Man I did a video on the flowpath of the water on the 496HO facebook group in December of '22. Can't figure out how to get a link here though. Are you a member of the 496HO group? Huge help for owners there.

87Mirage,

FB? Nope. I don't InstaGoogleTwitterFace anything. I'm starting to think I'm missing out on too much by not, but then I get over it. :rolleyes:

There's obviously a link function here on OSO, but sometimes things like FB links don't translate well.

I think I can see it in the drawings, but the whole system is not on any one drawing, so I'm struggling to piece it together while flipping back and forth from one drawing to another to another.

Send me a PM. I'll get you my cell and you can text it to me if you don't mind. I'll figure out how to get to it from there.

Thanks. Brad.

I don't think it has more flow or pressure, just more durable. They didn't recommend a strainer with your intercooler? Maybe you don't have to worry about weeds in your area, but we do in the Delta. BTW, Den-sure offers a larger heat exchanger, about $1,300. That would provide more cooling, but I don't think that will help your rising temp issue.

DonJuan,

I'm more of a mind that we've got a little something going on, as 87Mirage's witness shows the stock heat exchanger is sufficient with our minimal boost. Just gotta figure out what it is. Talking with Hilltop now about getting the impeller changed this week. We'll go on from there.

We don't have weeds so much in either of the lakes we frequent. Cumberland goes through a spring glut of debris, but Hilltop indicated the found no debris in the backflush. Is there potential for debris to build up in a spot that a typical backflush won't flush out?

Thanks. Brad.

The strainer is really to protect the intercooler. I would probably have them back-flush the system again from the heat exchanger back, remove the heat exchanger and flush it, make sure it has the correct anti-freeze ratio (it can actually be slightly more distilled water), remove and inspect the hose connection to the transom plate inlet, re-check and tighten all hose clamps, and have them check the 3/4" hose that goes from the exhaust manifold to the upper riser it it's equipped that way. Of course have them replace the impeller.

DonJuan,

Understood. I have really good output from the intercooler overboard, and it's not more than mildly warm after settling in from a hard run. I really don't think the intercooler is fouled at all.

The manifold-to-riser transfer hose is something I can check myself, and I will do that.

I refilled the coolant reservoir after replacing the reservoir after cracking it during our fuel injector ordeal. I used the prescribed 50/50 stuff, as is in the jug.

The rest I'm leaving to the shop that knows what they are doing.

Thanks. Brad.

I didn’t suggest that the intercooler would have debris in it. I was saying that most guys put in a sea strainer to protect it from weeds and I was curious why you didn’t have one. I don’t think your temperature issue has anything to do with the inter cooler. If you have a shop that’s competent and thorough, they should completely check the raw water cooling system to make sure there isn’t an issue.

DeltaDave,

DonJuan....? Same, same....?

The simple answer is that, when doing the initial build at PQ, they didn't install one, and neither of the two owners before me has felt a need to. We may address it moving forward.

Otherwise, we are working through the possibilities. I have faith in the shop. They've been around for decades.

Thanks. Brad.

I assume you are getting your coolant temp readings from the dash gauge?? Have you verified the accuracy of the gauge with a scanner or laser temp gun??

What year is your engine?? Is it compatible with Vessel View??

Read my previous post

Griff,

Yes. From the dash gauge. But I'm more concerned with the change I'm seeing, rather than the actual temp. 180° is not terribly hot, but it seems to be slowly creeping higher and higher as time goes by. I wouldn't disagree with the probability of a discrepancy in actual temp and gauge reading, even though it seems to be reasonably accurate. My main concern is that the boat USED to run ~160-165° as long or as hard as we ran it. At first, I just noticed that the temp would spike a bit after a hard run, which is what led me to install the oil temp gauge. But now it seems to climb up to 180° and hover there, so far to date, even if we are just mildly cruising. My concern is that it will eventually get to the point it is running over 200°, then over 220°, or may suddenly just run up and alarm out and shut down when we're at a highly inconvenient towed distance. My wife says I'm paranoid or looking for something to tinker with, but, truthfully, I just like to stay ahead of things that can ruin a weekend and/or checkbook.

Where would one take a more accurate reading?

The engine was built in 2001. I have no idea if it is VV compatible. The transom assembly says "SmartCraft" on it. Not sure if this is indicative or not. What would I look for to determine VV compatibility? Call Merc?

Thanks. Brad.

UnderPSI,

OK. Reread it. Care to be more specific? What to do? What to look for?

Thanks. Brad.

You can smoke a housing and impeller in 1 trip. Suck up some sand and groove the housing. I just put a new housing on my STRBD engine and it is significantly higher pressure. From 5psi before to 15psi now at idle.

Rookie,

I wouldn’t doubt that. Pretty sure we did just that a number of years ago in our Rinker at the party cove on Brookville lake. Never been back, and we don’t get anywhere near sand or gravel or anything such on either of the lakes we frequent now. I’m sure they will have a look at it when it’s apart.

Thanks. Brad.

BC - have you considered it may be global warming ? :evilb::grinser010::lolhit:

SB,

That you, Mr. Gore? :rolleyes:

Thanks. Brad.

I have friend who has a late 2001 build 496HO and he has VV mobile attached to his engine. Here is a link with a "contact us with your serial number to verify" VesselView Mobile (mercruiserparts.com)
I would use a laser temp gun on the Tstat Housing to check temp. That is where my temp sender is as well. Not sure if the 496 is the same though.
Have you ever changed the coolant??? Possibly getting weak and not cooling as effeciently??
Just throwing some ideas out there, but the first thing I'd do is verify the actual temp vs what the gauge says. I had to replace both of water temp gauges because they would act up and read high and act wierd intermittently..........and my gauges are the same as yours.

Griff,

Thanks for the link. We are heading down today and I will check when I get to the boat. Any idea where the engine serial number is located? I have been able to track it down through Merc from the transom ass’y serial number, but won’t have access to those notes until Monday morning. I suppose I could call Merc again….

I will acquire an IR thermometer and verify agreement between gauge and actual temp, IF I can get to it (intercooler may be in the way).

I have not done a full drain and replace, but the coolant reservoir was completely dumped in late ‘22 when I cracked the reservoir during the fuel injector ordeal. I could also tell some was lost when it was in the shop last, when they swapped the T-stat for a restrictor plate.

Thanks. Brad.

Your engine serial number on a 496 is usually on a sticker on the heat exchanger, starboard side of it. If not there it will be on a metal tag down near where the starter bolts on to the block.

Your temp senders are located on the crossover tube (where the heat exchanger mounts to). The sensor on the top of the crossover on the port side is for your dash gauge. There is another sensor on the starboard side of the crossover that is for the engine computer.

Are there any rubber hoses that could begin to collapse when softer as in temperatures go up? The wax pellets inside of the T-stat can slowly degrade. I am not familar with all the specifics of your cooling system but if your system is up to the task than you have a component that is beginning to fail. Revisit all of the basics and you will likely find your problem. Pick through each piece of the system, understand it and inspect or replace.

Pull the hose off the oil cooler. I found back flushing won’t get everything out. The oil cooler has a honeycomb center and I had to dig the debris out. The oil cooler is what the out flow from the sea pump goes to first. The claims bolt is 10mm.

You should listen to this guy. I think he is right. I know that I just went through this today. On Friday I took a ride and at the end of the ride the port engine went to 200° and the red warning light lit up. Fortunately , it was right when we were in front of the dock. I quickly docked the boat and turned the engine off. Both water pressure gauges were at very strange readings too. I called the marina this morning and the came out immediately. The guys changed both impellers. We went for a test ride and nothing changed. One of the techs had just been through a similar issue with a formula. So, he checked the gaskets at the end of the heat exchangers. He showed me the gasket. It looked like a big glob of black glue and was starting to break up into pieces. They changed all four. My son and I just took a test ride. Both the water temp and the water pressure are back to normal. Simple fix and took about ten minutes for all four to be replaced.

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