Newbe to MerCruiser 4.3 MPI or inboards as a whole

Hi Guys, firstly I would like to introduce myself, I am DJ from South Africa and recently bought my first inboard boat with a MerCruiser 4.3 MPI inboard motor. I have only ever had 2-stroke outboards, raced them, serviced them, built them. I use to be a valuable long time member of the iBoats forum up until they decided to block South Africa from their forum servers. This was quite a few years ago and using an anonymous proxy to try and help others become too much of a mission and I withdrew myself completely. I was well known in the Yamaha / Suzuki / Tohatsu / Mercury / Mariner / Inflatable Boats / Wakeboarding threads.
Anyway I don't want to bore anyone with my history story and I hope this is the correct place for me to ask my question about the MerCruiser inboard.

I hope someone can maybe help me or direct me in the right direction. I have no idea how to operate this engine, are there any procedures I have to go through before starting it up, things I need to do before putting it away etc etc. the guy I bought it from haven't used the boat in a few years and could not give me any details. Keeping in mind I am use to 2-stroke motors, are there a tell tale to show it is cooling? How do you get use to not being able to see the trim on the leg etc. I apologise if this sounds stupid but I would love it if someone can give me a quick run down and some tips on how to operate and look after this machine.

First of all, buy a Mercruiser manual! Then study it cover to cover.

On the tell tale, for some dumb reason most Mercruisers don't have one--mine included. I intend to add one, tapping off an elbow. For now, if the temp gage doesn't start climbing I know the pump is working--hardly an acceptable method.

Jeff

Is the boat on a trailer or does it sit in the water all the time? Raw water cooled or closed cooling?
Before you start the engine, do a quick visual. Look around for obviously loose parts, drips, leaks, anything that looks wrong. Run the bilge blower for at least 5 minutes. If there are any stray gasoline fumes in the engine area you want to be sure that you vent the compartment before putting any electricity to it. Change the belts and oil at least once per year. Keep your filters clear and keep spares on board. If you know your way around internal combustion engines, you'll be fine.
There are two gauges that address your concerns. The first is a temperature gauge that lets you know how warm the engine is. If it spikes high, you can be pretty sure the engine is no longer getting cooled properly. Another quick way is to put your hand on top of the exhaust riser. It shouldn't be so hot that you can't touch it. If you know where and how to change the water impeller, just do it once a year and keep an extra on board. If you suck up sand you'll want to swap in a fresh impeller (this can happen if you ground the drive and use reverse to pull the boat off the bar). Second thing is a trim gauge. This informs you of the uppy or downy-ness of the outdrive. Not super accurate but it gives you a pretty good notion of which way the drive is pointed. Your boat should certainly be equipped with the temp gauge. Not all have a trim gauge tho, so you may have to add that yourself. Buy only Faria gauges.
Do you all have a winter season in ZA?

Thank you for the replies guys, I do have a owners manual that I studied but some of the lingo makes no sense to me as it is not "my exact engine specific" so I don't know how to tell what drive I have on there, the model etc etc .... I will post a pic of my drive and my motor .... at the moment it is winter here and the boat is in storage so it is difficult for me to go to the facility everytime I want to check something out. That is why I thought I will do my homework before taking her out for the first time come spring. What I can tell you is that it is not closed cooling, it is definitely raw water cooled .... and with regards to that does it suck in water from the leg the same as a outboard does? There is no intakes in the hull itself or something to that effect? The engine was serviced by Mercury Marine in May so it is completely maintained. This boat lives in a garage and have never seen salt water, only ever got used in fresh water over weekends etc with 120 hours on the clock. Other than that it has no gauges other that the trim & tilt and the fuel tank, it has 2 digital gauges as per the pics ... one looks like a fish finder and the other I would assume will show the engine temp, speed etc? The batteries are dead so I have never actually switched anything on ... the owner wanted to charge the batteries and didn't realise that you never put a battery on a cement floor .... some people never learn ... anyway, I do have a few questions .... the manual keep on talking about opening a seacock before starting, what is that? And also to close the drain system .... which got me wondering, is there a drainage system for the engine itself? Does all the water not automatically drain out the leg like an outboard? Does this only need to be done after a weekends' fun? (Fresh Water Lake) Sorry for all the questions ....

I tried to add pics but it does not work, all jpg small size under 90kb each ...

Finally it worked ....

Yes you need an oil pressure and engine temperature gauge on the dash.

...you never put a battery on a cement floor

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Hmm I better apologize to all my batteries then. They've been living on the floor of the barn for the past 6 years....

re: : .... and with regards to that does it suck in water from the leg the same as a outboard does? There is no intakes in the hull itself or something to that effect?

Water inlet on MERCs ( and most stern drives) are "gills" on the leading edge of the lower unit.


The engine was serviced by Mercury Marine in May so it is completely maintained. This boat lives in a garage and have never seen salt water, only ever got used in fresh water over weekends etc with 120 hours on the clock. Other than that it has no gauges other that the trim & tilt and the fuel tank, it has 2 digital gauges as per the pics ... one looks like a fish finder and the other I would assume will show the engine temp, speed etc? The batteries are dead so I have never actually switched anything on ... the owner wanted to charge the batteries and didn't realise that you never put a battery on a cement floor .... some people never learn ...

Actually, putting batteries on a concrete floor only an issue if the outside of the battery is "dirty" with spilled battery acid, and the concrete floor is damp.

anyway, I do have a few questions .... the manual keep on talking about opening a seacock before starting, what is that?
If equipped, this valve is between the inlet to the raw water pump ( from your photo it looks as if this pump is the bottom pulley on your engine...check for hoses in/out) and the transom on the raw water inlet line.

And also to close the drain system .... which got me wondering, is there a drainage system for the engine itself?

Some MERCs have a "single point drain" which here in colder climates of the USA leads to many damaged engine blocks and manifolds.

Does all the water not automatically drain out the leg like an outboard?

While the leg MIGHT drain, the issue in some climates is the need to drain the engine block and manifolds.


Does this only need to be done after a weekends' fun? (Fresh Water Lake)

No....if above freezing.

Sorry for all the questions ....

Without questions, this would be a boring website filled with chest thumping and back self patting posts..."


Further.... There is a decal on top of the flame arrestor ( where the air cleaner would be on a car) that should have tune up info as well as a recommended Wide Open Throttle (WOT) maximum rpm (MAX RPM) range. With your "normal" boat load and a full tank of gas on a calm day, with a tuned up engine and fresh fuel, your engine should be able to rev up to within that specified WOT MAX RPM range. If it does not, you had prop issues. Many times owners want more speed and change props to the determent of the boat.

Assuming you can do this correctly, record the actual RPM achieved. When running the boat at cruise ( i.e. continuously) do not exceed 80% of the actual MAX WOT RPM you get for good engine life. For better life, keep it to 75%.

If you use the boat to tow people toys, then a prop that allows you, under the above test conditions, to slightly exceed the top end of the MAX WOT RPM range would be indicated. You would need to be cautious not to exceed the top recommended RPM when not towing people toys.

The most efficient solution would be two props that are changed based on the "mission of the day".

..." The most efficient solution would be two props that are changed based on the "mission of the day"."

Finally, someone saying what I have for years! Since boats lack a gearbox with multiple ratios inside, the only way to 'shift down or up' for today's load is with a prop change. And, hey, it ain't that difficult to do.

Jeff

It's and Alpha drive. No sea cock. He does not need to add gauges to his helm, it has a vessel View.

Put new batteries in it, put it in the water and run it. No special procedures.

..."He does not need to add gauges to his helm, it has a vessel View."

What's that, Chris?

Jeff

Apologies, I didn't mean to offend anyone with the "battery on concrete floor" comment, from my own experience over the years, learning the hard way, whenever I left a battery on the floor, it would discharge the battery .... keeping in mind the temperatures etc we have down here. I am sure the more modern batteries does not do this anymore, but like anything else, South Africa is way behind when it comes to technology ....

Anyway... thank you for all the responses, it helps alot.

I got 2 props with the boat, one is a speed prop and the other a power prop. Not sure of the pitch, they are also in storage. I would only be using the boat for wakeboarding and booze cruising so I will only be running the power prop and make sure I monitor the RPM accordingly.

Yes that is correct, it is fitted with a smart craft system, thank you for the link.

I looked at a few youtube videos on the engine I have and I keep hearing that you have to tilt the motor down when you start it etc. otherwise you can damage the bellows etc. Can someone please elaborate on that for me? What is a safe trim angle, because if I approach a beach where I would like to stop and swim etc, I would normally cruise in with the motor trimmed quite a bit up ....

With regards to the tell tale, is there a way to re-route the stream so it "pee's" out where you can see it?

You will learn how to trim your drive while driving.
The boat should be stored with the drive all the way down, Bellows are rubber and are not stretched out when the drive is down.

As far as a "piss stream" You do not need one. There is a water pressure sensor on your engine and a screen in The VV that will show you the water pressure.

If the water pressure drops too low or is too high it will set off the alarm and flash on the VV screen.

Fantastic, thank you for all the help. Can't wait to get her to the water!

re: "...Apologies, I didn't mean to offend anyone with the "battery on concrete floor" comment, from my own experience over the years, learning the hard way, whenever I left a battery on the floor, it would discharge the battery .... keeping in mind the temperatures etc we have down here. I am sure the more modern batteries does not do this anymore, but like anything else, South Africa is way behind when it comes to technology ..."

No one was offended by your comment. Further modern technology... modern batteries have plastic cases and better top designs so that there is less battery acid spilled on the outside of the case. When I first started "playing" with cars batteries often had marks on the outside from spilled battery acid. This residue, when rehydrated by damp conditions, is conductive to electricity.. drips on floor....etc. Cement floors unless sealed "wick" moisture from below... hence, I suspect the start of the "battery on the floor" meme. Also something to consider is that ALL secondary ( rechargeable) have a "self discharge rate". Newer batteries are better, old tech less so. Furthermore as batteries age, the self discharge rate accelerates. So, I'm not all that sure that a concrete floor ever had anything to do with batteries going dead... especially with newer batteries. Further aggravated by folks not fully charging a battery before putting away for the winter.

sorry to blither on... was going to work on my boat today as I'm off work and want to fish this weekend with my wife.... and it's pouring rain!

Hi guys, I ran the engine on muffs this weekend just to check out how it runs. Summer is coming closer and I want to get her ready. Runs great with no issues, one of the blower silver duct pipes needs fixing but I cannot actually see where the left hand one (standing in front of the motor) connects to the engine ..... I managed to locate 4 blue plugs to drain the engine, are there any more? Should the motor be completely cooled down before draining?

I read in the manual it is a good idea to tow the boat without the drain plugs so it can drain properly, but it will just go from the slipway into my garage, should I store it without the plugs? I would assume that the motor needs to be cooled down completely before I drain it after a weekends fun? I never had an inboard before so don't know the tricks yet. Can't find a reference to the silver ducting in the manual either, unless I didn't look properly ...

Draining a hot engine can lead to burns.

The "Silver Ducting" is never in any manual. They do not connect to the engine ( at least here in the USA per USCG regs). Typically, (per USCG regs) there are two scoops forward which at routed to the lowest part of the bilge forward of the fuel tank. Aft, there are also two. The one without the blower should descend into the engine compartment at least to the level of the engine's air intake. Typically, this scoop faces forward. The other with the blower (aft facing scoop), should route to the lowest 1/3 of the bilge ( but above normal bilge water level) and should be set up to suck out any gas vapors. Neither are connected, per se, to the engine itself.

Go to:

https://www.uscgboating.org/regulations/assets/builders-handbook/VENTILATION.pdf

and read more than you would normally want to...

Your silver duct pipes appear to the the ventilation ducts - one for inlet, one for outlet - usually with an inline blower. You won't find anything specific about them in the engine owners manual as they are the hull builder's responsibility....the generic mention in the engine owners manual will be the "ventilate for at least five minutes before starting" statement.

Thanks for the info guys. I got some new ducting yesterday so I will try and repair both of mine over the weekend. With regards to the draining ... I could only find 4 blue plugs, is this correct? So as far as I understand (please correct me if I am wrong) after a weekend of use, after I have taken the boat out the water, I should wait until the motor is completely cold and then remove all the plugs and store the boat with nose high up leaving the plugs out till next time? Keeping in mind that the temperatures here never go below 10 degrees celsius. (50 degrees F).

If it stays that warm all year, I'd suggest there's no need to drain anything.....a fresh water flush would be even better but would require some plumbing changes to make it easier....

If the boat sees the brine with frequent use, you can figure the exhaust elbows have between 5 & 7 years of life.....some get more, some get less but its still a good timeframe for budgeting....also figure on changing the water pump impeller every other year (nominally) and you should be ok...

Here on the "Jersey shore" where there are square miles of salt water bay with about 18 inches of water in it and not a few unexpected underwater lumps and shifting channels, (although we don't generally surf launch power boats) folks with outboards and stern drives find themselves replacing impellers annually. Routine fresh water flush expends elbow/manifold life.

At least you don't have our Chesapeake Bay 'minefields' (crab pots) to deal with!

Jeff

Nowhere as many as you do. Not really a hazard to navigation, but.... (see below)

http://www.conservewildlifenj.org/b...-crab-pots-removed-from-barnegat-bay-estuary/

Theft of crabs from traps a big issue...

I decided to buy a 21 feet boat with mercruiser 4.3 mpi......after all these years having all kind of outboards tested..driving planing......it has being to long since my last experience with sterndrives...last time it was twin volvo penta diesels at 93.....now as an experience engineer and 50 years old i came back and retried the sterndrive experience by mercruiser,,,,,,,,BOAT THAT I APROACHED HAD ONLY 150 HOURS AND IT WAS IN GOOD SHAPE THE PREVIOUS OWNER WAS A BOAT DEALER ,,,,,BUT LET ME SPEAK FROM HURT I WAS TOTALY DISSAPOINTED....MERCRUISER IS PRODUCINC JUNK ,,,IRON CUST RUSTY METALS FROM MIDLE AGE....EVERYTHING IN THIS COSTRUCTION IS RUSTED AND FAILURE.....YOU MERCRUISER PEOPLE ,,YOU ARE USING CAR PARTS IN SEA APLICATIONS ,,,,WHAT A BIG FAIL AND MISTAKE...WAKE UP AND SEE ALL AROUND YOU ANODISE ALOUMINIOUM AND ALOUMINIOUM FOR SEA APLICATIONS HAS INVENTED....FOR YOU MERCRUISER PEOPLE THAT YOU WERE MANUFACTURED IRON CAST MANIFOLDS AND RISERS ALL I CAN THINK IS THAT YOU WERE LOST IN MIDLE AGE......EVEN ALL YOUR PARTS ARE FUNNY LOOKING AFTER COMPARING WITH JAPANESE QUALITY,,,,EVEN ORINGS AND HOSES THAT YOU ARE USING ARE JUNK....CABLES ...EVERYTHING IS A BAD JOKE TO ME HERE.......LISTEN TO MY STATEMENT ...JUST HAVE A LOOK AT JAPANESE ENGINES AT SEA APLICATIONS AND START MANUFACTURING GOOD PRODUCTS CAUSE YOU ARE LOOSING CUSTOMERS EVERY DAY....I WILL SELL THIS JUNK CONSTRUCTION HALF PRICE AND GET MY SELF AN OUTBOARD BOAT AGAIN

now as an experience engineer and 50 years old
YOU MERCRUISER PEOPLE ,,YOU ARE USING CAR PARTS IN SEA APLICATIONS ,,,

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Ayuh,.... You should educate yerself before makin' stupid statements such as this,....

There are reasons japanese aluminum motors ain't used in I/O boats,....

No Torque, 'n aluminum corrodes faster than iron rusts,..

bondo said:

Ayuh,.... You should educate yerself before makin' stupid statements such as this,....

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He should learn the English language first.

And learn how to spell and work the caps lock ......

anyway ...... I took her out this weekend and she runs great! Like a champ, I was very impressed. I'm having a slight issue with the starter not kicking in straight away, I have to turn the key a few times before it goes from a solenoid click to the engine turning over .... I think it might be the terminals that is dodgy and a loose lug, I will replace that next time. Unless anyone has any other advice ... Another thing I picked up is the fuel gauge is not working .... there is a purple wire with white stripe and a black one coming from the tank under the floor and goes all the way to the smart craft system but there it sealed off with insolation tape. Does anyone know how I can test if the fuel sender is working properly? I want to get this working again as I don't wanto get stuck in the middle of nowhere .... no idea why they would have disconnected the fuel sender wires ...

I'm having a slight issue with the starter not kicking in straight away, I have to turn the key a few times before it goes from a solenoid click to the engine turning over .... I think it might be the terminals that is dodgy and a loose lug, I will replace that next time. Unless anyone has any other advice ...

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Ayuh,.... More than likely, corrosion is in play,.... Usually just removin', cleanin', ' reassemblin' All the connections is the cure,....
Start at the battery, doin' both ends of both cables,....'n don't forget the Grounds,...
I also slather a coatin' of grease onto 'em after to keep the corrosion from comin' back,....

Does anyone know how I can test if the fuel sender is working properly?

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Ground out the sender wire, 'n the gauge should peg to full,...