cannot get my 454 mercruiser to fire

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probie24

New Member
Nov 6, 2013
50
detroit river
Boat Info
1983 srv270
Engines
454 mercruiser w/trs outdrive and velvet trans
This has been driving me up a wall for the past few weeks. engine cranks but does not start. I have replaced the plugs, wires, cap, rotor, and the ignition coil. Still nothing!!! not sure what it could be, anyone have any advice? need to get it out of the water soon, don't have much time being its November and all
 
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Do you have a spark? A Harbor Freight spark tester is $3.00. Plugs in line with the spark plug wire. 3 things needed to run. Spark! Fuel! Compression!
 
+1 for spark, fuel, compression. Spark is the easist to check. Fuel can be tested with some starter fluid. Compresion with a compression tester.
 
Is there anything happening at all when it cranks? Does it fire? Backfire?

Does it spin quickly or slowly?

How long have you had the boat? Question I am asking here is have you run it before?




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I've had the boat for a couple of months, it has ran fine up until a couple weeks. it cranks like it should, and I was out there yesterday with a light tester and everything was showing power- coil and cap and distributor sensor. maybe the engine is flooded? I was looking inside the carb and there is a pool of fuel at the bottom.
 
got spark and fuel, a pool of it down in the intake if I look through the carb.....could it be flooded and if so what can I do about it?
 
Remove the spark plugs and crank the engine. This will remove the excess gas vapors. It also will give you an opportunity to check the condition of the "wet" spark plugs and clean/dry them. Should start quickly after you reinstall plugs. Good luck.
 
probie24 said:
got spark and fuel, a pool of it down in the intake if I look through the carb.....could it be flooded and if so what can I do about it?
Click to expand...

Ok that and your previous post is what i was looking for.

Flooded.....standard procedure, open the throttle to full and crank the engine, probably 30 - 60 seconds that should clear it, it may even fire, then pull it back to idle and continue to crank see if it fires.

The reason I asked how long you had had the boat, have you had a big block before? They can be a biiiiiiich to start. There is quite a few threads on it if you search. They drain the fuel back after a day or so. Generally you need to crank them for about a minute and do nothing during that period. Then 2-3 good pumps of the throttle, and they should fire.

I'm lucky I have fuel flow meters, so I actually watch the fuel flow, it will hit 30l then come back to 2l that's when I pump it, generally around the 1 minute mark.

They also struggle with the auto chokes....flooding the engines.....the PO of mine removed the auto chokes before they sold it to me, being a warm climate and a mechanic, I manage better without them. But you may want to check if they are stuck.

A previous post mentioned timing, which was also something I wanted to mention, if you have spark and fuel, the timing is also important, hence why I asked if it was backfiring, but timing can still be out.

Compression, but if it was running, I would think it should start, but may be down on performance.

The other possibility is fuel condition


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thank you all very much, hopefully this weekend ill be able to get it started and thanks again
 
Concur...sometimes it is best in these types of cases to step back, take a deep breath, and go back to the basics. Be sure plug wires aren't misrouted, that the distributor rotor is turning and that you actually have the points set properly or have an electronic ignition substitute.

According to your stats, its a 1983 boat...carbureated I'm sure.

There has to be spark to make detonation. Use a spark checker. If you don't have access to a spark checker and don't want to hold it in your hands and manually test (sub-optimal procedure), pull a plug, leave the wire on, use a vise grip and ground it to the engine. Spin the engine over and look for spark. If you have it, move to the next step.

Are you absolutely certain there is fuel getting to the cylinders? Taking the flame arrestor off and pumping the linkage should get you a shot of fuel from the accelerator pumps and confirm there is fuel to the carb. I get some flack from the other guys, but I like to take a small tank of propane with an adjustable nozzle and hose (sort of like a butane torch nozzle) and squirt some into the carb while spinning it over (starting fluid is a cruder but effective method as well).

If you know you are getting fuel and you know you are getting spark, then compression is the next step. Take a compression test of any cylinder and be sure you have compression...in your engine, I would think I would want to see compression results of at least 110-125 psi. For best results, take all the cylinders and be sure there isn't something off kilter. 10% difference between the highest and lowest is the standard for concern.

If you know you have fire, air and compression, then the only other issue is timing...they aren't getting together at the right time. For that, you have to get a little creative. You want number one cylinder at top dead center on the compression stroke, and then look to see that the rotor is actually pointing to that particular plug wire in the distributor.
 
Darn, sorry, got distracted and worked on this over the course of several morning calls. In the interim IanBat had a perfect response.
 
oh I forgot to mention before this whole fiasco started I put some fuel stabilizer in the tanks. after that I started it, it fired up but then stalled which is normal so after that it just cranked and cranked and cranked. and then I believe I flooded it
 
If this has been going on for a few weeks, as you said in post #1, it can't be b/c the engine is still flooded. If it is continually flooding than there's something else wrong that is causing it to NOT start and thus get eventually flooded. Is that engine electronic ignition? or do you have points?
 
rondds said:
If this has been going on for a few weeks, as you said in post #1, it can't be b/c the engine is still flooded. If it is continually flooding than there's something else wrong that is causing it to NOT start and thus get eventually flooded. Is that engine electronic ignition? or do you have points?
Click to expand...

electronic thunderbolt 4 but could it be because of the fuel stabilizer?
 
I think you said you had spark - my problem on my previous boat was no spark. Traced it to the IGNITION SENSOR, which is a gadget in the distributor cap. Swapped it with the one from the other engine and it fired right up. If you have spark then your ignition sensor is OK.

SIE-18-5116-1_lg.jpg


#8 in the pic below...

41255.png
 
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I did change the sensor, I think I forgot to mention that earlier but I think it could be the flooding because I was constantly using the throttle when starting the thing everytime I changed a part and never even thought that was actually the problem. Hopefully i'll have it started this weekend and if not you'll probably see some more threads. anyways thanks for all the advice I really appreciate it
 
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