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Tune up for 4.3 merc

J

JimA82

Regular Contributor
Looking for advice or tips on tuning up a Merc 4.3 LX V6. Went by a shop today, and sched to drop off on Wednesday, but been thinking how hard can it be to change plugs, gap and replace. Distributer/points and what not, timing?. Now I have not done it before on this one, except on my last boat which had a AQ130 I did quite a bit to that freaking thing from complete head rebuild to various other wonderful things. I am not totally without skills, but should I just let them do it and be done with it. Also no idea when the drive was ever off, been reading it should be done every few years.

Anyway any thoughts and or advise would be appreciated. It's a 92 Bayliner, and there are a few other cosmetic things that need to be addressed as well, but nothing serious.

Thanks! Jim
 
Mercruiser V6 1992 is electronic ignition. NO points.

Ignition Replacement parts

Cap
rotor
Pick up sensor inside of distributor. Note: if completely encased in black epoxy it has been replaced to current version. If it is not all black replace to current version
Wires. Most OEM wires measure ~ 5000ohms per foot. If you want to start fresh, but new ones. OEM will work just fine. OEM = Original Equipment Manufacturer
Spark plugs, Use correct ones and gap to spec

Ignition parts listing here
https://www.marineengine.com/parts/...-0f001219/distributor-and-ignition-components






Outdrive service is a lengthy explanation. Not feeling it this morning
Maybe someone else who feels like typing a small story will respond
 
kghost said:
Mercruiser V6 1992 is electronic ignition. NO points.

Ignition Replacement parts

Cap
rotor
Pick up sensor inside of distributor. Note: if completely encased in black epoxy it has been replaced to current version. If it is not all black replace to current version
Wires. Most OEM wires measure ~ 5000ohms per foot. If you want to start fresh, but new ones. OEM will work just fine. OEM = Original Equipment Manufacturer
Spark plugs, Use correct ones and gap to spec

Ignition parts listing here
https://www.marineengine.com/parts/...-0f001219/distributor-and-ignition-components






Outdrive service is a lengthy explanation. Not feeling it this morning
Maybe someone else who feels like typing a small story will respond
Click to expand...

Thank you! No worries on the outdrive. I watched a few YT video's on it, I feel I could do it, but that bearing removal and install looks like it could be a pain in the a--? I looked for some on tune up's and what not didn't really find anything but did not look that hard. We have a nice weekend up here in the PNW so going to open the engine up and look around better than I have.

Late Summer when I got the boat, I changed the fuel filter and the oil and cleaned up the carb/metal filter thing. Couple things the temp gauge doesn't work nor the fuel gauge. I can live with the fuel gauge, but I gotta have temp sensor.
 
The term ---" tune up "----Does not apply in many ways.----Electronic ignition / sparkplugs that last for years and years.-----Fixed jet carburetion or fuel injection.-----Spend your money on new filters.----Top quality gear oil.----New water pump impeller every 2 / 3 seasons.
 
racerone said:
The term ---" tune up "----Does not apply in many ways.----Electronic ignition / sparkplugs that last for years and years.-----Fixed jet carburetion or fuel injection.-----Spend your money on new filters.----Top quality gear oil.----New water pump impeller every 2 / 3 seasons.
Click to expand...

I disagree for this post.

This appears to be a new boat to him

I would and I did with my own boat, replace all ignition parts with new to start with a baseline of new parts.

Then one could say 8-10 years before any need to replace is needed.

As far as the outdrive service,

Videos on Youtube may not be whats needed................

You have ujoint bellow, water hose, shift cable bellows that needs careful inspection they last 8-10 years in fresh water 2-3 years in salt water, Gimbal bearing,

COMPLETE water pump impeller assembly replacement including pump base.

Pressure check drive to make sure all seals are good. Replace based on results.

Use Mecruiser High performance gear lube only !!

This is a standard base line pre use maintenance process and I may be missing a few things........

I do this to any boat that is used but new to someone.............
 
Yes, it is a new boat to me. I bought it from my business partner in August close to end of season here. He was the type that would have it winterized, use it once or twice a summer then winterize it, rinse repeat. I don't think he knew where the engine even was. LOL. He bought it from someone else 4+ years ago. He had it serviced a few times but he can't remember what was done to it. It must have had some saltwater exposure (not from him) as the outdrive is pitted in some places.

I changed the oil and filter, and the fuel filter as well. I also changed the gear oil with the recommended blue stuff. We used it guessing 3 or 4 times before fall was setting in. I winterized it and put a space heater in there and would plug in when I saw it would be getting really cold.


Things I assume need to be done.

T-stat not working, maybe bad sending sensor or the stat itself? Priority!

Gimbal bearing and the water pump/impeller and the gasket between drive and transom bellows also, not sure how to do a pressure test? High on list priority

Plugs and associated things that go with it? It is easy to do I believe so will do it.

Gas gauge not working, not high on my priority but will deal with it at some point.

Cosmetic stuff and what not.

There is a soft spot between the two front seats. Yes I have read the horror stories on these boats and rot. What is weird if I look forward from the front of the engine just above the gas tank there is about a 3 or 4" space all the way as far forward as I can see and side to side. There is no ski locker, it is like a deck above another deck. Top deck being carpet that I am going to get rid of. I hate carpet in a boat.

I will deal with the above soft spot, when the weather warms up a bit more. I am keeping my fingers crossed on the results I find.

Thanks again for the replies!

Jim
 
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1. T-stat not working, maybe bad sending sensor or the stat itself? Priority!

What or how do you know this? Does the gauge not show temp?

The best and easiest way to test temp issues is to have a stand alone test temp gauge rig with three wires attached. Go to any marine supply store and buy a brand new cheap temp gauge of any brand

Red for power +12+, Black for ground -12, and tan for sender. YOU MUST REMOVE wire form sender before attaching test rig otherwise it changes ohm reading gauge will see. One wire connected at a time.

This will tell you if the sender or the wires or the gauge is bad all at the same time.

Run engine until warm, What does dash gauge show? If nothing, Disconnect wire at sender at engine and connect test rig and see if there is temp. Most marine engines should be around 150-170* depending on what thermostat is installed (143* or 160*)


My test rig, see image

20180715_093705.jpg



2.Gas gauge not working, not high on my priority but will deal with it at some point.

Gas gauge is important! This is an easy diagnosis. two wires, Pink and Black. Pink is from sender, Black is ground.

Sender is a variable resistor. ~60-80 ohms to ~240 ohms. Use an ohm meter to perform testing (with NO power on)
Find Sender on gas tank, Should be two connections, Pink and Black wires.
Confirm they are attached with clean good connections.
Four failures ,
Bad/broken ground connection,
Bad/Broken connection of pink wire at sender or wire to gauge,
Bad sender,
Bad gauge

If bad sender,
You may have to remove sender to test properly. If you do, be very careful and do not disturb the way it is assembled in case you need to replace. Also note the orientation of the float so it goes back in the way it came out.

A universal replacement fuel sender may have to be assembled to look like the original one you remove. This could require changing float arm length and bending float arm to the same profile as original.
 
So quick update.

Distributor and rotor had to have been replaced at some point but look old. the pickup sensor is not encapsulated, plug wires do look original if that is even possible from 92 but I have seen worse things before so guessing so? I did not pull the plugs but I plan to replace all of it either way.

Temp sensor gauge has power going to it as the needle moves a bit when I turn the ignition on, gas gauge does nothing and no lights in either. Will check on that once I get to it.

Looking more at the deck, I think someone replaced it as well at some point. I am going to open that can of worms, just not sure how far I am going to take it yet. I danced that dance with the 1972 Trihull I redid 3 years ago not to mention the AQ130 I half rebuilt. I don't need to spend half my Summer tearing this thing apart. I would sell it before I do that again, will see what I find.


Question on the exhaust manifolds, exterior wise they look in good shape. I am assuming they have been worked on as the bolts look to have been removed somewhere along the line. The edges of the gaskets I can see are rusted, but there is no sign of water leakage from them on the outside nor at the block area. Do I dare take one off and see what I see, or just leave well enough alone. Again maybe another can of worms?
 
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racerone said:
I would not spend any beer tokens on this boat.----Most 1992 Bayliners have been scrapped.
Click to expand...

Bold statement considering you have not seen it! If I thought it was at that point, which it isn't. I wouldn't waste my time with it. Over all, it is in pretty good condition. The motor ran strong the few times I had it out late in the Summer, and yes the interior needs some TLC and the deck will be addressed amongst the other things mentioned above. But it is far from being sent to the junk yard.

But I appreciate the thought, thanks..
 
""Question on the exhaust manifolds, exterior wise they look in good shape. I am assuming they have been worked on as the bolts look to have been removed somewhere along the line. The edges of the gaskets I can see are rusted, but there is no sign of water leakage from them on the outside nor at the block area. Do I dare take one off and see what I see, or just leave well enough alone. Again maybe another can of worms? ""


The concern is if the boat was in salt water when used by prior owner (s).

If it was that may explain why they look as they do.

If the boat was used in fresh water only then exhaust manifolds and elbows can last 30-50 years with no issues.

My boat is a 1987 and still has original exhaust manifolds and elbows and have never been removed/serviced.

I would leave them alone as there does not appear to be any issue at this point.

Your concerns have to be water tested under load and boat run at 1/2 to 3/4 throttle for a while to see if there are any issues with internal leaks.

Running on a trailer in neutral does not always show these issues.


As far as your floor.

Remove interior, pull floor out, Cut New Marine grade plywood to fit. You can encapsulate it in a fiberglass resin with loose fibers mixed in.
Sand everything smooth and install.

The mounting "Joists" that the new floor screws into may be wet so they may need to be sister-ed with fresh pressure treated lumber for a good surface to screw into.

I would strongly recommend re-carpeting the floor. Use new marine carpet and good marine carpet adhesive.

Go with a neutral color such as grey.

People like carpet under their feet.......No sliding around!! Also less chance of a beer bottle breaking if dropped....


"""Distributor and rotor had to have been replaced at some point but look old. the pickup sensor is not encapsulated, plug wires do look original if that is even possible from 92 but I have seen worse things before so guessing so? I did not pull the plugs but I plan to replace all of it either way."""

You should do as I recommended and replace everything (ignition) with new parts to start with a known good baseline. You wont regret it!!

I did so in my boat when I purchased it. My boat had only 250 hrs of use when I bought from original owner. I still replaced everything (Cap, rotor, sensor, wires, plugs) to start with all new baseline and that lasted over 12-15 years before I redid everything again as a preventative measure.

I redid all of again two years ago, again as a preventative measure....Cap, rotor, sensor (Encapsulated, three wire where the third wire is a ground) and high quality plug wires.
Use OEM or Sierra as shown below. The Sierra are a good wire!

I went with Sierra 18-8821-1 - Wire Set for my V8

Sierra 18-8810-1 for your V6
 
Thank you, I plan on doing that. As for the deck, when I re-glassed the 72 truhull I had a couple of years ago, I checked the stringers for rot. They were all wrapped in fiberglass, I drilled some pilot holes in various places and found no rot to my surprise. Guessing there had to be some but I could not find any and it was solid all when I was done. Either way it would have outlasted the AQ130 that was in there. I ended up using out door type carpet sections that I could remove and let dry when wet plus wash the deck off with a hose when it needed it. Actually worked pretty good, vs gluing carpet down. So will see once I get to that point. I need to order the engine parts, so I am going to start pulling up the old carpet and inspecting what it underneath. That soft spot has to come up and I am replacing the dbl seats with singles so they are coming out as well.

Thanks again to all for the advice I appreciate it.
 
So I am waiting on parts to come in, but on the port side of the block if your looking forward. There is a sensor screwed into the block that has a plug in it, the temp sensor is on the front of the engine ao I am assuming this is a oil pressure sensor?


I also had my suspicions that someone covered the original deck with another and I was right. I pulled up the carpet and there it was. I undid all the screws and removed the pcs to see how it looked and it was not as bas as I suspected. At least they pulled up the original crappy deck that was put there by Bayliner. Stringers looked good from what I can tell, there was a bit of rot where the soft spot was but that was it. Gas tank was in ok shape, I ,ay replace but they are pretty freaking expensive. I will also be able to use the original pieces for a template to cut the new ones I will put in there. No they did not glass it in or use marine grade ply either. So I will be replacing it with that and glass in.

I have read lot's of horror stories on Bayliner going cheap when they built these boats, they were not kidding!
 
What color is the wire (s) at the sensor? Port side? Where? Next to oil filter? Purple with yellow stripe?

Passenger (port) side of boat has the oil filter.

The electric fuel pump wiring goes there.

There should be a Tee connection so to speak and a "sensor" which is actually a oil pressure switch.



Power comes from key switch two places, Crank and on/run

When you crank the engine, the power is supplied from the starter solenoid to the fuel pump by passing the OIL PRESSURE SWITCH to allow gas flow to start engine.

Once started and the key is returned to the on/run position, the ignition on/run power (+12 Volts) now goes to fuel pump but goes thru the OIL Pressure Switch. If oil pressure drops below ~5psi the switch opens and stops power to fuel pump.
 
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I went out and pulled the plug out of the sensor and low and behold it was barely plugged in, but somebody had jumped it with a wire. it has one solid purple wire and another purple with the yellow stripe going to the plug. And it is up and just back of the oil filter area. Guessing something like the sensor has failed, hence the jumping to keep the fuel pump working??
 
JimA82 said:
I went out and pulled the plug out of the sensor and low and behold it was barely plugged in, but somebody had jumped it with a wire. it has one solid purple wire and another purple with the yellow stripe going to the plug. And it is up and just back of the oil filter area. Guessing something like the sensor has failed, hence the jumping to keep the fuel pump working??
Click to expand...

Ayuh,..... It's not a sensor, but it's an oil pressure switch, that turns on at 'bout 5 psi,....
 
bondo said:
Ayuh,..... It's not a sensor, but it's an oil pressure switch, that turns on at 'bout 5 psi,....
Click to expand...

Well call it what you want, and I get that. That said it senses oil pressure and trips the switch at 5lb and it was jumped. Thank you for clarifying it. Either way I am guessing while I am buying parts I might as well change it, of course I am assuming it's bad as it was jumped by someone?
 
Sorry Bondo, I was in the middle of a crisis with one of my workers and a homeowner. Did not mean to come off so snarky.
 
YES it is better to start with known good so purchase a new one

Jumping the pressure switch is commonly used as a short cut only,
Say after a long winter storage and all gas has evaporated in the carb, You jump the connector, turn key on/run and pump will run and fill carb up. Try to start and if it starts quickly you shut off engine and remove jumper and reconnect the connector to pressure switch. This avoids lots of cranking after cold storage or when boat is brand new and there is little to no fuel in system.

The oil pressure switch MUST be functional per coast guard regulations!! This is true for all electric Marine fuel pump systems.
 
I know it's not the right forum, looks like most replying here also do in the gas section. But any thoughts/recommendations on a under deck fuel tank? Seen a few the dominant one seems to be Moeller but reading mix reviews on quality. Looking for 18/20 gallon rectangle type to fit under deck. Current one looks not bad, but since I am redoing the deck may as well replace it. Thanks!
 
So a 20 gallon tank for a 4.3 is what about 45 minutes run time? Ha ha ha just kidding. If you are fitting an under deck tank, I'd want an aluminum one that's been certified. I have never been a fan of roto molded tanks. I guess they're OK but I just like aluminum ones better. I guess I feel like I can strap it down tighter or something.
 
Thanks! Yeah, I don't know, I only had the boat out a few times late last year and just topped the tank off each time 5 to ten gallons if that. Just keep looking at it and thinking I should replace it. I have not measured it yet; it is roto mold guessing 4 to 5' X 2.5 x 8" maybe, with 3 holes that run through it top to btm. The top has kind of collapsed/bowed in like someone has been standing on it if you will, and pretty sure it is original. An aluminum tank is not really in the budget, it could be if needed but compared to the roto mold they are spendy.
 
JimA82 said:
Thanks! Yeah, I don't know, I only had the boat out a few times late last year and just topped the tank off each time 5 to ten gallons if that. Just keep looking at it and thinking I should replace it. I have not measured it yet; it is roto mold guessing 4 to 5' X 2.5 x 8" maybe, with 3 holes that run through it top to btm. The top has kind of collapsed/bowed in like someone has been standing on it if you will, and pretty sure it is original. An aluminum tank is not really in the budget, it could be if needed but compared to the roto mold they are spendy.
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tank was likely originally covered with a carpeted piece of plywood that is screwed down so you can access the fuel tank. These usually rot fairly quickly likely bowed and now your tank top is bowed in. Nothing wrong with a plastic tank for most users, I’ve never had an issue with one
 
Dieter said:
tank was likely originally covered with a carpeted piece of plywood that is screwed down so you can access the fuel tank. These usually rot fairly quickly likely bowed and now your tank top is bowed in. Nothing wrong with a plastic tank for most users, I’ve never had an issue with one
Click to expand...

Thank you, I was looking at it again this afternoon and you may be right. The deck I pulled off was not touching it, but that doesn't mean the deck before it didn't. I mean it is not terrible, I pulled the float out and it looks fine and the gauge works. There is some bits of debris I could see in there, so I may just drain it and clean the tank out best I can. It is 60" x 2.5 X 11 to like 5 and tapered or beveled or angled at the btm. Honestly it might be better built then new tanks today. Heck it might even be American made, no idea.. I just need to figure out where to support the new deck above it. I wanted to glass everything in, but I could save a section so it is removable. This boat is covered under a carport, with a cloth cover over it, it will mostly be used at the lake and not subject to any real rain or water coming in. Probably will go crabbing, this Summer, that said I tend to take care of things. These boat owners that pay crud loads of money and leave their boat to sit in the weather 24/7 or just plain don't take care of them drives me crazy. I don't care what you pay for a boat, you leave to the elements in the PNW and it's gonna rot. Sad deal all around. LOL
 
JimA82 said:
Thank you, I was looking at it again this afternoon and you may be right. The deck I pulled off was not touching it, but that doesn't mean the deck before it didn't. I mean it is not terrible, I pulled the float out and it looks fine and the gauge works. There is some bits of debris I could see in there, so I may just drain it and clean the tank out best I can. It is 60" x 2.5 X 11 to like 5 and tapered or beveled or angled at the btm. Honestly it might be better built then new tanks today. Heck it might even be American made, no idea.. I just need to figure out where to support the new deck above it. I wanted to glass everything in, but I could save a section so it is removable. This boat is covered under a carport, with a cloth cover over it, it will mostly be used at the lake and not subject to any real rain or water coming in. Probably will go crabbing, this Summer, that said I tend to take care of things. These boat owners that pay crud loads of money and leave their boat to sit in the weather 24/7 or just plain don't take care of them drives me crazy. I don't care what you pay for a boat, you leave to the elements in the PNW and it's gonna rot. Sad deal all around. LOL
Click to expand...

Would definitely allow for future tank removal. Haven't seen a typical 19-20 ft BR where the panel above the fuel tank wasn't removable, makes no sense to glass it in. My current boat (2004) has a glasses floor with a glassed/gel coated panel that screws above tank so it can be pulled.

It was mentioned and dismissed (#11) above- but considering somebody did a quickie deck over did you fully check the stringers and transom for rot before your really get into thi$? Not that it cant be fixed just know what you are getting into...
 
Dieter said:
Would definitely allow for future tank removal. Haven't seen a typical 19-20 ft BR where the panel above the fuel tank wasn't removable, makes no sense to glass it in. My current boat (2004) has a glasses floor with a glassed/gel coated panel that screws above tank so it can be pulled.

It was mentioned and dismissed (#11) above- but considering somebody did a quickie deck over did you fully check the stringers and transom for rot before your really get into thi$? Not that it cant be fixed just know what you are getting into...
Click to expand...

The transom is solid, and I also removed a couple of motor mount lags and they are in solid wood. I pulled all the decking up, and two of the stringers where the soft spot was between the two front seats had rot. I cut it out to solid wood then sandwiched it with two pcs treated 2x4. Glued and screwed. Like I said above overall it was not bad, could have been a lot worse for sure.

Could there be more rot down in places I can't see, it is a possibility I suppose. But I banged around where I could and they sound pretty solid all around. That said at this point I am not going to tear into this thing to find it or not. If I get another 10 years out of it, pending the motor lasting I will be happy. I will also be 69 if I am even still around. These days who knows. LOL
 
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In a properly constructed hull the wood inside the stringers is just a cheap form for laying the fiberglass roving on. The glass/resin should be built up thick enough to provide ample structure without any help from the interior core.
 
o2batsea said:
In a properly constructed hull the wood inside the stringers is just a cheap form for laying the fiberglass roving on. The glass/resin should be built up thick enough to provide ample structure without any help from the interior core.
Click to expand...

In a Bayliner I am not sure anything is properly constructed from what can tell and have read.
 
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