500efi's
 

I am about to buy a 2000 donzi 33zx with twin 500efi's that have 324 hours on them. should i be conserned about haveing to rebuld the topend sooner then i would like? the compreshion test came back good.

I just rebuilt my 500 EFI s in my 02 Top Gun with 375 hrs

I have someone check spring pressure on them. You may get a few more hours out of them.

The top ends are about due. The longer you wait, the more risk of a failure that could cause more severe damage.

Can someone explain why @ 3-400 hrs. these motors need rebuilding? Lets say that you drove the boat at WOT (5000rpms) for that 400 hrs that would still only be around 24,000 miles on a car. I have built a couple of hi-perf motors before, I just don't get the low hour rebuilds.

Think a car engine running at 5,000 RPMs will last 24,000 miles??

one word - load
boats put 10x the load on an engine than cars

Not rebuilds, top-end freshening up. Heads rebuilt (valvesprings, guides, seats, etc), check pushrods/lifters, and they should be good for awhile.

I did a set last year that had 450 hrs, and the thing
that was the most obvious was the head gaskets.....they
were pretty much toast between the cylinders.

:ernaehrung004:Congrats on the boat, I would definitely consider budgeting for an upper Valve Train - Refresh, its much cheaper to do it "ProActively" then after words... I had a roller lifter crack in mine and it locked up the cam shaft and basically I had to rebuild the whole motor - needle bearings went everywhere... mine was a freak thing...and only a couple hundred hours...but they are great motors....

New motor is running strong and back in the little Donzi to get me to the Reindeer Games later this season....

At least get a leak down and compression check on the motors as is...and have an experienced Merc or Motor Guy look them over... its worth it...

Those are great motors in that boat...really wake it up compared to stock offering of that vintage...

Good Luck

Danny :angry-smiley-044:

Nobody drive their boat at wot @ 5000 rpms for 400 hrs with 500EFIs. If they did, the 500 would probably be done for.

Don't even consider this comparison! Boat and car engines, as mentioned earlier, are two very different things in every way. 300-400 hrs is about the limit on any high performance motor of this kind. Some say 10x the hours, but it even be more. Mercs blue motors need rebuilds, as any other high perf. motor, that's how it is. Not exactly sure why you are asking this question? Nothing rude meant, just curious. If you want to go blue, it'll be something you'll need to put money into over time.

Good luck with the new boat:)

thanks for all the info. and the reason i am asking is because i am spending 55k on the boat now so i was hopein what i was hearing about the hours time frame was off a bit. i love the motors and dont mind getting it done was just hoping it wouldnt be in the first season with the boat.....

This would be my concern as well. And if you're going to go through the hassle of pulling the heads you might as well do a valve job. Then you'll be good for a long time.

they will go 500 hrs with nothing more then oil change.... at 500hrs you are on borrowed time

dose any one know what the top speed for a 33 ft with twin 500s would be.

x2

If compression is strong, I would run it through the summer and consider the top end rebuild a winter project. I ran my last 500 efi to 410 hrs with no problems. I don't run wot for more than a minute or two .

here i am with another question. the boat i am getting has the 500 efi's with bravo x drives. are those drives going to hold up or should i start saving for xr's?

Mid 70's on the speed. I have a Daytona edition with the extension boxes, and labbed props and the best I have seen is 82.

I would definitely be using the "top end needing refreshning" as a bargaining chip when negotiating price on this boat.

One thing to look at on these HP500efi's will be the number of hours @ 4500 rpms and above. This will be generally a critical factor in how weak the valve springs and valve train in general. Another factor will be what type of issues if any the engines had during that 350 or so hours, ie., overheats, overspeeds, loss of oil pressures, etc. if known or divulged as well as records of oil changes and services. Lastly, obviously generally fresh water use with good maintenance will generally deliver engines in better shape than their salt water brethren. Head gaskets seem to be a problem area because of raw water and it sure would have been nice if Mercury Racing had used the Cometic type MLS stainless head gaskets , better valve spring materials and high volume oil pumps in those engines also.
My opinion is that when making offers or buying boats with these engines that have 250-300 plus hours without top end refreshening the pricing should reflect the need for this and you need to be very careful going to the 350-400hour uses with untouched engines you don't know all these exact factors and a dropped valve or serious head gasket failure in any engine can be catistrophic and expensive.
Sincerly hope everything works out well and safe for you, they are in general very good engines as time has proven.

Best Regards,
Ray @ Raylar

i did use it to my advantage. he was asking 62k for it....i dont think i did too bad.

i had the boat surveyed on friday and the guy that did it told me it ran 80 on gps during the sea tryel so i gess thats good

Looks like this is your boat?...nice!

http://www.powerboatlistings.com/view/15464

yup.......:D:D:D:D

Yes, these boats should run low 80's, depending on the elevation & water type. I think the factory's spec was 83-84 MPH in saltwater. My dad has a 2000 w/500's & regular B1's and it easily hits 80 in TN.

I have 300 hours on my 5000 EFI's and I'm have the Top End done prior to the start of the season, rather be safe than sorry. I'll know in a week or so how everything looked.

ok cool.

douse any one know if all donzi zx's are set up to spin in wards or is that more geared to the motor and drive setup? also if it is set up like that douse that make docking harder at first? im going from a 26 single to a 33 twin.

My dad's props were put on wrong, spinning outwards, and docking was pretty easy. We switched them to spinning innwards but have yet to run the boat again. It'll be interesting to see how it behaves around the dock. As far as I know all the boats were set up to spin innwards.

sweet ride

On average, or as a range, how much should one expect to pay, per motor, for a top-end refresh on a 500EFI?

Yes they were all set-up to spin in from factory to get more lift. Makes backing up much more difficult can't just use sticks as with most twins.

Ok now i have noticed on a lot of big powered boats there seems to be a water dump out the on the sides or back of the hull for the motors. On my boat the holes are there for it but nothing is hooked up to them. I have the 500 efi's and i was wondering douse my power package not need it or is it something i should look in to hooking up? :confused:

I wouldn't say ALL boats were setup to spin in. It depends on the boat, x-dimension, drives, etc. Not ALL boats are the same.

Superchargers w intercoolers

oh ok must have been there from the factory. will then i gess i will have to look in to some Superchargers then.....:evilb: there like $200 right :lolhit:

Top End is complete and engines are back in the boat. What the engine builder told me was that the head gaskets were shot and I wouldn't have gotten another season out of them, he also said that he tested all the valve springs and could find one that was within spec, all were weak, none were broke or cracked though. This was all done with 292 hours and easy hours in my opinion. So if you run your boat hard or do a lot of poker runs I'd be looking to tear into things sooner than I did.

If u dont mind me asking. what was the cost per motor so i know what to expect. even a round a bout would work. just for an idea. thanks

so every 2 1/4 years I'd have to rebuild damn!!!!!!!