Hesitation Question

[jaymasta]

hey guys I have a mid 70s, 650 on a 14ft sportsman, and I took it out today for the first time, ran great for the first 15 minutes or so took out into the middle of the lake and killed it and then ate a sandwhich, I then fired it back up and when I apply the throttle it goes to about 2000rpm and then bogs as I give it more throttle and eventually stalls, I played around with it for almost an hour and could not get it to go over 2000rpm no matter what i did, although if it is in neutral and I use fast idle it will freely go up to 5000+... So i chugged it back to the boat launch took it out of the water then went back in about 2 hours later to see if waiting for it to cool down made a diference and it didn't, same thing right off the bat, coudn't get it over 2000rpm, and it would bog and eventually just die, in neutral i can still get it up over 5000 no problem... so right now I have sprayed it with deep creep, dumped out all the old gas(don't know how long it was in there for) and filled it with new gas and put seafoam in the new gas/oil mix, and tomorow I will check the plugs and wires but they look brand new from the outside...any other tips for me or anything I should look at tomorow....this is strange becuase in neutral I can rev it no problem just in gear it won't go over 2000

 

[urbanp]

Re: Hesitation Question


Pull off the distributor cap, make sure there is still good spring action with the centre pin, If you have an ohm meter, check the resistance in your wires, they should be fairly low (this will vary depending on wire length brand and condition...) If they are over 10k Ohm you probably have bad wires. If you have a compression tester, check your compression. It's always nice to know if you comression is good or not, and if you have a factory manual you can use for tuning your carbs, then you might want to do this. Also Check timing. Most people in this forum seem to like the factory merc manuals the best. (More detailed, more accurate, no goofy specs, and model specific)


Happy boatingd

 

[Texasmark]

Re: Hesitation Question

Fuel starvation. Under load requires more fuel and apparently you aren't getting it.

Must have a clogged fuel filter from that old gas. Old gas (at least used to) turns to varnish and acts just like the varnish you use to preserve wood. On mesh fuel filters it just seals them right up.

Or you picked up some crud from the tank which is partially clogging your fuel system. Or the diaphragm in the fuel pump may be damaged from old age.

One test is to squeeze the bulb when the engine boggs and see if it improves. If so the above is your problem.

Mark
One place to check is the

 

[jaymasta]

Re: Hesitation Question

Fuel starvation. Under load requires more fuel and apparently you aren't getting it.

Must have a clogged fuel filter from that old gas. Old gas (at least used to) turns to varnish and acts just like the varnish you use to preserve wood. On mesh fuel filters it just seals them right up.

Or you picked up some crud from the tank which is partially clogging your fuel system. Or the diaphragm in the fuel pump may be damaged from old age.

One test is to squeeze the bulb when the engine boggs and see if it improves. If so the above is your problem.

Mark
One place to check is the

would pressing the choke button solve this problem, because i tried pushing it while running and it just stalled it instantly, anyways tomorow I will try pressing the bulb, and checking the fuel filter, Iam not sure where it is on this engine, do you guys have any idea where it is or what to look for, and will sea foam in my gas tank clear anything partially blocking my fuel lines if that is the problem?

 

[fishingdan]

Re: Hesitation Question

FYI...don't rev it in neutral. It can only cause damage and really doesn't tell you anything. With no load on the engine, it will redline even if isn't running on all cylinders.

 

[jaymasta]

Re: Hesitation Question

FYI...don't rev it in neutral. It can only cause damage and really doesn't tell you anything. With no load on the engine, it will redline even if isn't running on all cylinders.

generally I don't, but I did this time to see if I could get it to go beyond 2000rpm in neutral in which case it did.

 

[tashasdaddy]

Re: Hesitation Question

have you done a compression test?

 

[Texasmark]

Re: Hesitation Question

If you pushed the choke button and it died, it says to me that you flooded it which says that fuel starvation is not your problem.

Every time I have hit the choke (fuel enrichment) button with the engine running was while trying to get started and I got an improvement in rpm's.....apparently because I was fuel starved.

HTH

Mark

 

[jaymasta]

Re: Hesitation Question

ok so obviously it has something to do with fuel, I did a full carb cleaning today with deep creep and seafoam in the gas, and basically If i give the bulb a few pumps while iam at 2000rpm and play with the throttle, it goes, and once Iam above 2000rpm It has no problem staying above 2000rpm and going WOT, but as soon as I get it below 2000rpm I can't get it back over it without pumping the bulb and playing with the throttle at the same time, Iam assuming it has a pinhole leak somewhere and for some reason once I get it going there is enough fuel suction that it overcomes the hole but bellow that it just doesn't cut it or somthing Iam a little confused I will be checking all the fuel lines etc tomorow, could it be the fuel pump,? anyone have any other ideas?

 

[akita8]

Re: Hesitation Question

Definately do a compression check on it before you do a bunch of troubleshooting! I had the same problem and after fuel system and ignition system troubleshooting I found a cylinder with ZERO compression.

 

[jaymasta]

Re: Hesitation Question

Definately do a compression check on it before you do a bunch of troubleshooting! I had the same problem and after fuel system and ignition system troubleshooting I found a cylinder with ZERO compression.

120, 125, 130 or approximatly, I don't think it is a compression problem because it fires up right away with no choke or anything, idles find, has good power, and sounds great, it just won't go over 2000rpm unless I give the bulb couple squeezes to help it along...

 

[swist]

Re: Hesitation Question

Sounds like a carb problem. Running lean. Will start and idle OK. If you can get it to accelerate to higher speeds, will probably run well, but will bog and/or stall as you try to accelerate. No-load performance is irrelevant.

This match your symptoms, if so get your carbs rebuilt.

 

[jaymasta]

Re: Hesitation Question

Sounds like a carb problem. Running lean. Will start and idle OK. If you can get it to accelerate to higher speeds, will probably run well, but will bog and/or stall as you try to accelerate. No-load performance is irrelevant.

This match your symptoms, if so get your carbs rebuilt.

that exactly matchs my symtoms, the only way for me to get it to higher speeds is to get the motor at 2000rpm, and then to give the bulb 2 or 3 sqeezes and then jump back to the front and give it full throttle and then it jumps right up like nothing is wrong, and as long as I keep it above 2000rpm I am fine.. I belive it might be a carb prob as well, is there anything I can do to verify this, or do these symtoms pretty much designate that? if so how hard are the carbs to remove and rebuild, Iam fairly mechanically inclined, although I have never rebuilt a carb before, how much are rebuild kits also, I assume oldmercs might be able to help me out?

 

[timmathis]

Re: Hesitation Question

You could have a clogged pick up in the tank or fuel pump bad. Hole in line Etc. Check the system all over. Probably a good idea to pull carbs and clean also.
Tim

 

[jaymasta]

Re: Hesitation Question

You could have a clogged pick up in the tank or fuel pump bad. Hole in line Etc. Check the system all over. Probably a good idea to pull carbs and clean also.
Tim

i think there is an extremely tiny hole in my bulb somewhere, there is always a tiny bit of gas on it but i can pump it up until its tight and I don't see anything squirting out.

 

[studlymandingo]

Re: Hesitation Question

Replace the bulb first. If it still does the same thing, rebuild the fuel pump, still doing it, replace all of the fuel line. If you get more RPMs by pumping the bulb, you aren't getting enough fuel.

 

[timmathis]

Re: Hesitation Question

Get a good bulb and fuel line. Some of the aftermarket ones suck.

 

[zoltang]

Re: Hesitation Question

i dont know if this is stupid but o well, iv had this same problem that i can run the engine at high rpms and then suddenly the engine dies down then i pump the bulb and it jumps back up then worked for a little while until i couldn't squeeze the bulb cuz i was already flatened....turns out the problem was i forgot to loosen the cap on the gas tank becuse it couldnt get air.....stupid i know...damn memory....good luck with your problem

 

[timmathis]

Re: Hesitation Question

Yes it must be vented also.

 

[swist]

Re: Hesitation Question

You guys are all dancing around the problem. He has good fuel flow at high rpm, that eliminates blockages, fuel pump, bulb, etc. He needs a carb cleaning and/or rebuild. His symptoms are exactly that of lean idle.