Out of the hole hesitation, stumble, stall. 5.7L Merc TB-V

[JoJoBetsy]

Hello all,

Been running awesome and now here is what I get:

First the goods: Merc 5.7L TB-V s.n OL351262, Alpha Gen II

From the dock to the ski area about 15 minutes of moderate to full throttle. Get my skier out and go to full throttle and all I get is sputter, putt, putt, stall, idle. Okay, try again, sputter, sputter, off the throttle and solid idle. Wow, that's the first time I've had that happen, let's check under the hood. No particular alarming odors. No rough idle and out of gear revs up nicely. Put my hand on the starboard riser and it is hot as all get out, I mean you don't want to leave your hand on it. That's odd. Try the port side and it is warm, I can easily leave my hand on it. Humm? Clogged lines/riser, bad impeller or circulating pump? Nope, I pull the blue plugs under the manifolds and both have water flowing nicely.

Well that's it for the day, put it in gear and idle it back to the dock for some home inspection/maintenance. I'm thinking clogged riser or manifold, maybe a thermostat, but how would that make the hesitation occur during acceleration. Well, I take off the risers and they are pristine, replace gaskets and torque them back down. I did get a glimpse at some crappy looking flappers and replaced both of them. All put back together and now it is time for the thermostat.

Came out with ease, and after a check inside the hot water pan turned out to be working fine. I replaced the gasket and thermostat and ran on ears and humm, still have a hot starboard riser. Timing is next.

Here's where it gets wierd. I did everything the service manual asked for, grounded the purlpe/white wire to get into service timing mode and to my surprise I don't see a timeing plate/placard near the crankshaft. I looked all over for it and nothing. What I do have is a machined lined on the crankshaft and above the crank a machined "v" with whiteout on it. So I assume those are the timing marks and give it a shot. I get the machined crankshaft line to align up as best as I can by twisting the distributor but they never align perfectly. The engine is running nicely and it accelerates perfectly. So, I button it up and get it ready for a water test.

Out on the water today the same 15 minute trip at mid to WOT and put a skier in. Go to full throttle and sputter, sputter, hesitate, dead. Start it again, temp is 160 or so, idle is 650 and sure enough the starboard side riser is burning up, cannot even touch it for more than a couple seconds. Port side riser is warm and easy to leave your hand on. Boat goes in and out of gear with ease, all fluids are perfecto, and gas is fresh.

What gives? Carb...and if so, where to?

Thanks a bunch for reading and any help you can provide.

jb

 

[Don S]

Re: Out of the hole hesitation, stumble, stall. 5.7L Merc TB-V

Sounds like you are trying to blame everything on timing.
When was the last full tuneup? Cap, rotor, spark plugs.
How about the fuel filter? Any water?
What about the raw water impeller? How old is it? If it's over 3 years old, it alone could be your cooling problem.
Now, lets go to timing.
The timing mark on the vibration dampner is 0°, that single notch in the timing chain cover is also 0° Line them up on compression stroke for #1, and you have #1 TDC.
To set the timing, you either need to have an advance type timing light, get the sticker for the dampner that has the degrees marked on it, or do the math to mark your own degrees.
When you grounded that purple/white lead to put the distributor into base timing, did you do it while the engine was OFF?
Are you using a Mercruiser service manual?

 

[Bondo]

Re: Out of the hole hesitation, stumble, stall. 5.7L Merc TB-V

Your Problem sounds like a Fuel Delivery Issue........

Have you checked,+ changed the Fuel Filter,..??...

 

[JoJoBetsy]

Re: Out of the hole hesitation, stumble, stall. 5.7L Merc TB-V

I must admit, I am trying to say it is the timing, and most probably, the way I timed it doesn’t sound like what you have mentioned here, but I do everything the service manual said to do save for any carb adjustments.

Engine oil/filter, fuel/water separator, outdrive oil and impeller, distributor cap, rotor wheel, spark plugs all replaced two months ago, approximately 10-15 operating hours ago: running fine until now. Cleaned the spark arrestor and checked for raw fuel with the accelerator pump actuation and there are two nice jets of fuel.

The last time I posted [and I’m bummed I lost my rank with the changeover in forums styles] was when I posted pics about my possible riser gasket leaks. I replaced the starboard riser gasket and found out my leak was actually from the screw holes in the manifolds [a fellow poster said not to worry about those holes as they are for other systems]. Never had any other leakage and the engine ran fine with the starboard only riser gasket repair.

Now, the starboard riser is hot and the port warm. My Merc mech says this may be a normal condition but that it could also be related to a clog, timing, or thermostat. So I decided to replace both riser gaskets and look for a possible clog in the starboard riser. No clogs were found by visual inspection alone and both gaskets were pristine. The manifolds and risers are in good condition, light rust on the water side and normal exhaust carbon on the hot side [inside]. I noticed both flappers were trash so I replaced them and put everything together.

Next was timing. I have the Mercury service manual and followed the TB-V timing procedure. I grounded the purple/white wire to an engine mount and had an automotive timing light that also would read the RPMs. I look for the timing plate, and well, Don answered this for me. The timing light was connected to #1 plug and the machined line on the crank was jumping all over the place. I turned the distributor to get the line as close to the mark on the vibe damper as I could and figured I better take pics and get back on the forum before I do much else. RPM was 640-670 and holding; I tightened everything down and put her on ears.

Out of gear and throttled she ran perfect. Good acceleration and right back to idle. It shifted in and out of gear without a problem and I figured I had it worked out. On ears for about 10 minutes and that damn starboard riser is hot again. A quick look at the engine temp gauge shows 160°. So, I decide to take her for a water test.

Same story as before. 15 minutes out, skier in the water, go to full throttle and stumble, stumble, off the throttle. Skier lets the rope go and I go to full throttle turning hard port basically trying to replicate my symptoms and sure enough stumble, stumble…dead in the water. Fires right back up and idles like a champ right at 650. Try with skier again…I know a glutton, yada, yada, and same thing, CRAP!! Raise the hatch and yep, starboard riser is hot as hell. No alarming smells, fuel, overheating, etc. Everybody out of the water and idled her back to the dock for a craptastic day on the water!

At home I remove the thermostat for a stovetop test. Opens up right at 160° without fail. Reinstalled.

Next, I opened up my laptop and got on the forums. It’s like this. I have to fix this myself or my boat is G-O-N-E for a solid month. I did a forum search on hesitation problems and saw a post about how the Merc carb is prone to a lean-out condition and the symptoms are similar…except for that starboard riser heating up. I have never checked compression and other than looking at the accelerator pump operation have not touched the carb. It sounds like my timing attempt was bad and I am not exactly sure what an advance type timing light is. Aptitude is high though and if you guys are willing to help I’m sure I can make it happen.

A million appreciative thanks for any help provided.

 

[layne4]

Re: Out of the hole hesitation, stumble, stall. 5.7L Merc TB-V

Had a similar problem on my 5.7L about a month ago, when the boat was lightly loaded it came out of the hole fine, when the boat was loaded, out of the hole it was like someone turned the gas off. Took the carb apart, installed a new float kit and carb rebuild kit. Runs like a champ now, i would pay more attention to the carb. Your heat isssue on could be a lean or rich condition. Is it a Quadrajet carb?

 

[JoJoBetsy]

Re: Out of the hole hesitation, stumble, stall. 5.7L Merc TB-V

Nope, 2bbl Mercarb (is that a Quadrajet...I don't know). I'll wait for others to weigh in too but I am leaning towards a carb rebuild and re-timing as well. Thanks for the info. jb

 

[JoJoBetsy]

Re: Out of the hole hesitation, stumble, stall. 5.7L Merc TB-V

Fixed. In order of replacement/testing.

Replaced the fuel inlet filter - dirty.

Timed with proper advance timing light - needed it becuase as Don S pointed out I didn't do it right the first time.

Replaced the plug wires - original.

Replaced the coil - original and corroded and did not pass the ohm test.

Replaced the ingnition sensing unit in the distributor - original, really dirty, and had poor continuity.

Fixed all holeshot stumbling after the last two which were done at the same time. Thanks for the advice from all and if you have questions let me know.

jb