Runs 2 hours and then quits.

[crunch1]

86 SEA RAY Seville 4 cylinder 170 HP. The last 2 times I have been out, after 2 hours the motor looses power,backfires once or twice, and acts like it is loading up. I have checked fuel/water filter, plugs, wires, points rotor, cap. No real problems found. I don't know the hours on the engine. It runs great for the first 2 hours 4700 rpm wot, or below. I did find coolant down about 1/2 gallon. Have not run since topping off.
Any and all help greatly appreciated. Could it be the anti siphon valve sticking?

 

[OldSkool]

Loosen your fuel cap if it happens again and see if there is a vacuum. I seen this happen with the clogged vent. The little ball valve stuck after sitting over the winter.

 

[SCORPIO]

Could also be a coil heating up and breaking down. Check the fuel vent like Oldskool mentioned first.

 

[Lazy Daze]

A failing fuel line is a possibility (especially if they're original), but that would likely show symptoms sooner than two hours.

What were your engine temps showing?

Another option - a crack in the fuel pickup tube. If each time you have topped off the tank afterward, this one has some merit. If you didn't top off the tank between the first and second time then proceed with the other suggestions.

 

[OldSkool]

Dennis, I have replaced the fuel pick up on equipment for this issue. The tank would get to ¼ full and the engine die. After refueling the machine would run perfect until the tank ran down again. Vibration would cause the line to break ¼ way up the tube.

I agree that a fuel line would cause the issue much sooner. One thing to consider is vapor lock. OldSkool would lose power and die after about an hour and a half of WOT pulling a tube. The engine compartment would get so hot that the intake manifold would vaporize the fuel before entering the engine.

After sitting and letting the engine cool down it would start a run perfect until the compartment got hot again. I found that we were storing the fenders in the engine compartment venting channels running down the side of the interior. :smt021

 

[crunch1]

Thanks for all the suggestions. The vent line is clear, but I will recheck to be sure. The engine temp was 170 F. I found the low coolant after last time out. The coolant line had a very loose plastic clamp on it, replaced with metal screw clamp. I was surprised temp was not higher. The coil is suspect in my mind so will pick one up. I'm going to temporarily pull the anti siphon valve and see if this has any effect. Will most likely go out tomorrow. I will post results. It gets a little testy docking on the Ohio river without power.

 

[crunch1]

When I started to remove the coil, printed on it said external resister required. Can anyone tell me where this might be located?
Thanks

 

[OldSkool]

You may still have points in the distributor. The resister lives in there. It's a little round cylinder with a wire coming out on end attached to the points. If you take the cap off and just under the rotor, it is bolted in there. Replace the coil and you should be good.

 

[SCORPIO]

Oldskool are you maybe thinking of the condensor? I've never seen a ballast resistor inside the distributor cap before. Usually they are located near the coil on the manifold or even attached to the coil itself. If the OP just uses a new coil of same specs, he should be able to install it without changing the ballast resistor.

 

[OldSkool]

You are correct. It's the condenser. Man do I hate senior moments. The resistor was used on a lot of Dodge products back in the day. A little ceramic bar with a wire coil wrapped around it if I remember correctly.

Thanks SCORPIO for the catch.

 

[Rick K]

When I started to remove the coil, printed on it said external resister required. Can anyone tell me where this might be located?
Thanks

You may or may not have an external resistor, but on my '81, it's a brown wire that runs off the coil, then back down thru the wiring harness, folds up a few times, etc., then stops (or at least from what I remember it does). That is supposed to be the resistor. Anyhow, I had the same issue, coil heating up and stalling out the engine, after x amount of time at wot.

 

[geo737]

crunch1 , I had the same issue with my SRV, like OldSkool, my engine compartment would get hot enough to cause a vapor lock. To help combat the problem I installed a heat shield used on older Chevrolet cars and trucks, (not sure if other mfg's used them), it is basically a aluminum shield mounted between the carb and the manifold. it affectively acts as a shield to reflect the heat away from the carb. Another thing I did was to replace the metal fuel line from the pump to the carb with a flexible line that was long enough to route away from the engine block. Unfortunately, with ethanol fuels, (if thats what you are having to use), the boiling point of the fuel is reduced due to the alcohol and will not help a situation if you are already on the edge. If you have the heighth room, an insulator made of phenolic block might be of help to reduce the heat getting to the carb.

 

[JVM225]

If fuel is not a problem (engine getting fuel), then it is probably an ignition issue of some sort. Could be the coil, ignition module, distributor, pick-up, etc.
The coil and pick up in the distributor are fairly inexpensive, and may be a good place to start. If neither solve your problem then it's time to start looking for an ignition module. I had a similar problem years back on one of my original motors. The culprit was a bad Thunderbolt IV ignition module. It would cut out after a while of running, I would limp back on one motor, and the next day the motor would start again.
I was fortunate in that I had two motors and was able to isolate the problem by swapping parts from one to the other until the problem moved over. That isn't possible with a single engine, so it's probably better to start with the cheapest stuff first.

 

[crunch1]

Changed out coil, plugs, wires, anti-siphon valve,[which did have some corrosion build up],and fresh gas. Took it out for a run yesterday in the heat of the day. Boat ran really well, wot 4500 rpm, temp around 170 F. Idle was around 800 rpm and temp dropped down quick. motor sounded like it should and ran well at all speeds for 90 or so minutes. Time was a factor in checking things out. Not cheering too hard yet, but feeling a lot better about the performance. Will take it out for a longer run when it gets back from the canvas shop towards the week end.
Thanks for all the advice and comments. It did feel good to be back to work on old school type of motor without all the electronic add on's to make the EPA feel better.
Have a great day !

 

[crunch1]

After the problem continued, I finally went to a repair shop I trust. They found the weights in the distributor stuck wide open. They cleaned out all the old grease, etc. and put back together. I had them put in on a dyno for an extra charge. They ran it at several different rpms and said it appears to be in very good shape. I have to take it out again, but since I run a campground and it is a holiday week end it will probably be next week before I can.