Mercury 65hp Thunderbolt Ignition... is screwed ;( Im no mechanic either

[y2jericho]

2 cylinders don't fire really. When they do its occasionally like the motor is sneezing. Theres hjoles in hte outboard body and water is coming into the engine bay and leaking out 3 holes out of the sides. My mechanic said, because there isn't enough water pressure the third and fourth cylinders (the 2 bottom ones) are firing whenever they get enough pressure aka at high rpm's but when at lower rpm's they fire hardly ever and give a sneezing like punch and a puff of smoke comes out of the exuast and the whole motor jolts to the right or left. He is a trusted mechanic but i hvae heard this is relating to other things.. its a Mercury 1970 Thunderbolt 650cc 65hp. One of the most stylish "older" engines i have ever seen (with the chrome etc.) and it really suits my "older" boat <br /><br />I had a feeling it was the carbs but then again petrol wouldn't really build up and then fire causing the jolting. <br /><br />To fix the holes up to he has to remove the entire engine block and everything then seal the screws where the lower unit water shoots up through.<br /><br />Its been a medium priced lesson for me but i will konw my **** for hte next motor/boat i buy just by starting it (mechanic friend taught me heaps recently good mate of mine)<br /><br />anyway g'day/g'night whatever it is overthere and a hello from the land downunder

 

[y2jericho]

Re: Mercury 65hp Thunderbolt Ignition... is screwed ;( Im no mechanic either

anyone please

 

[Trent]

Re: Mercury 65hp Thunderbolt Ignition... is screwed ;( Im no mechanic either

First of all you need to do a compression check on all cylinders to tell their internal condition. Second (Sneezing) is usually a lean carb condition. Check the compression first, Then check for fire at each sparkplug. If you have fire, and compression is over l00psi and all cylinders are within 15 percent of each other....Rebuild the carbs with new kits.<br /><br />I really did not understand your question on the "water in the engine bay".

 

[mellowyellow]

Re: Mercury 65hp Thunderbolt Ignition... is screwed ;( Im no mechanic either

as far as I know, water pressure has nothing to do<br />with spark? I would follow Trent's advice and post<br />back results of test.<br />M.Y.<br />'70 merc 1150

 

[y2jericho]

Re: Mercury 65hp Thunderbolt Ignition... is screwed ;( Im no mechanic either

compression is within 6 of eachother <br /><br />like where the block and the outside harsness is screwed onto the aluminium casing of the engine and lower unit . water is seeping through and building up around the engine block then coming out the holes on the sides when it shouldn't (i think)<br /><br />The spark plugs are perfect and everything. So you guys suspect that the last 2 cylinders are being screwed up by one of the 2 carbs? Would this cause one cylinder to work ok sometimes/mostly all of the time and the other one to jolt ona dn off when it pleases?<br /><br />Once again you guys have been a mass of help.<br /><br /> thankyou

 

[dkondelik]

Re: Mercury 65hp Thunderbolt Ignition... is screwed ;( Im no mechanic either

Sneeze? Yup, Sounds like Trent is on it. Given that compression is with 6 lbs on all 4 cylinders AND good spark on all, then yes, I'd look at the carbs. Clean/Rebuild. Rebuild kits are are not expensive. I've heard that carbs clean-up well in the dishwasher but havn't tried it myself (I like my wife and want to keep her). <br /><br />Not aware of water pressure having any influence on ignition.<br /><br />Water/Water Pressure????<br />Where is the water comming from? Can you add more detail? From here it sounds like it is leaking at the exhaust housing gasket (power head bolts to leg). Was this resolved when your mechanic "seal the screws"?<br /><br />Good Luck, Good Boating.<br /><br />P.S. Carbs are synced? Timing is OK?

 

[y2jericho]

Re: Mercury 65hp Thunderbolt Ignition... is screwed ;( Im no mechanic either

Mechanic hasn't done anything yet i have put him on hold. Whats happening is the water is coming up through the leg from where you connect the hose when your running it on your back yard. Going all the way up then where the actual "motor housing" is bolted on to the lower unit there is water coming through that screw and filling up the top engine bay (the room around the block) and nearly covering the lowest spark plug and plug with water but i would have to have water goign in on full. Maybe when your in the water, water probably won't get into there because theres different pressure but im not sure as i didn't pay attention when i was on the water.<br />I know that the water hose is not leaking as it is perfect. The water then when it builds up around the block goes out through the holes on the sides of the bottom motor housing which in return removes all the water quite quickly. Is this normal?<br /><br />I'll try cleaning the carbs just like you said, roughly how much do the rebuild kits cost and is it easy to rebuilt a carb if you don't have a manual as i don't . <br /><br />Thanks for the help once again

 

[Solittle]

Re: Mercury 65hp Thunderbolt Ignition... is screwed ;( Im no mechanic either

You will need a manual to do the carbs. Most libraries have a fairly good selection and you can have the pages you need xeroxed. Also spend some time browsing in the red search function at the top of the page. Enter something like "rebuilding carbs" and you will probably get more than you care to read.<br /><br />On the wate-block stuff - what you describe your mechanic telling you makes no sense at all - to me at least. Have some one else give you a second opinion.

 

[roscoe]

Re: Mercury 65hp Thunderbolt Ignition... is screwed ;( Im no mechanic either

Sounds to me like you could have several different problems.<br /><br />One would be that the water tube, going from the water pump/impeller to the block, has broken, disconnected, or corroded through. Or that the water drain route has been clogged up, causing the water to fill the leg section.<br /><br />If the "motor bay" is filling as you say, the water is probably wreaking havoc with the wiring and plug wires. You can't expect to get a spark to the cylinder if the wire is grounding out in the water.<br /><br />One problem at a time. You will have to get the water flow right first. This includes checking the water passages in the block for any blockages , going into the lower leg and checking the plumbing, and checking the drain route in lower unit for any obstructions. You might as well change the water impeller while you have it apart, if you haven't done so recently.