496 HO...full impeller service, stainless pretty much the only option right?
 

Hey all,

Got my Donzi last April and baselined all maintenance. Thinking this year I need to replace the impellers and the housings. I have one engine that will climb to hit that 180 overheat alarm if I'm cruising for extended periods of time (30 minutes plus) at 4k. If I cruise at 3500, I never hit it. I'm guessing the impeller and housing is the first place to start right? Also probably buying new heat exchanger gaskets to have a look at that as well.

So that said, looks like the housings aren't the cheap ones I had on my 383s, but now it's the brass ones that run ~$350. So does everyone just do the stainless ones at $419 as the next step?

Anything I'm missing?

I did the rebuildable Hardin stainless on my 496. Worth the money IMO.

Those hardin gen 7 pumps with the removeable serp pulley are worth every penny of 550 dollars . If you have plenty of room ,to r+r the one with the pressed on pulley is fine also.
Thats for sure one case there where the quality will live on long after the price is forgotten

You might want to pull the fitting for the water supply out of a Exhaust manifold and stick your finger up there, this is the bottom one in the middle, don't just pull the hose. take it out. they can get pretty bad in 5 years or more. how old are they and is it a freshwater boat or salt?

http://www.offshoreonly.com/forums/g...eller-kit.html

On an unknown condition system I would backflush starting at the thru transom water hose. Flush each part individually as to not push crap further downstream. Pull the heat exchanger endcaps and clean. A .17 caliber bore brush fits the holes and stiff wire gets the end ones you can"t get to. Buy new endcap gaskets and o rings as they last about 3 yrs before they start sucking into the heat exchanger.

Link above shows another impeller rebuild option. I ran the Aftermarket Marine 496 kit all last season with no problems. If money is there then go for the Hardin Gen 7 kit.

What is your water pressure at:
idle?
cruise?
top speed?

You must know this before going forward.

My boat had 12+ seasons and 500+ hours on the original pumps (several impeller changes) and not one issue with water pressure other than typical worn old impellers. I did not have sea or sand strainers either. I don't see why so many people have had problems with the OEM brass pumps.

How old is your antifreeze?
Is it bright pink, or does it have a dark metallic color? Mercury closed cooling antifreeze is only good for seven seasons; eight max. If it's starting to turn dark, it is starting to silt up and not cool as well.

Have you opened, inspected, and cleaned your heat exchangers? Could very well have debris blockage in the tubes causing cooling issues. You were on the right track with replacing the heat exchanger end gaskets. Be certain to replace the grommets that go between the heat exchanger in the crossover as well. Those grommets are a trouble spot.

Another spot that is trouble is the transom tube thru-hull, they start getting mucked up and corroded and cut flow to the pump

Also, Capt. YARR...
...Does your boat have the Perko or another fresh water flush system installed? The Perko system has a spring loaded check ball in the "Tee" of the system that gets gummed up with debris (weeds, etc.) and does not allow enough water pressure though at higher speeds, which results in high temp...
...but cruising is fine. This is EXACTLY what happened with "Baja Rio" here on OSO's 30 Baja Outlaw with 496s. It's happened to quite a few others as well.

IF you have the "Tee" with the check ball in it, rip the spring and the check ball out. It's not needed.

It is an 06 35 ZR. It spent most of its life fresh water, a year on Lake Pontchartrain and now back to fresh water in Texas. Minus one super fun Texas Outlaw Challenge. :)

Boat was bought with 99 hours last year and I think I'm at around 130 now.

While changing my oil on the hose a few days ago they both were around 4 PSI at idle. I'll take some notes on the gauges over the weekend. I'd log both engines with my scanner but for some reason my scanner won't connect to one engine (thankfully not the one getting warm).

Unknown, it is pretty pink though.

I haven't opened them up. Buying the gaskets then diving in to that the weekend after this one. Wanted to make sure I got all the valuable tips before opening her up.

Checked out the water system pretty heavily yesterday chasing down a little leak (loose band clamp on Cool Fuel) and don't see any kind of flushing kit.