fuel spraying out? Are there any tricks to fix it?

[gregy]

I just went through the same in my Toyota truck. But I also noticed my mileage dropping. I installed a new set of injectors and it runs perfect. There's not a lot to those TBI systems. Have you checked your Fuel pressure? Could be a bad regulator or pump if the pressure is low. If it is vapor lock I know there a lot of talk on Malibu mfi engines of putting a booster pump near the tank. The new fuels with more alcohol tend to Vapor lock easier especially at higher altitudes.

[markchilcutt]

Our old 06 Malibu with the 340 monsoon would do the same thing (vapor lock) on really hot days and yes @gregy we are at high altitude. I would cycle the key on and off a few times or have to remove the fuel line from the bottom of the electronic fuel pump to remove the vapor. @Jody_Seal good idea on pouring cool water over fuel pump. If using higher octane gas 91 it doesnt seem to be as bad.

[Orlando76]

Is it acting like a dead battery and its struggling to turn over? Check timing and coils seem to be finicky sometimes when they get hot. Does opening up the throttle help? Are plugs looking wet? When you shut off engine once hot, check to see if you continue to see fuel dripping down throat ( you shouldn't).

[JohnN]

Ethanol on a hot day is likely the problem. Before you go, insulate the fuel lines and the fuel pump if possible, when you're there prop the cover up with something when taking a break and it should help.

[lundberg]

@Orlando76 sometimes the first time I turn it over it struggles (I know the battery is good and I just put in a new starter). After the first time, it turns over strong. How does that relate to timing and coil?

[303Skier]

I'm having the same issue with the same engine @lundberg. It's been driving my dad and I nuts! Our boat mechanic told us the fuel is very bad this summer because of the high amounts of ethanol in the gas. We've been lifting the engine cover when we kill the engine. Also some cold rags placed over the manifold and fuel pump and lines seems to help. Even our Honda generator has been vapor locking :(

[303Skier]

May not be the issue but good idea to go ahead and replace the IAC valve too. Ours was bad but still didn't correct the cranking issues, only improved ideal and high rev to ideal.

[Stevie Boy]

Check the earth lead on your battery to the anchor point, make sure it,s clean good contact, shot in the dark but simples, when things get hot resistence drops.

I owned a E Type Jaguar that done excactly that , extra earth lead direct to the engine fixed it

[WBLskier]

All good suggestions...I had the same problem with my old 89 prostar. Turned out to be the kill switch was going and it was an intermittent problem. Bypassed the kill switch and problem solved. Not sure why it didn't ever turn the boat off when running, but it didn't. It only happened after the boat was up to temp and then I turned it off. Super frustrating.

[303Skier]

@lundberg I would highly trace the hard cranking to vapor lock. Looks like in Washington you can have up to 10% ethanol in the fuel.

 

http://www.fuel-testers.com/state_guide_ethanol_laws.html

 

Also see this about ethanol:

 

"The relatively low boiling points and high vapor pressures of methyl and ethyl alcohol indicate that vapor lock could be a serious problem, particularly at high altitudes on warm summer days. Vapor lock occurs when the liquid fuel changes state to a gas while still in the fuel delivery system. Vapor lock can cause reduce engine power or stalling."

 

[Orlando76]

If your timing is too advanced your starter will try and turn the crank one way and combustion sequence is going the other way and it'll act like the starter and or battery doesn't have the cojones to crank it.

[303Skier]

@Orlando76 The 350 TBI has electronic ignition, the ECU will advance or retard timing even if the baseline timing is off.

[Orlando76]

Didn't think about that..... Kinda like the dreaded pro tec ignition.

[ncskier]

I had the same problem on my 350 tbi indmar. It turns out the lower pressure fuel pump went bad in it.

[WayneCammidge]

I have a very old 1992 Ski Nautique. Okay it still has the carb, but was having a few issues with perculation (vapour lock), so I fitted an electric pump that comes on as I turn on the ignition, turn it on and leave it on a few seconds before starting refills the carb before you try and crank. Huge difference. Then I plumbed in a deck was pump that gives me a hot shower on board while the engine is running, but through solenoid valves, relays and timer relays have made the pump, pump cold water through the engine on shut down for a minute. That really stops the heat soak.

Most times the engine will just fire straight back up on the key only