PLEASE HELP!!1988 volvo 5.7 aq271c stalling losing rpm

[KTOWNCABBY]

Hi Folks; Was Out Last Night Ran About 20 Miles Revving Around 3500-3800, Boat Worked Fine. Stopped For Dinner About 2 Hours And On Way Back After Bout Half An Hour Of Running Around 3700 Rpm Boat Started To Lag. Dropped The Rpm's Down To 3500 It Seemed To Run Ok But Then Dropped Rpms And Stalled. After That The Boat Would Only Keep Running At Around 2000 Rpm. The Thing Stalled About 3 Times But Would Start Right Back Up. Temperature Was About 130 Degrees. Oil Pressure Seemed High To Me Right Before This All Happened; Just Under 80 Psi. After First Stall It Was 60 Psi Were It Usually Is While Operating. The Oil Level Was Fine When I Checked It. This Boat Sat For 18 Months And I Purchased It A Month Ago. Have Put 3/4 Of A Tank Of Gas Through It Since Purchase. 1/4 Tank Of Fuel When This Started Happening. I CHANGED THE FUEL FILTER AS THE MECHANIC AT MY MARINA SAYS THERE COULD BE WATER IN THE TANK FROM IT SITTING FOR 18 MONTHS. WOULD THIS CAUSE THE SYMPTOMS I'M DESCRIBING. WOULD ANYTHING ELSE OTHER THAN BAD GAS CAUSE THIS PROBLEM? ALSO WONDERING HOW HIGH THIS ENGINE WILL REV AND WHAT IS A SAFE RPM RANGE TO OPERATE IT AT. I HAVE BEEB CAUTIOUS NOT REVVING IT AT OVER 3800 RPM JUST TO GET IT ON PLANE. Any Opinions Appreciated
Ktown Cabby

 

[Maclin]

Re: PLEASE HELP!!1988 volvo 5.7 aq271c stalling losing rpm

I am not sure if you put the new water separating fuel filter on before or after these symptoms, but if it was before then change this one out again, and buy a couple as you may need to repeat this. Try to keep the old filter full as you take it out so you can pour the contents into a glass container to see what it looks lik, see if there is any water in it or discoloration of the fuel or chunks of stuff. If the gas looks bad or has water and this cycle repeats more than a couple of times it is probably time to drain the tank and start over.

The carb may need a rebuild, if it sat around for a few years with old gas in it that could cause some corrosion that could have broken loose and clogged some passages. If there was water in the filter then the carb bowls need to be drained

Usually bad gas or gas with water will cause the engine to sputter and backfire and not want to run at all.

Weak fuel pump can cause that problem, but usually it surges as it runs dry then gets fuel back up to the carb, not just run steady at a lower rpm.

 

[KTOWNCABBY]

Re: PLEASE HELP!!1988 volvo 5.7 aq271c stalling losing rpm

What I'm Concerned About Is The Increase In Oil Pressure, It Was Operating At Around 60 Psi While Revving At 3500-4000 Rpm But Increased To Almost 80 Psi Right Before The Issue Started. The Next Morning After I Changed The Filter I Started It And Same Oil Pressure Just Below 80 Psi. I Let The Motor Run For A Good 20 Minutes Until The Water Temp Was 130 And Revved It To 2500rpm A Few Times While In Neutal With No Hesitation Or Sputtering. There Is 1/4 Tank Of Gas Left In The Tank. Should I Burn This Off At The Dock? Would It Help To Use Some Stp Water Remover In The Tank To Help Dissipate The Water If There Is Any? The Old Filter Was Full When Removed But Looks Like Gas To Me.

 

[Maclin]

Re: PLEASE HELP!!1988 volvo 5.7 aq271c stalling losing rpm

I meant to give you the rpm range. Top rpm is 4400-4600.

I am not sure what would make the oil pressure reading change like that. My first inclination leans towards an electrical issue of some kind that changed the gauge's behavior.

Distributor cap and Rotor, "leaky" plug wires, spark plugs, improper gap on plugs or wrong plug heat range or wrong plug itself......any of those can limit rpm. I know when I bought my dist cap the Volvo oem one was way better than a cheapy they showed me. The Volvo one had the extra molded in rings around all of the terminals on the inside, that keeps chances for crossover spark down.

My boat had been sitting for more than 2 years, the Holley 4bbl carb had lots of sediment and crud build up inside and had to be rebuilt.

 

[steve_garofalo]

Re: PLEASE HELP!!1988 volvo 5.7 aq271c stalling losing rpm

I just bought an 82 Eliminator with a Volvo 270 drive, Chevy 350 Engine.

Had (have) the exact same problem you are talking about.

The boat sat for quite a while and ran great for the first 25 or 30 minutes or so,, then the exact same thing happened to me.. Changed plugs, wires, searched on here and everything led to bad gas/ carb blockage..

Took another carb off of one of my cars and the boat ran great! Picked up almost 10MPH and 500RPM's.. So I bought a new edlebrock marine version of the same carb..

Tossed that on and ran great for about the same amount of time, my guess is something dislodged in the fuel lines and now with the new carb I can't even get it to idle.. Put the other carb back on there and took the kids out for a day of tubing,, ran great all day till we "found" a submerged rock and greneded the prop..

I added the water remover, octane booster, all that other crap too.. My advice (and I am no where near as qualified as the rest of the guys) drain the gas if you can,, rebuild the carb, and start fresh.. The new gas that is out there is horrible with water absorbtion and "tarnishes" up quicker than most people think..