Merc 150 bogging down random times..???

[Keaten]

My merc 150 sometimes boggs down to about half power even though I didn't let up on throttle.. it slowly slows down by its self it runs around 3000max at that point.. it's at random times some trips it might let me run 5750 with no trouble but for only 2-3mins.then most aways it will act up.. my block halfs were leaking and I've fixed all that and it runs a lot faster and idles lil better...any help on the bogging down to half power randomly would be very helpful thank you.....

[donmac]

stator, switchbox,fuel line,pump,tank syphon valve.

[XstreamVking]

Fuel starvation most likely culprit......

[Keaten]

I've rebuilt fuel pump twice changed all fuel hoses new tank withdraw tube checked for air Leake serval times.. maybe I can run clear hoses one one trip to get a look at what's Goin on.. but I know the gas will eat that hose up if I leave it very long.. I've got a new stator and two new switchboxes I can put them on and try them also..

[Dave Strong]

You try hitting the primer when it starts to bog?

Dave

[Keaten]

I will next time to see if fuel pump is not working properly...thanks hard to remember all that stuff when it's happing...

[Dave Strong]

Also see if the primer ball is sucking flat when it happens.

Dave

[Keaten]

I don'tknow if it's normal but my electonics and volt gauge shows around 14 at idle and 17volts at wot hope that's normal seams high...

[Dave Strong]

Check it with a known good volt meter, 17 is high. Seen lots of guages that don't read accurate.

Dave

[Keaten]

It's 17volts on my lowrance hds and volt meter gauge it's got a 16amp stator...

[Keaten]

My primer bulb is suckin almost flat, when it started to bog I quickly stoped and killed the motor and the primer was almost flat... when I was pumping it back up it was slow to expand it self up again... got it pumped up could hear the gas filling up the carbs again.. fired right up again... I've changed the pickup tube in tank the little screen is still in the bottom of the tube. I've added a water separater filter in line and changed all of the fuel hose. Made shure the tank vent is clean and not clogged...when tank is really full gas will spill out of the vent on to the trailer.. but ive had trouble at all tank levels...Triple checked all hose clamps for air leaks, the primer bulb is new and is blue (not sure what brand) the fuel pump on engine is rebuilt and is doing its job well I guess...

[Dave Strong]

Did remove or knock the check ball from the anti siphon valve?

Dave

[Keaten]

Yes it's all straight though normal 3/8 barb fitting

[Dave Strong]

Try running a new primer ball have found the only good ones are OMC, Merc or Sierra. make sure the outlet of the ball is pointed up, higher than the inlet.

Dave

[mn808gade]

have nothing but probs with Sierra.with fuel the way it is I use ONLY OMC/Evinrude-merc's with the new liner inside donot move much fuel-th

[Keaten]

Ok I'll try a omc 3/8 primer bulb there's a dealer near me... thanks guys for your help...

[FMP]

Try running a new primer ball have found the only good ones are OMC, Merc or Sierra. make sure the outlet of the ball is pointed up, higher than the inlet.

Dave

I replaced the 2 stage original pump diaphrams on my dual fuel pump CHRYSLER with sierra diaphrams. Nothing wrong with the org. just 100 hours and thought it might be good idea. I got 5 hours running on the sierras' and both the small sides both pumps ripped right around, made getting back to the dock fun. Repalced them again with Merc parts and 40 hrs later still OK. Today you have to look at everything you buy and still might end up with crap.
Stick with MERC or OMC.

[Keaten]

Ok well the kit that's in the pump now is serria.gaskets only though i didnt re place the spring or the botton ontop of the spring.... maybe 2.5 hours on the new gaskets I ll keep that in mind thank you..

[FMP]

My primer bulb is suckin almost flat, when it started to bog I quickly stoped and killed the motor and the primer was almost flat... when I was pumping it back up it was slow to expand it self up again... got it pumped up could hear the gas filling up the carbs again.. fired right up again... I've changed the pickup tube in tank the little screen is still in the bottom of the tube. I've added a water separater filter in line and changed all of the fuel hose. Made shure the tank vent is clean and not clogged...when tank is really full gas will spill out of the vent on to the trailer.. but ive had trouble at all tank levels...Triple checked all hose clamps for air leaks, the primer bulb is new and is blue (not sure what brand) the fuel pump on engine is rebuilt and is doing its job well I guess...

Check ball , pickup tube, primer bulb, your pump is doing the job or the bulb wouldn't collapse. I'm guessing you didn't put the filter between bulb and tank.

[Keaten]

Tank , water sep.filter, primer bulb, fuelpump, carbs,, Is the order I've got it plumed...

[Dave Strong]

Had an Allison with a 225PM a couple years ago drove me nuts. Would run fine on our remote tank primer ball seemed ok. Replaced the primer ball with a Sierra ball, problem fixed, that was 2yrs ago.

Dave

[Robby321]

Did ya make SURE the tank vent is not obstructed? That will damn sure make a bulb go flat. If OK, yep, get a new bulb.

[FMP]

Any chance that the water sep. filter is holding things up enough to collapse the bulb and cause a stop . Try without the filter, or bulb or switch order.

[Keaten]

Tank vent is clean with the bulb flat I've taken gas cap off it didn't change..or rea lace air.. I'm think bad bulb ,
crazy it's a easy fix... hope thanks all it is..

[Keaten]

Tank vent is clean with the bulb flat I've taken gas cap off it didn't change..or rea lace air.. I'm think bad bulb ,
crazy it's a easy fix... hope thanks all it is.. I've try ed different in line filter by its self same issue

[FMP]

No way the bulb is in wrong direction??? You only do that once, been there.:nonod:

[Keaten]

Na the arrow pointing to engine... I've double checked that...

[FMP]

I've try ed different in line filter by its self same issue[/QUOTE]

If you tried it by itself , then it's not the filter or the bulb! What size pickup i.d., I've seen pickup tubes collapse, but not new ones.

[FMP]

Canoes are nice.

[Keaten]

The primer was never removed for the test with different filted...

[Robby321]

Gotta be a bad check valves the bulb. Been there, done that. Try new and see. When I built/rigged the Flatbottom (avatar) and bulb laying horizontal would NOT "flood" the Merc carbs even felt hard. Had to point it up to get a result.

Also how "new are the hoses? This new crap EPA gas hoses have a "membrane" inner (chit plastic liner) that will bunch up on install and block flow. But don't think thats yer prob as like said.."random". Do a new bulb and best to have it close to the motor, and "arrow" pointed up in vertical. But bet your bulb has like said bad flap valves..."piece of junk", as they don't make them like they use too. Wish the best as chit like that sucks, when ya deal with the "WTF" is wrong?

And the reason I chimed in here was title "150 Merc bogging down" Thing is I had a 74 Switzer XS1500 that went from WOT to "need more gas" bogging down. Lay off and back WOT for a bit and again. After a lot "detective work" and no result called my Merc Guru who built the motor. Told me he just got a service notice Merc to remove the 3 carbs gas in hoses, and REMOVE the small screens to the float bowls. YEP! One was clogged, and ran like the beast it was after that!

[Keaten]

I'll change my bulb and make it vertical. ... all fuel hose is 3 months old ,3/8 size.... the fuel pump on engine has a new screen in it as well...

[Dave Strong]

If the ball is going flat generally its a restriction prior to the ball. That fuel line with the plastic liner is junk. Stiĺl could be a bad ball.
Is the tank aluminum or plastic? If its plastic could be deforming and blocking the pickup.

Dave

[Dave Strong]

There are cheap brass fittings that might be 3/8" Od but have 1/4" Id.

Dave

[Keaten]

Plastic tank,,,,whats a good fuel hose.... to use

[FMP]

ditch the filter and run Shell 91 no alc or better.

[Dave Strong]

Plastic tank,,,,whats a good fuel hose.... to use

We use Sierra hose, grey rubber no liner can't remember the number off hand. But we don't have to deal with ethanol.
Any way to raise the pickup in the tank 1/4"?

Dave

[Keaten]

Ok I can cut the pickup tube and make it a lil shorter... I can say when I installed it last time I cut the end at 45deg angle.... if I take it out again I'm Goin remove the lil screen in the bottom of tube too....

[Dave Strong]

Ok I can cut the pickup tube and make it a lil shorter... I can say when I installed it last time I cut the end at 45deg angle.... if I take it out again I'm Goin remove the lil screen in the bottom of tube too....

Don't need the screen you have a water separating filter. Now to start at square one if you brought your boat to me at work. Would go to the lake with a known good 5gal remote tank and fuel line with primer ball. First step would be to get your boat to act up. Then hook the shop remote tank and hose to your motor, if it works fine then hook the shop fuel line to your tank. If it acts up we know the problem is between where the shop fuel hose hooks to your tank and where the fuel pickup is.
Get where i'm coming from? Process of elimination starting at the fuel pickup. ;) Customers hate it when we waste money replacing parts and don't fix the issue. Just stand back give your head a shake take your time and eliminate things one thing at a time, don't get frustrated and start throwing parts at it willy nilly.
good luck and keep us posted.:D

Dave :)

[Keaten]

Thanks so much,... I'll get some stuff ready to test ....

[Robby321]

Would go to the lake with a known good 5gal remote tank and fuel line with primer ball.
good luck and keep us posted.:D
Dave :)

Thats the way to "isolate" as I done many times! Great reply Dave!

[Dave Strong]

Thats the way to "isolate" as I done many times! Great reply Dave!

Ya funny how people hate to pay $110.00/hr +parts to guess at chit. Don't matter how long a guy has been wrenching no crystal ball that you can say 100% seen this before just put this part in and she will be all good.
Wish it was that easy I would have been retired years ago.
Biggest thing is deal with the simple baisics first. ;)

Dave :)

[Keaten]

Ok did test run today. I disconnected my water sep. Filter from tank and concneted a smaller test tank.. with everything other side of water sep.filter the same including the primer ball.
Ran boat 7 miles at 5800rpm with zero issues. ...


..

[Keaten]

Its something to do with the tank in boat... i learned that..

[FMP]

Nope, it's MAGIC!

[Robby321]

OK, something wrong in the tank. What who knows. Can ya get a peek at it? Bow, middle hull? Like said before "whats it made of" Need info year/make boat, years old, etc.

On the "sep tank" a friend mine has a pristine restored Dorsett El Dorado, with a just built 80 Merc period correct. But it sat for 3 years in his heated shop, and had gas in the new installed Alum bow tank. Motor never pickled. As other boats and "life" in the way..(plus TOLD him as us salt water?..do fresh lakes!) He asks me to "what to do". So I drained with a elec pump all gas out the tank as the hose to motor. Sliced it in half and did a "fit" with a 3 gallon tank to fire the motor. Then a inline filter connect to use the front bow tank if wanted. Fired up fine after 3 years, pumped water fine. Did heavy oil and fogged gas running out the carbs. Its back his shop and TOLD him. "Good for two years sitting, but then I'm gonna have to yank the L/U for impeller, and we gotta fire it and "keep the crank seals .."Wet"
Wish the best!

[Keaten]

Plastic tank in bilge area..yellowish clear....I've cleaned it out..cut my new pickup tube 1/4 shorter removed screen in tube..next I'm Goin triple check tank vent for clogging.. engine ran perfect on test tank with the same hose,fliter,ball pluming all ready in boat... so know the boat tank is the problem. .

[Dave Strong]

Check the vent hose for soft spots, have seen some not fuel rated.

Dave

[Keaten]

Ok the vent hose is 5/8 size ,
it's dry and cracked looking on outside. .. I'll replace it anyways... it's only 18"long

[FMP]

What are those little mud wasps called , anyway maybe they set up shop in the vent tube,.... long shot or still MAGIC.

[Robby321]

What are those little mud wasps called , anyway maybe they set up shop in the vent tube,.... long shot or still MAGIC.

Mud Daubers. And yep, new vent tube as ya say the tanks been cleaned.

[Dave Strong]

Could eliminate the vent by running with the cap off.

Dave;)

[Keaten]

Well water will get in tank if any fast stops..ha if it dies... I'll plum a temp. Hose same size in its place... I've also haven't run it since I cut and removed the screen from tube... I cut 1/4 off

[Keaten]

Ok its fixed it was the pickup tube in take..i cut .25 of and removed the screen in tube.. is running wot.for ten miles with no bogging...thanks so muck guys.... all about finding the source..thanks dave..

[Dave Strong]

Glad to see your back running good.:thumbsup:;)
Simple things can make a guy crazy.:eek:

Dave :)

[FMP]

Ok its fixed it was the pickup tube in take..i cut .25 of and removed the screen in tube.. is running wot.for ten miles with no bogging...thanks so muck guys.... all about finding the source..thanks dave..
Don't burn a piston.

[Robby321]

Ya GOTTA think the "little things"! Tell ya a fast me and my HD Shovelhead.

Over winter season spring went to fire it up. Hit the "electric kick stater" and only a little pop. Kept on trying and getting zip. Then the starter solenoid went bad. Replaced that and next the "Bendix" gave up the ghost. Replaced and still no fire? Good spark off the plugs? THEN THE OLD BRAIN kicked in gear..

HA! Remembered I drained all the gas out fall! What a dumbass me!