Strange Problem! Any Ideas?
 

I have a wierd problem restarting my Starboard engine when it's hot. I have 500 HP's with B&M Blowers and upgraded mechanical fuel pumps. Port engine will always refire but the Starboard will not. When cold at the begining of the day both motors fire right up. After running for any length of time when shut done the Starboard motor is starved for fuel and will not start. Here's what I have done so far. New fuel pump, rebuilt carb, new fuel filter, replaced fuel lines and basicaly checked the integrity of the entire fuel system. All this to no avail, same problem still exists. Almost like a vapor lock of some sort. Any ideas on what the problem could be? What should I do next?

it seems you might have an ignition problem,what are you running as far as ignition system?

Are you getting fuel psi when cranking when its hard to start? Sounds like it could be ignition related like Mike said.

I know it may sound strange but what are you running for exhaust ? Maybe a leaky header causing this issue .

frist with any running problem u have to find if it;s fire or fuel the easy way to do this is to get the moter hot ,remove air cleaner spray fuel in the carb with a can of carb cleaner if it;s fuel it will crank right up if it doesn;t it will be a fire problem

Yes loss of fuel presure. Fuel bowls empty. Engine will fire momentarily until fuel bowls empty out. Not ignition, if you pour a little fuel down the carb it will fired for a moment. Definatly a fuel problem. Headers are Stellings green.

Check the tank vent for being clogged. Also, check the pickup in the tank for cracks, or any pre pump fittings that can suck air. The pumps don't pump well even with a slight air leak.

Most of the time we fire up when boats at ramp, with trailer under it. Fuel sits high at the pickup because of the angle, but when at rest in water, just the bottom of tube is submerged

When you shut it off the bowls will be full. Where is the fuel in the carb going?

Hey Kris, I think he mentioned it will start and run until the bowls run dry, then no start.

Yes that is correct.

This only leaves pickup tube , vent or extreme heat somewhere evaporating fuel . Very hard to diagnose without being there when it happens . Usually with problems like this it's something stupid that's getting overlooked because it's so simple . One of those " good thing it weren't a snake " moments . Good luck and scrutinize it a little harder .

Is the boat rigged with a single PU per engine, or a common PU for both engines?

Have seen Fountains installed fuel line from tank to ball valve collapse internally... only when bilge warmed up. The line looks good but has failed internally.

Ok, Thanks guys for the ideas. I will start in the tank and work my way to the carb again with a fine tooth comb. You're right it is probably something simple that I have overlooked. My buddy is going to come over and help me this weekend. Maybe a new set of eyes will see something I didn't. I'll let you all know what we find. Thanks again.

Make sure you don't have an inner liner of a fuel line collapsing once it warms up. I bought a 98 that had been sitting in someones garage and was like brand new except all the fuel lines were shot. I ended up re-plumbing everything.

The first thing I would do is swap fuel pumps from side to side. It sounds like the fuel in the lines may be leaking back past the pump diaphram.

take a piece of clear hose and a gas can. as soon as motor won't start, swap fuel line ti clear hose and crank motor. if it pulls fuel up and fires motor, it is definately pre-pump problem. if it doesn't pull fuel, it is farther downstream...needless to say, don't go driving the boat around with this jury-rigged system...

Does the fuel level have any effect? As in, full tank/no problem vs 1/2 tank/no start?

in the op,you stated that when the engine is hot it wont start,now you say it wll start and run until the fuel bowls run dry,2 different scenarios,please clarify exactly what happens when the engine gets hot after a hard run.

in post 1 he said he replaced the fuel pump,so i think he has eliminated the pump as the problem still exists.

I missed that part.
Also, when re reading, he said its fine when its cold, so the fuel pump is probably not the issue.

It sounds like the fuel is evaporating in the lines and causing a vapor lock type condition.

does the tank have a anti drainback valve,also known as a check valve?

fixx
 

if the pick up tube was cracked(at the threads towards the top of the tube) the engine would run fine with a full tank of fuel,then the engine would start acting up once the fuel level starts going down...

Does this sound familiar? if you do find a cracked pick up tube order 2 of them but the tube part made out of nylon..they wont crack..

proubably not your problem but worth a shot.have a mpi fuel injected motor and the sea water pump on the motor was weak,causing fuel to evaporate.let motor cool down would refire every time.not fimilar with your set up but the sea water pump is quick and easy to check.my engine didnt over heat or anything.just wouldnt restart hot