Dont know what to do??

[70Silverline]

i have a 1970 silverline comareo thats 16 and 1/2 feet POWERED BY A 250 CUBIC INCH INLINE CHEVY/MERCRUISER V6 it ran fine yester day for 20 min's at WOP in the water and today when we put it in NOTING THIS IS THE SECOND TIME OUT IN 2 YRS it started popping from the carb after 2 miles at almost WOP then it bogged way down and would only run about 5 mph after i backed off a little bit it cut off and would not restart seems to pop from the carb like a backfire when i try to start it the temp was fine trim was fine oil pressure was fine and the rpms never went over 4500 at wop so i dont know what to check it was just in the shop having the POINTS,CONDENSER,ROTOR BUTTON,DISTRIBUTOR CAP,WIRES,and finally PLUGS replaced then when i got it hom i replaced the coil so all the electric stuff was replaced WHAT DO I NEED TO CHECK NOW oh by the way it WIL NOT restart well not in the water anyway i havnt tried at home when its cold yet????? PLEASE HELP MY FAMILY IS GOING NUTS WITHOUT OUR BOAT???

 

[Alumarine]

Re: Dont know what to do??

Welcome.

If you use some punctuation and perhaps a paragraph or two, someone might be able to help you.

 

[Bondo]

Re: Dont know what to do??

Ayuh,.... Sounds like a Fuel Delivery issue to me....

Could be anything, or everything between the fueltank vent to the Carb....

I'd start with changing the Fuel Filters....
Should be 1 in the Carb,+ another in the Fuel Pump....

Welcome.

If you use some punctuation and perhaps a paragraph or two, someone might be able to help you.

Ayuh,... What he said,... And,.. No reason for the Cap-lock either...

 

[70Silverline]

Re: Dont know what to do??

i did look into the carb while i wa out on the water today broken down and i saw 2 squirts of fuel with no problems at all it semed to be getting plenty of fuel i talked to someone i know who owns tons of boats and he seems to think the motor i blown but it was attempting to restart just backfiring through the carb could the motor be blown? i ran a compression check on it righ before going out all was great? thanks for the help by the way!!

 

[Bondo]

Re: Dont know what to do??

i ran a compression check on it righ before going out all was great?

Ayuh,... Probably time for Another 1.....

 

[Gary H NC]

Re: Dont know what to do??

How old is the fuel and was Stabil used in it over the winter...?
Could just be bad gas..

 

[70Silverline]

Re: Dont know what to do??

fuel was drained from entire system and it stayed winterized tank was thoroughly cleaned and it was all brand new gas from the pump today

 

[70Silverline]

Re: Dont know what to do??

how do i check the timing never done that before?

 

[CheapboatKev]

Re: Dont know what to do??

Am I ignorant..but never heard of an inline-V6...Would have to be staggered or doesn't exist....?!?

 

[coastalcruiser]

Re: Dont know what to do??

You need a timing light and a manual there is a free manual at the top of Mercruiser, OMC, Volvo & other I/O & Inboard Engines & Outdrives
The engine must be running, you take the light and point it at the notch on the flywheel. Rotate the distributor until the mark lines up with the line. The manual will give you the specifications for your engine.
Don't forget to change the points and set the dwell.

 

[picklenjim]

Re: Dont know what to do??

I would take it back to the mechanic that just replaced all the ignition parts.He should have,and may have, set the timing when he replaced all those parts.

 

[Surfdancer]

Re: Dont know what to do??

It takes 3 things for an engine to run, and run correctly.

1. A fuel/air mixture
2. A source of ignition
3. Controlled compression

Troubleshooting is a process of elimination based on clues. No power and popping through the carb? Based on the comment of a recent tune up, I would start with the ignition.

If the points were changed, it is possible that after running (when things get warm), then shutting off until the next outing (when things get cool), the point retention screws lost some of their grip. If the engine runs, check the dwell - that will be a sure indicator of incorrect gap, or eroded points.

If the ignition checks out, move on to the fuel/air system. Check filters, fuel quality, sediment in the carburetor fuel bowl, etc. Don't make any adjustments until you know you have a reliable supply of clean fuel going to the control passages (jets, mixture circuits, etc) in the carb.

If the fuel system looks okay, move on to compression. Perform a compression check - some junk on pistons or valves (carbon) may have developed and moved. Or a worn cam chain may have jumped a tooth on the sprockets. A compression check is an easy way to assess if the engine is in good shape.

Another way to evaluate the engines health is with a vacuum gauge on the intake manifold. There is a link in one of the sticky's that provides a good discussion on using a vacuum gauge for diagnostics.

I always use the KISS theory and start with the simple and stupid stuff. Based on what you said, I would pull the distributor cap and check for moisture and the point condition (gap and contact condition).

 

[Silvertip]

Re: Dont know what to do??

The engine doesn't have to be running to check dwell. A dwell meter will read running on the starter. A feeler gauge is also a replacement for the dwell meter. That at least gets you in the ball park. Even a match book cover gets point gap close enough to run. I too suspect fuel delivery such as a slug of water from the tank sitting empty during long period of storage. And the possiblity that a new tank of fuel stirred up some crud that is now sitting in the fuel filter. Ignition timing doesn't generally change unless something came loose. Since only the points were changed, and it ran fine for a bit, I don't think that's the problem. Replacing the coil with the wrong type may be the issue so checking for spark on all cylinders is a good starting point. As for the inline 250 CI V6 --yup, you have an inline six, not a v6. Can't have it both ways on the same engine.

 

[70Silverline]

Re: Dont know what to do??

Thank you for all the replys tommorow is the start of my search im gonna first run a compression check i was told today by a A + marine mechanic in the area very familiar with these engines that it may have run lean due to sitting and not cleaning the carbs and burnt the valves so he wants me to check compression and do leak down test, Then i think im gonna check for all my spark if the leak down and compression checks out fine and if i get all my spark im gonna go to the carb and fuel line issues it sat for almost 2 yrs with no use and we never had carb cleaned however it ran fine like a dream for 2 miles that is until maybe some gunk got up into the parts of the carb that need to be totally cleaned but im leaning toward burnt up valves and maybe a overhaul which is ok i will just trade it in on a new one and say goodbye to old faithful by the way her name was KICKN BASS now she was renamed to AINT KICKN CH** lol again thanks for all the replys and help

to recap yes it is a Chevrolet engine made by mercruiser in the 70's for marine use no its not a V6 i didnt mean to say that sorry everyone!!

 

[HT32BSX115]

Re: Dont know what to do??

no its not a V6 i didnt mean to say that sorry everyone!!

You just have to watch it!!!! It's a pretty rough crowd here!!

 

[70Silverline]

Re: Dont know what to do??

figured out the problems there are 2 problems went back to my very good mechanic and the first thing we noticed together is i have a cracked spark plug it was cracked near the top so we are guessing its a manufacturing process flaw and second is the carb needs a rebuild its dumping raw fuel like crazy starving the motor of air and running extra extra lean causing to burn hotter and star to sieze the motor which never hapned cuz it runs just fine now but a little rough due to the carb problem and also some idiot put a heater hose on the wet hose assembly on the lower unit to bring water from the lower unit to the motor which when the lower unit is lowered it kinks causing very little water to get to the engine so all in a nut shell it was bieng starved of water and air and burning hot as all get out so basically almost burnt it up if i wouldnt have shut it down it would have siezed so about 350 bucks and im back and running which includes carb rebuild and rejet and setting and replace bellows on lower unit and all hoses on lower unit and motor due to dry rot replace wires and 1 spark plug due to the rest bieng brand new and i should be good for the year THANKS EVERYONE FOR ALL YOUR HELP!!!

 

[ziggy]

Re: Dont know what to do??

hum, so ya've worked on the electrical, ya've worked on the carb. yer gonna work on the cooling system. you have to much fuel and are running lean. in this thread i see it all over the place. random parts replacement even... i think ya should start with a compression test. http://www.boatfix.com/merc/Bullet/97/97_25.pdf do it correctly. ya might even post up the results. then move to the electrical. don't just put parts on it. go by the book and set the sparkpug gap, dwell, timing to spec. make sure ya got the proper coil. there's differences i believe from one to the other. the carb. could be the problem, but leave it for last, after all else fails. includeing doing some fuel system checks. like fuel pump pressure, good fuel, antisiphone valve, fuel filters, etc.
this is a pretty good thread here. http://forums.iboats.com/showthread.php?t=302462. if you rebuild the carb. do it by the book too and set up the few adj. that are nessesary. after you soak it in carb cleaner and use compressed air to blow all the small holes on it.

i think you need a plan... + use the oem service manual. good luck with your project...