Mercruiser 2003 4.3 V6 carberated engine was running fine and started up normal after a moderate run . Was idling in neutral to retrieve anchor and engine shuts of and fan belt came off. Tried to start and heard the engine won't crank and suspected hydro lock. Boated back to slip on other engine. Remove spark plugs and found water in a few cylinders. Remove risers and observe water inside manifold. Drained all water , reinstalled risers and plugs but unable to start . Engine cranks fine , spark is present, fuel is in carb, . Swapped carb , coil and ignition module with working engine but still no start . Checked compression on 1 cylinder was good . Gas is from recent refill and on a common tank with the working engine. Disconnected fan belt to rule out water rentering the engine , raw water cooled systems and drained remaining seawater from engine. Besides checking compression in the remaining cylinders I have no ideas where to look next . There is no sign of starting , no cylinders firing or backfiring.
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No start after hydrolock
- Thread starter bdreger
- Start date
Good job checking so many suspects.
Was the cylinder you checked compression in one of the ones that had water in it ( and could have blown a head gasket)?
Where did you check spark -at the plug or coil lead? Nice bright blue arc?
As Bruce suggests, checking timing could point to loose distributor base or timing gear problem.
Just in case the cylinders are gas-flooded, I think I would try cranking after securing choke open, advancing throttle lever to WOT to stay open ( being ready to move immediately to idle if it fires up) and spraying a little starting ether down the carb throat. Just don't keep doing that.
How old are the ex. manifolds & risers?
Was the cylinder you checked compression in one of the ones that had water in it ( and could have blown a head gasket)?
Where did you check spark -at the plug or coil lead? Nice bright blue arc?
As Bruce suggests, checking timing could point to loose distributor base or timing gear problem.
Just in case the cylinders are gas-flooded, I think I would try cranking after securing choke open, advancing throttle lever to WOT to stay open ( being ready to move immediately to idle if it fires up) and spraying a little starting ether down the carb throat. Just don't keep doing that.
How old are the ex. manifolds & risers?
Hi thanks for the response , I checked all the wiring , but still have to check ignition timing and compression in the other cylinders. The one that I checked seemed to hav ine the most water in it . I'm using a spark tester inline at the coil to distributer connection. The spark light level inside the tester is comparable to the other working engine. The risers and manifold are new from last year . The exhaust flappers are worn and one is stuck open ,which would explain the water getting in ,but at the slip it's pretty calm and when I pulled a plug again it was dry . I tried all methods of throttle open , opening the throttle band hand observing fuel spraying into carb , starting fluid , there's never the slightest indication of any cylinder firing . It's hard to rationalize how it got to this state , I suspect ignition timing , somehow it's either way off. The distributor is secure and didn't move . Thanks again, I'll continue testing today I hope .
Checked compression is good , 150 in all but 1 cylinder which is at 170 . Odd ,but don't think it's a showstopper. Checked timing with induction lamp on cylinder 1 and looks normal when cranking . Checked for spark on all 6 plugs by removing plug , touching it's case to ground and verified spark . Spark is a little weak but present. Removed valve covers) rocker covers to confirm rocker arms and pushrods are moving. Interesting that with the covers off there was a slight hint of starting for a second. Also the pcv valve on 1 side was clogged. My final thoughts are to replace plugs , wires , cap and rotor since they are all very old .
What is the engine's full model # ands serial number?
You are doing a great job and it certainly is surprising so many suspects appear to check out OK.
If you have corrosion on the cap electrodes and rotor it would certainly be wise to change them, and the rest. You could compare the coil and plug wires resistance readings compared to the those of the working engine.
When the all the plugs are out, I'd suggest cranking the engine (w/ choke & throttle open) to reallyclear out the cylinders again .
You could check whether the #1 cylinder is at TDC on the compression stroke when the dist. rotor points at the normal position of cap electrode for cyl. #1. That's when the dot on the camshaft gear and timing gear ...should ...still be next to each other.
Never hurts to triple-check firing order at both ends of the cables. Looks to be CW 1-6-5-4-3-2 .
And when next trying to crank to start, no pumping and again try ether/start spray once with choke & throttle plates open for best chance at quick combustion. When you checked the accelerator pump spray, did it smell nice strong/gassy? (Really long shot- If the pickup for that engine was lower than that for the "good" engine it ...could... be supplying water or phase-separated water/ethanolat the bottom layer.)
Even though you are seeing some level of spark, you could try bypassing the lanyard kill switch if there is one. And maybe check the oil pressure switch connections and the switch itself. And if the engine has an Alpha drive with shift interrupter check that too.
Compare all to the good engine . A slight short to ground or almost-open ( weak connection or mostly broken wire ) circuit anywhere in the ignition start circuit could drastically affect chance of combustion yet allow weak spark. Is the only ignition module on those engines in the distributor?
The only other things I can think of are timing gear is out of whack or exhaust is clogged (though you know where the flappers are) .
Did you ever check the oil to see if water made it there?
You have(?) to be really close! Sorry it is giving you such a run. Best luck.
You are doing a great job and it certainly is surprising so many suspects appear to check out OK.
If you have corrosion on the cap electrodes and rotor it would certainly be wise to change them, and the rest. You could compare the coil and plug wires resistance readings compared to the those of the working engine.
When the all the plugs are out, I'd suggest cranking the engine (w/ choke & throttle open) to reallyclear out the cylinders again .
You could check whether the #1 cylinder is at TDC on the compression stroke when the dist. rotor points at the normal position of cap electrode for cyl. #1. That's when the dot on the camshaft gear and timing gear ...should ...still be next to each other.
Never hurts to triple-check firing order at both ends of the cables. Looks to be CW 1-6-5-4-3-2 .
And when next trying to crank to start, no pumping and again try ether/start spray once with choke & throttle plates open for best chance at quick combustion. When you checked the accelerator pump spray, did it smell nice strong/gassy? (Really long shot- If the pickup for that engine was lower than that for the "good" engine it ...could... be supplying water or phase-separated water/ethanolat the bottom layer.)
Even though you are seeing some level of spark, you could try bypassing the lanyard kill switch if there is one. And maybe check the oil pressure switch connections and the switch itself. And if the engine has an Alpha drive with shift interrupter check that too.
Compare all to the good engine . A slight short to ground or almost-open ( weak connection or mostly broken wire ) circuit anywhere in the ignition start circuit could drastically affect chance of combustion yet allow weak spark. Is the only ignition module on those engines in the distributor?
The only other things I can think of are timing gear is out of whack or exhaust is clogged (though you know where the flappers are) .
Did you ever check the oil to see if water made it there?
You have(?) to be really close! Sorry it is giving you such a run. Best luck.
Success! Changed plugs , cap and rotor. Didn't start right away, but now it starts up right away. Suspect the spark was just not strong enough and maybe like Sandy mentioned,the fuel pickup on that engine is slightly height different and pulling in some bad gas . Let's see how it goes, I didn't take it out of the slip yet . But it sounds good and starts right up now .
Thanks to all , it's comforting to have a little support group like this.
Thanks to all , it's comforting to have a little support group like this.