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?