Mercr 2.5L loss of power on acceleration

[horndog]

As stated above its a 2.5L merc with a 2-bbl rochester carb and i took her out for a ride and idles fine and runs great in neutral.<br /><br />When you accelerate under load, she bogs down and she dies, but in at low speed, barely above idle she is fine.<br /><br />I was thinking it was an accelerator pump, but didn't know if I would have to tear down the carb if its not necessary.<br /><br />any other ideas?

 

[DJ]

Re: Mercr 2.5L loss of power on acceleration

horndog,<br /><br />You can easily check the accelerator pump.<br /><br />IT IS BEST TO DO THIS WITH THE ENGINE OFF!<br /><br />Remove the spark arrestor (air cleaner) and look down into the carb throat while actuating the throttle. You should see a squirt of fuel each time you "goose" the throttle.<br /><br />Timing-Hook up a timing light and watch the advance of the timing as you accelerate the engine. Mechanical advance springs often break or stick. They are located under the breaker plate in the distributor.

 

[horndog]

Re: Mercr 2.5L loss of power on acceleration

based on the symptoms do you possibly think its the accelerator pump?

 

[DJ]

Re: Mercr 2.5L loss of power on acceleration

horndog,<br /><br />Based upon you description, I would say it's one or the other.<br /><br />What does it do if you try to accelerate very slowly, yet evenly?

 

[horndog]

Re: Mercr 2.5L loss of power on acceleration

it dies. You have to "feather" the throttle to get it going, but once its at WOT it is fine and runs like a champ

 

[DJ]

Re: Mercr 2.5L loss of power on acceleration

horndog,<br /><br />It still could be either. I would say that if "pumping" the throttle helps, your accel. pump is weak or out of adjustment.<br /><br />Both are relatively easy to check.

 

[horndog]

Re: Mercr 2.5L loss of power on acceleration

ok, I will take a look at it... Also at the marina they said it could be a bad float alignment? I didn't know those carbs were that touchy.

 

[horndog]

Re: Mercr 2.5L loss of power on acceleration

Replaced accelerator pump, VOILA! purrs like a kitten, and runs STRONG!

 

[horndog]

Re: Mercr 2.5L loss of power on acceleration

The bogging is not as noticiable since the acceleration pump has been fixed, but It is still rearing its ugly head.<br /><br />If I go from just being in gear and then open her up she wants to die. What could be the cause? But if I back off the throttle a bit and accelerate very slowly its fine. <br /><br />Now at WOT, I hear a ticking sound in the motor. Could this be the cause of the timing being off?

 

[Bondo]

Re: Mercr 2.5L loss of power on acceleration

Sounds to Me that You'd Better give that old war horse a Full,+ Complete Tune-Up..... While you Still have a Motor to Work On.....<br />With the motor running Lean, from fuel/carb issues... And the Ignition In Question..... Your Headed for a Melt-Down......

 

[horndog]

Re: Mercr 2.5L loss of power on acceleration

so do you think its the timing? I asked my father and he said "its old its going to make noises."<br /><br />Maybe because he is old and he makes noises that means everything that is old should?

 

[horndog]

Re: Mercr 2.5L loss of power on acceleration

could it be the timing? Should I check the manifold as well and see if its plugged?

 

[horndog]

Re: Mercr 2.5L loss of power on acceleration

ok... accelerator pump supposedly went bad, so had it replaced. ran it on the muffs and ran fine. put it in the water ran like a dog upon acceleration. <br /><br />if you put it in gear and hammer it will want to sputter and die, but if you put it in gear and accelerate SLOWLY to about 1500rpms she is ok then nail it. <br /><br />I replaced the plugs with some NGKs and set the timing, but not sure if the #1 cylinder was at TDC to set at 0, so I marked it as close as I could get the piston to the top. <br /><br />After all that, I put her in the lake and see how she performs, still better than before, but not as good as it should be. I also replaced the fuel filters in the carb and the fuel pump. <br /><br />What else could it be? plugged manifold exhaust port?

 

[bernieb]

Re: Mercr 2.5L loss of power on acceleration

This sounds similar to the problem like I'm having with my chev 350 and the last time out I had an auto mechanic along and as he looked down the rochester 4 barrel throats as I nailed it home he said gas spray reversed as I got the big studder out of the engine like it was going to stall.He told me to pull the heads and have them checked at the machine shop.He told me I may have a worn cam lobe that is not allowing the intake valve to open enough to allow gas to get in.My engine runs fine if I take it easy up to when the other two barrels are suppose to kick in.

 

[horndog]

Re: Mercr 2.5L loss of power on acceleration

yes, mine runs fine if you take it easy accelerating, but anything more, she coughs and dies. <br /><br />I thought it was odd that the accelerator pump was replaced twice and it still crapped out. I will call the mechanic on monday and see what he says.<br /><br />Did you end up fixing it or leaving it? Did you get any quotes for it? If so, how much were they looking to charge you for it

 

[bernieb]

Re: Mercr 2.5L loss of power on acceleration

Horndog my boat a 21foot sonic and the 350 they tell me is a late 60's with points and all ,but had been a real screamer as I am a "I'll fix it kind of guy"I attempt my own repairs although I'm not the best mechanic around but I do know some pros.When I get back to florida I'm taking a chain pulley and backing under a tree and pull the engine ,I'm taking the heads to Napa at the machine shop and see what he says,then I'll find out what I have to do to check the cam out while still in the block.It's strange how first you have to have problems before you learn anything. I pulled the engine up about 2 feet using 2x4's in a tri-pod configuration using chain at the top to change the starter this winter. As far as cost goes for yours .....get a price .I admire your name .I'm 66 ,I should change it to ground inspector.

 

[horndog]

Re: Mercr 2.5L loss of power on acceleration

bernie,<br /><br />where in florida do you live? I will be moving to tampa area in july/august. I could probably live with the problem now. Sure, I know how to take things apart, putting them back together is the problem <br /><br />I am still going to call the mechanic tomorrow and see what he says.

 

[bernieb]

Re: Mercr 2.5L loss of power on acceleration

Cedar Key Florida ......Stop by and we'll go out for some reel screaming king fish.Rainbow campground.My boat named two grand. I love my wife....but I love my boat a Hell've lot more.

 

[horndog]

Re: Mercr 2.5L loss of power on acceleration

hmm... I will probably take you up on that since I know absolutely jack sh*t about saltwater fishing. <br /><br />I am just learning how to troll with dipsys and dodger and flies for salmon. Caught 7 in 2 hours on only four rods! <br /><br />Not bad eh?<br /><br />Anyways, if it is a major problem with the boat, then I will throw a hissy fit to the marina I bought it from since they said they would fix the problem which they originally thought it was the accelerator pump

 

[horndog]

Re: Mercr 2.5L loss of power on acceleration

well..<br /><br />I called the mechanic and he said it is a fuel issue for sure. He stated to make sure the timing is set properly and see if there is any play in the accelerator pump arm, which there was. <br /><br />accelerator pump is working fine, and i tried straightening it out a bit which seems to help. <br /><br />Also I noticed play in the throttle linkage on the carb. Looks like there was washers missing, so I put a washer on and tightened it up which all seems to help. <br /><br />Granted its not perfect, and wonder if it ever will be. I definately think its carb related and need to find out if I should keep straightening the accelerator pump linkage arm till it goes away. <br /><br />what do you think?