Engine won't go beyond 3thou

[Mark.24]

Hi everyone,<br /><br />Engine: 1982, 3-cylinder, 70 HP Mercury with Thunderbolt ignition.<br /><br />Took the boat out on Saturday for a trial run following the installation of a new fuel pump gasket set, which included a modification comprising of a spring with cap to keep the diaphragm taut.<br /><br />The boat set off fine for the first two minutes but as the revs began to rise towards WOT, the engine started to back off down to 3,000 then 1,500rpm, until it gave up and stopped. The primer bulb was squeezed, she fired back up and limped along fluctuating between 1,500 and 2k with no desire to go beyond this. It also quit on me a couple of times heading back to the slipway. I did also notice that when the primer bulb was squeezed and you back off on the throttle slightly the rpm would rise by 2-300 rpm<br /><br />I’m considering removing the inline fuel filter attached to the engine for a straight through pipe from the fuel tank to the engine to see what difference that makes.<br /><br />Any advice is welcome, I believe it’s a fuel starvation problem unless you guys throw a different light onto it. Does anybody think that the reed valves maybe damaged?<br /><br />Cheers<br /><br />Mark

 

[rodbolt]

Re: Engine won't go beyond 3thou

hello<br /> as with all repairs start with a compression and spark test.<br /> just because it was good when ya left the dock doesnt mean it will be good when ya limp back. I doubt its a reed but it could be. sounds more like some trash in the lines made its way to the carbs. double check the last repair and do the basic trouble shooting.<br /> spark and compression. if ya got both look at the fuel system.<br /> if you run it with the filter removed buy carb kits. <br /> good luck and keep posting

 

[Mark.24]

Re: Engine won't go beyond 3thou

Thanks Rodbolt,<br /><br />I'll check the compression and sparks again, remove my fuel lines blast them with my compressor. I think following that I'll be looking at the carbs to check if they ingested something.<br /><br />Also, if you take the Teleflex steering cover plate away from the unit to re-grease, how do you put it back together by yourself! I did it last week and required an extra pair of hands<br /><br />Cheers<br /><br />Mark

 

[mellowyellow]

Re: Engine won't go beyond 3thou

squeeze primer bulb and see if gas leaks out of carb.<br />may be flooding from a stuck float???<br />good luck,<br />M.Y.

 

[Clams Canino]

Re: Engine won't go beyond 3thou

Hmm.....<br /><br />Perhaps you assembled the pump wrong? Or maybe that modification isn't all it's cracked up to be?<br /><br />Look to "what you've touched" 1st when troubleshooting.<br /><br />-W<br /><br />

Originally posted by Mark.24:<br />Hi everyone,<br /><br />Engine: 1982, 3-cylinder, 70 HP Mercury with Thunderbolt ignition.<br /><br />Took the boat out on Saturday for a trial run following the installation of a new fuel pump gasket set, which included a modification comprising of a spring with cap to keep the diaphragm taut.<br /><br />The boat set off fine for the first two minutes but as the revs began to rise towards WOT, the engine started to back off down to 3,000 then 1,500rpm, until it gave up and stopped. The primer bulb was squeezed, she fired back up and limped along fluctuating between 1,500 and 2k with no desire to go beyond this. It also quit on me a couple of times heading back to the slipway. I did also notice that when the primer bulb was squeezed and you back off on the throttle slightly the rpm would rise by 2-300 rpm<br /><br />I’m considering removing the inline fuel filter attached to the engine for a straight through pipe from the fuel tank to the engine to see what difference that makes.<br /><br />Any advice is welcome, I believe it’s a fuel starvation problem unless you guys throw a different light onto it. Does anybody think that the reed valves maybe damaged?<br /><br />Cheers<br /><br />Mark

 

[mellowyellow]

Re: Engine won't go beyond 3thou

good point CC, I had similar problem due to<br />wrong gasket on pump once....

 

[Mark.24]

Re: Engine won't go beyond 3thou

Thanks guys.<br /><br />I'll re-check the fuel pump diaghragm to be sure and I keep the old parts for reference. Might also remove that diaphragm spring<br />I'll also squeeze the primer bulb to see if fuel leaks. Plus I plan to individually do a comp test, check fuel lines, spark test, fuel filter, high + low stator test.<br />Maybe that will resolve it, if not carb re-build! Just hoping its not the reed valves. <br /><br />Once thats done, I've just got to wait for the tide

 

[Elmer Fudge]

Re: Engine won't go beyond 3thou

Also make sure that your fuel lines are air tight,and check the male and female connection where your fuel line connects to the motor.<br />oh! and make sure that the tank is venting properly

 

[Mark.24]

Re: Engine won't go beyond 3thou

Thanks for all your replys.<br /><br />I spent a few minutes over viewing my engine. Two areas of concern which need sorting.<br />1) The pipe attaching to the male connector near to the transom has a slightly large ID than the connector and is heavily kinked! <br />2) I forgot to replace a cable tie on a pipe which mates to the fuel pump . The pipe also has a 10mm slit, not sure if its penetrated the inner wall.<br />3) I've removed the spring modification which is suppose to keep the F. pump diaghragm taught<br /><br />Thanks once again guys <br />Mark