496 maintenance in the Spring
 

I just bought my first big block boat last month,,,96 scarab 26 with a 2007 496 ho... I'd like to go over the whole motor this spring and just wondering what everyone recommends doing? The boat is winterized right now and didn't get a chance to change the oil before winter set in. So I will start with engine oil and drive oil, want to changed the engine coolant and also the cool fuel filter...what else should I be looking at doing?

Congrats on the new boat!
Search here on this site as their is a ton of info on winterizing and maintaining 496's.

If it were mine I would.......

Change engine oil/filter
Bravo oil
Power steering and trim fluid
Engine coolant
Plugs
Clean seawater side of heat exchanger and replace endcap gaskets.
Replace all filters in Gen 3 cool Fuel box. Examine for paint delamination inside cool fuel.box. known issue that can destroy your engine if not corrected.

After​​​​​​ having my fuel injectors tested and cleaned I would strongly suggest looking into this. 496's don't respond well to lean conditions.

Thanks for the reply! Are you saying the ends of the heat exchanger come apart? I see the big cartridge filter in the cool fuel box is there others as well? I have been reading up on that paint delamination, can you pull the fuel rails to see what might have gone through the system? The previous own thought there was roughly 100hrs on the motor but I'm going to hook it up to a computer in the spring to find out exactly.

The ends of the heat exchanger do come right off with those two nuts you can see. Be CERTAIN to replace the end cap gaskets. You will see why when you take them off (they deform). Getting to the block drains is kind of a PITA, but probably a little easier on a single engine boat. (They are back 3rd of engine, down low, above oil pan, below manifolds; a hex head IIRC.) Since you are draining the antifreeze anyway, just go ahead and remove the heat exchanger all together so you can inspect and clean it on a workbench. Before you drain your AF, fill your bilge with several inches of soapy Dawn water to dilute the antifreeze; so it's not so sticky all over you bilge. Then just drain it all out into a giant container for disposal.

I think the earlier cool fuel systems had more problems with paint flaking off than the later ones. You could pull all of your fuel injectors right now; and have them sent off for inspection, flow testing, and cleaning. Member "BUP" here on OSO is who I would send mine too, and he can answer any 496 question you may come up with.

I recommend owning and carrying a Rinda Technologies Inc. Marine and Industrial Engine Diagnostic Tools scanner for these engines. It's the best way to ensure that a $50 sensor doesn't ruin a month of boating for you in the middle of July waiting for a tech to see you & your boat.

Go ahead and replace your impeller in the spring too. You could take that apart now, and inspect the pump for wear. Just don't replace the impeller until spring.

Great information! Very much appreciated!. Sounds like i should look into getting the injectors done. I have noticed some rust on the front pulleys so I think I will be changing them as well. The boat has been used in salt but that's about the only rust i have noticed.

The GEN 3 cool fuel can be problematic. Also that cool fuel needs to be properly drained of all water for a proper winterization. Also certain runs of the gen 3 cool actually had 3 fuel filters internally. The paint is a huge issue with all Mercruiser GEN 3 cool fuel internally. The fuel rails can be a problem child with internal corrosion. The marine OEM's for the past couple of years are recommending fuel injector service every 7 years or less depending on how well your fuel samples are. Yes it recommended by the OEMs to perform fuel samples - bare min once per year.

To rephrase the GEN 3 cool fuel actually has 2 removeable fuel filters and a screen underside of one of the electric fuel pumps non removeable. That clogs as well.

Then certain runs of the gen 3 cool fuel even had 3 removable filters

I strongly suggest you have your fuel lines internally checked out for corrosion. Very common issue / 496 in salt water conditions. I can check them as well.

Where are you located BUP? I'm in Canada, sounds like you know your stuff on these motors....wish I come across draining the cool fuel during my winterization research because I did not drain that and I'm sure after these last 3 weeks of -15 C temps it did damage to it....

Thanks a lot for the info. Since I didn't drain the cool fuel I'm thinking about taking the unit off the motor. How do you tell if they are damaged from not being drained? Cracks on outside of the unit?

My cool fuel unit has the bracket with nut in the middle that holds the hoses on from the cooler. As I backed it off the top plastic fitting broke and straight antifreeze came out.. so i would say it was full of antifreeze so I may not have cracked anything but is that plastic fitting replaceable?

Got the module out of the boat and the paint looks new under the cover, filters definitely need to be changed, found a bumble bee in there as well. However 3 out of 6 of the bolts broke off getting the cover off. Dissimilar metals make lots of corrosion in the threads. Also going to see if I can tap the raw water inlets and put some threaded hose fittings in.

Mine also looked pretty good. Just one spot in the fuel pump side that looked to have bubbled a tad. I also broke a few getting the cover off. Should not have a problem tapping the housing. I am going to strip all internal paint and reassemble.

back side metal fuel line in the cool fuel needs a new quad ring for reinstallment - if not -- using the old quad ring -- the chances of leaking fuel is prob 60 / 40 that it will,

Also the rubber heat sleeve needs to cover that whole section of that metal fuel line (again back side of the cool fuel ) .

the special screw on the side section of the cool fuel -- the fuel line section is what holds the fuel line in place.

anti seize on the bolts and nuts especially for the bolts -- lift basket cool fuel.

the past 5 years the newer cool fuel gen III has a front lower side blue plastic drain plug. ( finally) actually this is how all the water gets drained out of the cool fuel -- hence why merc finally got it right and decided on that design.

this is the 4 gen design of the gen III cool fuel. The last one I did --- did not have paint internally.

Right on all good info and yeah definitely going to use some anti seize. I think I will strip the paint out of mine as well even though it looks good. I'm still going to pull the fuel rails to look for corrosion. What about the regulator does that see corrosion as well? I have been looking for a service manual and can only find them for serial numbers that start with OM.....
mine starts with a 1A

Many make that mistake about the regulator on the fuel rail . It was never a regulator --- its a fuel dampner. The regulatar is in and a section of it --- is on top of the GEN 3 cool fuel. On the gen 2 cool fuel the regulator is mounted to the water / fuel cooler.

The fuel dampner NEEDS to be very clean as well. The rails need to be spotless internally. Most saltwater boat apps - the injectors I see are contaminated internally with a form a corrosion collected internally of the injector and the micro basket filters are as well. . Aluminum oxide and so on. The 496 can be the worst at times and with paint from the gen 3 cool fuel internally. This is one of the reason why I get so many 496 injectors - I prob in the heart of boating season get 50 percent injectors are from a 496's. Merc and Volvo.

50 to 60 percent come from other dealers whom are their customers. They do not want to get into that end of the business flow testing and cleaning injectors. Its time consuming if one does that service fully and double checks everything plus maintaining the machines as well.

KEEP IN MIND with filtration including the internally basket filters for the injectors - its a fine line between filtering and flow - one can not have 100 percent filtration because that restricts flow - and one can not have 100 percent flow because that really offers not good filtration. So you have to have a happy balance of the 2. Flow and filtration.

^^ This. I choose to use Diacom software, but the point is the same.

Ok is that dampner something that can be taken out and cleaned? And I plan on buying a scanner of some sort but need to address the major this first. How much pressure is in the fuel pump cavity? I took the module to a machine shop and could not get the broken bolts out...they are in good...welded nuts on the ends and kept twisting off. Wondering if I make it work with the ones left...not ideal but just want to get it running for now

I have got the boat started on the hose but have not had it in the water yet, had a problem getting the fuel system primed but eventually got it with an outboard motor squeeze ball line to force it through the system....still waiting to get my interior back from the upholstery shop as well. But did hook the engine up to a computer. It showed that it had 100% power available, but 4 active codes came up.
91 pitot pressure low which i believe is common, 131 trim sensor circuit low, 75 fuel level 1 circuit high, and 191 fuel level 2 circuit high. Are they all normal codes or should I be concerned about any of them?

Normal. Your app is not set up for those. Mine scans the same codes.

ok great, thanks!

I seem to have a problem with the alarm buzzer or circuit for it. It's suppose to sound for about a second when the key is turned to the run position but doesn't every time. I first checked the main engine plug and that's all good, so then wanted to check voltage to it when I turn the key to the run position. There is a purple and tan/blue stripe going to it and when I put the volt meter from ground to the tan/blue the horn started sounding when I turn the key to run....so i left it for a few hours and then tried it again and no buzzer....put the volt meter on the tan/blue and then it started sounding again...its like the volt meter brings the buzzer back to life again...does it sound like the buzzer itself is going bad or something else?