boggs at full throttle

[chesire_catt]

I have a 1986 140 mercruiser. It runs great but at full throttle it boggs down it sounds like it is running out of gas. I have changed the fuel filters, anti syphon valve, cleaned the carb, flame arrestor, changed the points, plugs, the problem doesn't happen all the time. but it still does happen. After I changed the anti-syphon valve the next time I took it out it ran great, until the end of the day. It was a cold day in the AM when i took it out low 40's and warmed up to about 65-70 in the afternoon maybe warmer. it started to act up on the way home. then Cleaned the carb good and put it back together, replaceing the inlet needle and seat. took it out yesterday and it was bogging again at 30-35 mph. was running a little better than before but still bogging. this time however it did run better when I squeezed the bulb, did not mak a difference in the past. <br /> The inlet needle and seat in the book show a spring but there was not one in the carb when I took it apart. (thats why I replaced it) and the new one didn't have one either. Book says something about changing float level if spring is not used (don't know what it is now, how to check, or how to change.) could this be my problem? <br />Fuel pump? how do I check. also one of the hoses from water filter is soft. I can squeeze together it is kinda oval shaped instead of round. I know I need to replace but could this be the problem. <br />Maybe when it was cold it was harder then when it warmed up it gave in under the high pressure? Does this sound possible? I really need to get this fixed the wife is gonna kill me soon she doesn't mind me spending but does mind it not being fixed please help I know it's a little long winded thanks

 

[chesire_catt]

Re: boggs at full throttle

Oh yea copression good on all cylinder 165 165 163 165. thanks again

 

[Cut n' Jump]

Re: boggs at full throttle

I'd replace all the fuel hoses starting with the ones before the fuel pump. They can suck shut easily if they are soft and have a small kink in them. I've seen hoses that leaked no fuel but sucked in air. Is the gas tank clean? Could there be a blockage in the fuel outlet of the tank? Try new hoses first and get marine approved heavy duty ones. Fuel hose is no place to skimp. Don't worry about the spring, it just keeps the float from bouncing around and 99% have been already tossed. I think its the laziness of carb rebuilders who know that spring won't make any difference. I throw them away too.

 

[DJ]

Re: boggs at full throttle

Cheshire,<br /><br />One thing you mentioned that caught my attention "squeeze the bulb". This is an I/O right? Never seen a primer bulb on an I/O!<br /><br />Agree with changing the hoses. It certainly won't hurt, not that expensive and can save you alot of grief in the long run. Let us know!

 

[petryshyn]

Re: boggs at full throttle

You gotta do a fuel pressure test. Until then, everything else is just speculation.<br />Borrow or buy a pressure gauge. Tee in just before the carb. Measure inlet pressure while running at WOT. (3.5 - 5.5psi is a generic spec.)If pressure is low, get back to us.<br /><br />Good luck...

 

[chesire]

Re: boggs at full throttle

Thanks all. I replaced the hose I was questioning but have not had a chance to get it in the water. I am going to do a fuel pressure check ASAP I have read many many posts that Schematic has added to and has hit the problem dead on. I did however run gas int a buck from just before the carb by cranking engine it caqme out in heavy pulses about 4 oz in 5 cranks. Hpefully I can get the boat out today and get some numbers for you thanks again.

 

[chesire]

Re: boggs at full throttle

and yes this is an I/O the bulb is in the line right after the water/fuel filter. I guess the previous owner (and only) owner installed it.

 

[Cut n' Jump]

Re: boggs at full throttle

I like running a clear plastic fuel filter on permanantly mounted fuel tanks on any motor without a fuel tank mounted fuel pump. It stops dirt and shows when yer outta gas. I'm leery about putting one on my o/b because my fuel tanks are portable 6 gal units and those plastic filters don't take kindly to being tossed and tugged on.

 

[chesire]

Re: boggs at full throttle

OK so I took it out and ran for a bit ran a little better (with new hose 35MPH 4400rpm before bogging 4600max did not get a chance to run a pressure check. Soon I promise. I do have a question my choke started closing on my never did before. what could cause this? also is it possible to have 2 fuel pumps or can you tell me what the object is that the fuel runs through after the water filter (its a cylinder shaped and has power to it. sorry I must sound like an idiot but, well I am. Do you change the filter on the water filter. I have tried to get it off doesn't want to come off so I didn't think about it anymore. Thanks a million hopefully I'll be Dolphin fishing this weekend Mahi Mahi my house!!!

 

[chesire]

Re: boggs at full throttle

OK so I took it out and ran for a bit ran a little better (with new hose 35MPH 4400rpm before bogging 4600max did not get a chance to run a pressure check. Soon I promise. I do have a question my choke started closing on my never did before. what could cause this? also is it possible to have 2 fuel pumps or can you tell me what the object is that the fuel runs through after the water filter (its a cylinder shaped and has power to it. sorry I must sound like an idiot but, well I am. Do you change the filter on the water filter. I have tried to get it off doesn't want to come off so I didn't think about it anymore. Thanks a million hopefully I'll be Dolphin fishing this weekend Mahi Mahi my house!!!

 

[chesire]

Re: boggs at full throttle

OK so I took it out and ran for a bit ran a little better (with new hose 35MPH 4400rpm before bogging 4600max did not get a chance to run a pressure check. Soon I promise. I do have a question my choke started closing on my never did before. what could cause this? also is it possible to have 2 fuel pumps or can you tell me what the object is that the fuel runs through after the water filter (its a cylinder shaped and has power to it. sorry I must sound like an idiot but, well I am. Do you change the filter on the water filter. I have tried to get it off doesn't want to come off so I didn't think about it anymore. Thanks a million hopefully I'll be Dolphin fishing this weekend Mahi Mahi my house!!!

 

[chesire_catt]

Re: boggs at full throttle

I know I am not too mechanically educated but, but I am a quick learner. Please bear with me. Had my neighbor look at fuel system tonight and he thinks I have 2 fuel pumps also. How can this be, and why? Is one for the water fuel separator. Doel the filter on the water/ fuel separator get changed? I can get a picture if I am way off course here someone please help.

 

[chesire]

Re: boggs at full throttle

OK OK so I must be asking some really dumb questions or getting on everyone's nerves, or both. please bear with me. This is my first boat. many things are different between my car motor and the boat motor. I did get the fuel/water filter changed. Boy was it stuck I had to remove the whole unit put the fiter in a bench vise and use a prybar and a hammer to get it off./ man was it filthy some water and a bunch of red shtuff (varnish?) the filter that was on there was the wrong one for my engine it was for an outboard (does that make much of a difference?)why two fuel pumps?is this normal? the electric one has a short some where It works when I hook it up direct but not when i turn the key so I will fix that, but should I keep 2 fuel pumps? Someone please answer me I'm not really an Idiot I just play one on the the Web. thanks a million

 

[chesire]

Re: boggs at full throttle

OK so I may be an idiot after all!!!! but everyone has to start some where I have learned alot in the past few months. I think I can even change my own oil now! Just kidding. after changing the water/fuel filter and hooking up the second fuel pump itrs running great. just missing a little at top end. I think it is due to improper point gap. I am going to set with a dwell meter tomorrow. lol It is printed on the filter to change once a year or when engine slows. errrrrrrrr I feel dumb. Oh well just remember if it weren't for people like me you guys wouldn't look so smart!<br />The thing that gets ms is I really should have know better. well thanks to all of your help and this board its a life saver!<br />I'm sure I'll be posting more ?s in the future. thanks in advance. <br /><br />KISS Keep it simple Stupid!

 

[chesire]

Re: boggs at full throttle

OK so I may be an idiot after all!!!! but everyone has to start some where I have learned alot in the past few months. I think I can even change my own oil now! Just kidding. after changing the water/fuel filter and hooking up the second fuel pump itrs running great. just missing a little at top end. I think it is due to improper point gap. I am going to set with a dwell meter tomorrow. lol It is printed on the filter to change once a year or when engine slows. errrrrrrrr I feel dumb. Oh well just remember if it weren't for people like me you guys wouldn't look so smart!<br />The thing that gets ms is I really should have know better. well thanks to all of your help and this board its a life saver!<br />I'm sure I'll be posting more ?s in the future. thanks in advance. <br /><br />KISS Keep it simple Stupid!