1976 Mercury 650 Thunderbolt Stalling

[Riddler1100]

Hi, was just wondering if anyone could help me with a problem i am experiencing. I took my boat for a cruise on the river to keep it lubed and running, i had it going on full throttle (well just a fraction back from full throttle) for approx 1 Hour just running up and down the river, the only time i backed off was when i was manouvering around a sweeping u-turn to head back the other way. I stopped the motor out in the middle (after about an hour of trouble free pleasure, motor did not even miss a beat or anything couldnt have been happier) and re-started it with absolute no problem idled perfectly, but when i put it in forward gear to take off again, it bogged down and lost power to the point where it stalled. i re-started the motor to which it idled perfectly but once again it wouldnt let me put it under power, would only let me slowly troll with throttle approx 2 inches forward of neutral. So my question is does anyone know what this possibly could be, i thought it was carbie, i have added a carbie cleaner fuel additive to the fuel to try and "clean' any foreign material "if any". Would love to get this boat up and going for the Christams Holidays. PS: Had it running perfectly last Christmas fishing/tubing had a ball, but on this instance i had it at full throttle returning from fishing and it bogged down and stalled under power, it would only idle after i engaged the idle lever. Cleaned spark plugs and put fresh fuel in tank, but still have the symptons as above when i took it to the river.

Please Help

Thanks

Matt

 

[ENSIGN]

Re: 1976 Mercury 650 Thunderbolt Stalling

Try running the boat on a portable gas tank,We have done this many times at the shop and will at least isolate the motor from the boat. If the gas in your tank is old or contaminated you should pump it out.

 

[Skydive80]

Re: 1976 Mercury 650 Thunderbolt Stalling

Just a shot in the dark as I am just starting to learn about boat motors, but it sounds like a problem a friend had. If you have a primer bulb, check to make sure the bulb is not collapsing when you increase the throttle. Friend found out that due to the ethanols in gas, if you let the gas sit in the bulb for awhile it will slowly wear down the inside structure.
As I said, just a shot in the dark but hope it helps. I have a 1969 Merc 650 I am just starting to rebuild.
Good luck.
Skydive80

 

[rabeck5792]

Re: 1976 Mercury 650 Thunderbolt Stalling

it could be heat soak.thats when the fuel boils in the carbs & evaporates.to check this run the engine the same way,shut it down for half of an hour,when it does this,prime the bulb.if it takes off & runs ok,then you have heat soak.

 

[superwooter]

Re: 1976 Mercury 650 Thunderbolt Stalling

rabeck,
what is (technically speaking) happening if your engine is experiencing heat soak? what causes the fuel to boil? also, what do you do to prevent it from happening? i'd ljust like more info on this.
thanks,
wooter

 

[Skydive80]

Re: 1976 Mercury 650 Thunderbolt Stalling

Here is a good link that explains heat soak and the problems of using ethanol gas in older boat motors.

http://www.used-boats-canada.ca/item/ethanol-blended-fuel-and-boat-engines

Hope this helps,
Skydive80

 

[Riddler1100]

Re: 1976 Mercury 650 Thunderbolt Stalling

Thanks guys, sorry for the late reply as i have been away for work.

This "Heat Soak" which i have not heard of until now seems like it could be the problem, as the motor would be getting hot and as such yes could be evaporating the fuel in the hoses prior to the carbies.

Thanks again guys and i'll keep you informed on any further problems or resolving

First Boat, First motor so once again thanks very much

Matt

 

[Dotong]

Re: 1976 Mercury 650 Thunderbolt Stalling

hi, something similer happened to my 650 and it turned out that the spark plugs were shorting off the cowling, not enough to cause a stall untill you engage gear and you get that bit of resistance on the engine. if you try running the outboard without the cowling and it works fine you will know that this is it. dont do what i did to find out and touch the dodgy ht lead and get a heck of a shock!!!!

cheers

 

[Riddler1100]

Re: 1976 Mercury 650 Thunderbolt Stalling

Thanks Botong,

I'll try that also as my gut feeling does tell me that its more electrical or alike than carbie problem, as it runs very well for an hour or so. Could you put a foam piece or alike inside the cowling directly behind the spark plugs?? so as it cant short out on the cowling?? Sorry im new to this as i generally work on motorbikes but have never had the glory or chance to work on a marine engine.

Thanks

Matt

 

[wolverine13]

Re: 1976 Mercury 650 Thunderbolt Stalling

Hey guys,
I'm was just killing some time on here and found out that there are a lot of people dealing with the same issues as me. I know very little about boats, but I'm a quick learner. I have a merc 650 of an unknown year on my boat and it runs like a champ in the driveway and when I first start it by the boat ramp, but after it is warm, it either has trouble starting, or stalls out as soon as I get it in gear (it idles fine and can rev up the throttle without problem as long as it's not in gear). I can eventually get it going, but I usually go through 3-6 bouts of it stalling out before it will finally take off (and only take off when I basically jam it into gear and right to full throttle). All of the weekend "boat mechanics" that i talk to say it sounds like anything from carb problems to points, fuel pumps, plugs + wires, the list goes on. If anyone has successfully solved this problem, I would really appreciate a little advice on the best place to start. Also, what is a cowling? that sounds very similar to what my boat is doing.
Thanks, Joel

 

[richard kirkland]

Re: 1976 Mercury 650 Thunderbolt Stalling

Hi, I am in australia and have a 1974 Merc 650 Blueband. I was having trouble with my motor going from idle and into gear, i found another user online who emailed me an electronic manual and in there it tells you how to setup the linkage which controls throttle and idle. DO THIS WITHOUT RUNNING ENGINE When you take off the engine housing check out the black circular linkage which is attached to the throttle cable, have another person work the gear/throttle control, engage forward gear and you should see the linkage advance towards the front of the motor, push the lever all the way forward and you will see the linkage move and the dizzy cap will advance also, make sure this linkage is tight and that someone has not adjusted the throttle stops. email me and i can send you a copy of the manual for the 65hp blue band. Also i found the motor hard to start after a long rest while fishing, a few pumps of the fuel bulb prior to running always helped and before i got under way i would run the motor for a few mins to get warm again. When you sit fishing for hours the petrol basically evaporates from the carbs. Also make sure the vent screw on top of your fuel tank is open prior to running, this allows the fuel to be sucked up by the pump, if this is closed the engine will starve of fuel and die.

Also on the sie of the motor near to the starter motor you will find a tilt switch mounted at an angle, this is connected to earth and to the switch box, it is fitted just incase your motor is attempted to start whilst in the tilted position.Remove this mercury tilt switch as I am sure you would not be inclined to start the motor in tilt.The tilt switches can sometimes play up causing the motor to stall for no reason.

My best advice is to find a decent boat mechanic and have your motor checked out fully, after all you are relying on it when on the water!

happy boating

rich k

 

[richard kirkland]

Re: 1976 Mercury 650 Thunderbolt Stalling

UPDATE

Hi, I just found an old link to a guy in USA who made a website about his rebuild of a blueband 650. http://www.zmicro.net/

hope this helps

the electronic manual is 400mb so not easy to email in one go, i might have to break it down into sections.

rich k

 

[richard kirkland]

Re: 1976 Mercury 650 Thunderbolt Stalling

another update

anyone wanting to download the 400mb manual please follow this link....This covers the 650 amongst others of course

http://www.myoutboardengine.com/file/

 

[crem1]

Re: 1976 Mercury 650 Thunderbolt Stalling

Either play with the carburator adjustments or take the carbs off and do a thorough cleaning in an organic solvent for a day. Buy a carb kit and replace pertinent parts. Re-install the carbs

 

[wolverine13]

Re: 1976 Mercury 650 Thunderbolt Stalling

Alright, thanks for the ideas. Unfortunately I will not be able to work on it until spring, but I have a better idea of where to start. Does anyone know where to get a carb rebuild without paying marina prices?
Joel

 

[crem1]

Re: 1976 Mercury 650 Thunderbolt Stalling

Try this one, it deals with older MERC's


http://jetes.wgurh.servertrust.com

 

[avenger79]

Re: 1976 Mercury 650 Thunderbolt Stalling

Alright, thanks for the ideas. Unfortunately I will not be able to work on it until spring, but I have a better idea of where to start. Does anyone know where to get a carb rebuild without paying marina prices?
Joel

sounds like you have my motor on your boat. mine does the exact thing that your's does. it runs alright as long as you keep going. if you stop for any length of time it takes forever to get going again. you can find the carb kits on iboats i think. do a search online also.

BTW i had my carbs and fuel pumps rebuilt and that was when this issue started. i think it's more a setting type thing. too lean, too rich, too advanced or something.

 

[abarron]

Re: 1976 Mercury 650 Thunderbolt Stalling

I have a 1974 850 85hp, my motor doe's something like that,It run good at all speeds but full speed,I bring it up to full speed it will run there for a few seconds and then bogs down and quits,But it will start right back. Any sugestions?

 

[oldmanfaw]

Re: 1976 Mercury 650 Thunderbolt Stalling

Hi, was just wondering if anyone could help me with a problem i am experiencing. I took my boat for a cruise on the river to keep it lubed and running, i had it going on full throttle (well just a fraction back from full throttle) for approx 1 Hour just running up and down the river, the only time i backed off was when i was manouvering around a sweeping u-turn to head back the other way. I stopped the motor out in the middle (after about an hour of trouble free pleasure, motor did not even miss a beat or anything couldnt have been happier) and re-started it with absolute no problem idled perfectly, but when i put it in forward gear to take off again, it bogged down and lost power to the point where it stalled. i re-started the motor to which it idled perfectly but once again it wouldnt let me put it under power, would only let me slowly troll with throttle approx 2 inches forward of neutral. So my question is does anyone know what this possibly could be, i thought it was carbie, i have added a carbie cleaner fuel additive to the fuel to try and "clean' any foreign material "if any". Would love to get this boat up and going for the Christams Holidays. PS: Had it running perfectly last Christmas fishing/tubing had a ball, but on this instance i had it at full throttle returning from fishing and it bogged down and stalled under power, it would only idle after i engaged the idle lever. Cleaned spark plugs and put fresh fuel in tank, but still have the symptons as above when i took it to the river.

Please Help

Thanks

Matt

check to see if throttle opens up the carb butterflies all the way if not disconect throttle cable and move throttle butterflies by hand if butterflies dont open all the way check excelerator pump could of come apart