Engine firing problems

"Help! I have a 5.7L, V8 Mercr

"Help! I have a 5.7L, V8 Mercruiser, 1988 which has always run well until this year. In Feb.2006 we had some difficulty in starting the engine - it always smelt as if it was flooding. Had a full service done then had trouble with the engine stalling going into gear - forward and reverse. The fitted stripped the controls and renewed the throttle cable, an improvement but the problem remained. I took the boat out to sea, after half a mile, opened her up but could only get 1500rpm, brought boat straight back. The fitter found water in the oil and announced the head gasket had gone, no compression on one side. We sucked out the emulsified oil and replaced with new oil and filter. Took both heads off, they were skimmed and serviced. Fitter could not return for 2 months so we topped up the engine with oil and turned the engine over weekly to lubricate the cylinder walls. 2 months later, no fitter! Another fitter, fitted the heads but engine would not turn by hand, only by ignition key. Timing was reset as best we could - no change. Thought it might be a bearing pinching on the shaft, this was changed but the engine will still not fire. Can anybody help please?"

"Ken, Some simple things to c

"Ken, Some simple things to check. Does it crank fast enough to start? Does it fire at all?I assume the distributor was out. It could be 180 degrees out when reinstalled and still have the timing mark at TDC. If installed correctly do you have spark? Is there fuel going into the engine? What bearing pinched the shaft? Strut bearing? Curiosity question: Where are you from?"

"Thanks for your reply. The c

"Thanks for your reply. The crank does turn fast enough to start, no, it has not fired. I have turned the distributor 180 degrees and it was just spitting back thru the carb. There is a spark, the plugs don't get very wet, but you can smell the fuel on them. The bearing that was replaced was the gimbal bearing. I have had the starter motor checked and found to be OK. Also, I have bought new battery. This is my first boat, I am not very knowledgeable about inboard engines, so all help will be greatly appreciated. I live in mid-wales, UK."

"Hi Ken,

It sounds as

"Hi Ken,

It sounds as if you are a couple teeth off on the distributer or timing chain slipped. If you align TDC on the harmonic balancer and number one cylinder has both valves closed is the rotor pointing to number one spark plug wire? Is the firing order correct? I'm thinking your motor is a GM 350. I believe the firing order is 18436572. Have the plugs been replaced?"

"You did not mention wether ma

"You did not mention wether manifolds were replaced. remove spark plugs, and turn engine over. check for water in cylinders."

"Thanks very much for your hel

"Thanks very much for your help. The plugs have been replaced. The motor is a GM, I will check the firing order and the position of the rotor arm as suggested, when I go to the boat this weekend. The manifolds were not replaced but I will check for water in cylinders as suggested. I have had engine trouble since Febuary this year and I am really grateful for this valuable advice and help."

I would check compression agai

I would check compression again.

"Went to the boat this weekend

"Went to the boat this weekend, there was too much wind and rain to take the covers off. I have checked the firing order and it is as suggested 18436572 and the motor is a GM 350. For info, the recorded hours are just over 900. Soon as weather breaks, will try your suggestions. Thanks everyone for your much needed help. One question remains though, what is a harmonic balancer?"

"Good morning Ken,

At

"Good morning Ken,

At least here in the US it is morning. The harmonic balancer, also known as a damper is what is mounted on the crankshaft with the timing marks on it. Is it called something different in the UK? Have you adjusted the timing to atleast TDC using these marks."

"Good evening,

It is evenin

"Good evening,

It is evening here in Wales with the wind blowing hard and plenty of rain. Thanks for your translation, I now know what a harmonic balancer is! Unfortunately, work is getting in the way of my quest, I will not be able to go down to the boat until 8/12/06 or 12/8/06 - whichever suits. Thanks again for your advice, Ken."

"Hey there
We have a Mercruis

"Hey there
We have a Mercruiser 5.7L ski that started being really hard to start throughout winter. First day out for summer(we're in NZ), it could only get 3000rpm max at WOT then stalled then just wouldn't start anymore.
The answer in our case was that the ballast resistance of the coil should have been getting 12V when cranking and was only getting around 6V for some reason. We decided to use the existing wire leading to the ballast resistance to control a relay(switch) that gets its power straight from the alternator and delivers to the ballast resistance in front of the coil. Engine now starts first pop, runs nice and coil ballast resistance is getting prescribed voltage.
Hope this helps."

"It's been a hectic couple

"It's been a hectic couple of weekends but we now know the sad truth - the engine has had it! We have tried all your helpful hints, still no joy. Took off the heads again, found a couple of bent push rods so then decided - engine out of boat and what a mess. Bent conrods, gudgeon pins seized so a complete engine rebuild is underway. We are lucky it did not start also block and crank are OK. Thanks to everyone for their advice, I will keep on reading this board and once she fires will let you good people know. Merry Christmas and and happy boating 2007. Ken"