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Gas Engine Help Requested

  • Thread starter Thread starter dave1985
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dave1985

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Sep 5, 2007
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  1. OWNER - I own a Hatteras Yacht
Hatteras Model
36' CONVERTIBLE-Series II (1983 - 1987)
I have a 1985 36c with 454 Crusaders. The ignitions were changed to Mercruiser Thunderbolt IV at some point.

This spring at first start up, the port engine ran fine for about 10 minutes and shut itself off. We restarted and it shut off again after a couple minutes. Each restart resulted in less time before shut off and harder starting. Thinking it was fuel starvation, we changed all filters but no change. We then changed cap and rotor and everything was good.

Same problem reoccured last week. We ran thunderbolt ignition troubleshooting procedure and changed sensor in distributor. We currently have the engine starting, sometimes with a little struggling and run fine for 10 or 20 seconds and then losing power and shutting down. The tests say everything ignition wise looks fine. We are getting spark from the cap center tower when turning over. We changed the cap and rotor but still have the same issue. I can look down into the carb and see gas entering when the throttles are moved. Removed the fuel filler cap to see if maybe the vent was clogged and there was no change.

If it's been sitting, it starts quickly. In restarting, it may or may not start rough but when it starts, it runs fine for 10 or 20 seconds then the rpms drop, if you throttle up, it comes back momentarily, then drops down and soon shuts down. No backfiring.

Any ideas where to turn next?

Thanks for any help.
 
if the fuel is old I would try running the the engine off a small tank of fresh fuel before doing anything to crazy.
 
Do you have a vacuum gauge at the fuel filter? Could be an obstruction at the pickup tube or anti siphon valve
 
Try starting fluid. If it'll run on that then it's not the ignition. My wife's tahoe didn't have a fuel rail schrader valve so I couldn't test fuel press. It ran on starting fluid so it ended up being the fuel pump.
 
Could be the carb. The float and needle valve could be gummed up.
 
If you have good spark. Pull the fuel line to the carb off. There should be a small in line filter or screen at that junction. Be sure it is clean. With the fuel line off check that you are getting a full line diameter of fuel. Best to do with two people, one to hold a container to catch the fuel (not one that can dissolve in gas) and one to crank the engine. If you get plenty fuel I would suspect the carb. If not then the fuel pump or some times if the boat is fitted with those quarter or half turn shut off valves they can suck air. Most have an o-ring in them that will get dry and suck air. They can be revived by lubing the o-ring with a little grease or the like. You can also check if the anti siphoning valves in the top of the fuel tank are stuck. If the boat sat for a months with ethanol gas, the carb could be gummed up and only cleaned by disassembly. Ethanol gas leaves contamination in the carb that looks like cooked tapioca or small fish eggs. Good luck
 
Thank you, all.

I'm assuming carb with outside chance of fuel pump. Before I take the carb off and send it to a shop one other question. Would it likely be impossible for the ignition module to work correctly for test and for checking a spark but then fail on a consistent basis 20 or 30 seconds after starting?

Thanks again.
 
Yes the thunderbolt modules can do intermittent failures like you are experiencing. I've had it happen one or twice. (very rare though). The best and cheapest way to troubleshoot this is to swap modules on each engine and try it out. If your "good" engine is now bad, you know the problem. It will take about 3minutes each to swap them over.

Does it start up fine when cold? I've also run into coils getting hot and doing goofy things too. Again, a quick swap will make diagnosing go fast and cheap.

If it's the module, check ebay and other online used sources. They are like 300-400 new last I remember. They hardly go bad. Some people claim each engine has a different part number, and I guess the timing curve may be slightly different, but you should be able to find the same PN.

Intermittent failures are rarely fuel related in my experience. I did have a problem once where a boat would idle fun, and run perfect up until about 3/4 and die. It'd idle all day. Sorry, I lied...had two boats like that: one had a stick stuck in the fuel pickup, the second one had the inlet needle valve seat backout inside the carb--this made a very small opening for fuel to trickle in.

Come back here and let us know how it goes.

PS: when the pickup sensor fails, it's usually all or none. I don't recall ever seeing it be intermitentnt. Following that simple flow chart helps isolate the components, but ther intermitant ones can be tricky. Luckily you got two engines to swap with!
 
With 2 Crusaders you have the ability to swap anything and everything for trouble shooting. If you can still see gas squirting after it shuts off, it probably is an ignition problem. If you have a timing light swap the entire distributers, caps and wires. Yes, they are the same as the cams both turn the same way. I could explain that if needed. The carbs can also be switched. The fuel pump could also be a problem, but, again, if the gas will squirt immedietly after shutdomn by moving the throttle back and forth, I can't imagine that fuel is your problem. I would also buy some "sea foam" and pour it slowlydown each carb as it tells on the can. I do this each year.
 
Mech or elec fuel pumps?
Gary
 
Dave1985,
There are great suggestions here. IMHO, your issue sounds like fuel. We have been walking down a similar path With our 427's and with much thanks to this forum we are getting things fixed bit by bit.
You may find a cross over valve on your fuel line, that allows drawing of fuel from the other fuel tank. Try that. What happens?
What we have found so far:
1) We ran fuel directly to the engines from two 5 gal Gerry cans. The result was awesome. No lag, no rpm surging. That pointed the finger at the fuel line.
2) Again as a result of this forum, we found electronic fuel shutoffs (anti-syphon) in the gas line. We took these out of the system by simply bypassing them. We found that they were packed with tank crap, and ened up 'snaking' the fuel lines out. The engines ran better with these obstructed shut offs taken out. Better, but not yet perfect.
3) We replaced the fuel line filters with spin ons. (We took 3 old filter cannisters right out; newer filter technologies seem to be better than older-certainly they are less prone to air leakining).

Whats next?
Now we are looking at carb rebuilds, (frankly a cheap date). We will also pull the fuel pick ups and check their screens.
I will report back here afterwards.
Good luck, keep sharing your results, positive and not.
Sailor John
 
Thanks Jim! Some GREAT info here! Back to Dave1985:
Dave I didn't know about the screens at the carb, so I would check them too.
Sailor John
 
Sorry John, I was unclear. The 427's have the carters. I don't know what the op 454's have.

Jim
 
Can somebody explain to me how an engine that runs for 10 second then dies but starts up again is fuel? And if it dies and is allowed to cool and starts right up again...but how can it do that if no fuel is in the bowl.

And from that pcv drill out link...are ya sure that isn't meant for the brake booster. Without a pcv valve or at least pcv orifice, that guy just created a big vacuum leak.
 
You mentioned there was spark at the center post on the distributer, have you tried checking for spark at the spark plug itself?

We had a similar problem, only on a diesel. What happened is there is a support of sorts on the bottom of the fuel tank. The support had come loose and worked it's way under the pick up tube, engine would die and stall, thinking it was bad fuel, or dirty fuel filters, I changed several filters, each time everyting ran fine for a few hours, then act up again. I figured it out by cross feeding from the other tank which eliminated everything but the tank.

I cut into the tank, and had a fiberglass guy resecure the offending support piece.

Either Hatteras or possibly Sams will probably have the drawings of the tank, if you have to open it up.

Using a 5 gallon can of gas to run the engine is a great idea, I think I would hook it in right at the carb, and eliminate the supply system entirely for a first check. I have also heard of rubber fuel lines seperating or delaminating and the inside layer collapses, not readly visible by just looking at the line.
 
We attached the 5 gal Gerry cans right to the fuel pump. Worked great. Didn't go far, but far enough to know our surging issue was fuel related.
 
krush said:
Can somebody explain to me how an engine that runs for 10 second then dies but starts up again is fuel? And if it dies and is allowed to cool and starts right up again...but how can it do that if no fuel is in the bowl.

And from that pcv drill out link...are ya sure that isn't meant for the brake booster. Without a pcv valve or at least pcv orifice, that guy just created a big vacuum leak.
Click to expand...

krush
the 427's have a pcv and the drill out offers the same functionality as the original carter carb.
 
Sailor John said:
We attached the 5 gal Gerry cans right to the fuel pump. Worked great. Didn't go far, but far enough to know our surging issue was fuel related.
Click to expand...


i was hoping you had connected further back like before the fuel filter. that would have verified from there on was sound. since your shutoff switch had so much junk stuffed in it i would check all fittings, shutoff valves and fuel manifold for junk. the tank top fittings also. along boatnut lines, someone else here had a similar story of a foreign object restricting the pickup in a maddening fashion. checking the rubber fuel lines is a good suggestion also. there is a specific type that is rated for use with
ethanol, sorry i dont remember the name. the old stuff gets eaten by it.

jim
 
This is waaaaaay out in left field, but my 1976 Chris Craft Marine Power 454 engines in my Hatt were losing power and it turned out to be the distributors. They were advancing all by themselves. Replaced them with electronic ones and never had the problem again
 
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