How finicky are the old HP500's?
 

How finicky are the old carbed HP500's? Some tell me that they are alot of trouble. I'm looking at a couple of boats with these engines but I don't want to be fussing with the motors every (or every other) time out!

Do they run on 89 Octane? Is it true that you need to re-do the upper end every 200 hours? Are the regular 502/415's more reliable?

Thanks

I had a pair of 98's.

one broke a lifter around 190 hrs, due
to the valve spring issue they had with
that era of engines, after that, ran them
another 250 hrs without any issue.

They run on 87 octane

Some say do the springs/lifters around 200 hrs.

Reliable ?....I'd say there as reliable as reg 502/415

I would have no problem owning them again.

I had one of the latest carb versions of the HP500. It actually had the updated springs. Had 175Hours. No problems. Run em like you stole it. Built to last, perfect start everytime.

Oh yeah, since there are 400+ miles of canals here in Cape Coral, we end up doing alot of idling...Is that a problem with these engines, you know, for like carbon build up or something...?

no problem very idle friendly

hp500 carb is a 502cid. at 200 hours the valve springs should be replaced and you can hear it when they haven't been. get documentation if they have been changed out. it cost me less than $1200 to replace the springs (on 2 engines).
your going to hear different opinions what to do after that such as going thru the whole valve train (topend refresh or even more) at +/- 500 hours or so, i'll cross that bridge when i get to it.
right now mine are running very well at 245 hours and are 10 years old.
i'm not a WOT kinda of guy but you do have to run them to keep the carbs cleaned out and yes i run mine on 89. they have a tendency to soot at idle (rich) so try to get the idle/mixture dialed in as best you can.
they are a strong engine nothing wrong with older technology.
good luck
jim

It is an excellent engine and I would not hesitate to buy a boat with them. As with any purchase, have them inspected,compression test, leak down, etc. You definately need to change the springs. Other than that, run the snot out of them.
Eddie

Upgrade valve springs at 250 hours. I did mine again at 420 hours and recently rebuilt car to pan at 600 hours. No issues ever. Idle smooth and run sweet. 600 hours before rebuilds is about as reliable as you can get I think. I love mine.


RAF

Yeah,
i can't wait to install mine 98 HP500s take outs, (70 hours on them!:D) in the Nordic. Just got find the time!
I think it's one of the best "Blue" motors ever built. I had 98 HP500 in my Velocity , and that thing ran like a champ all the time!
Dean

I've heard the same and also applies to the 500EFI and any other engine with 500+ HP. New springs/lifters around 200hrs.

mine were 1995 500HPs with 440hrs, ran excellent! just pulled them apart this past winter and they still looked new inside! very reliable and a better platform to build on than the 502-415

I had a twin engine 1999 38' Scarab AVS with over 400 hrs(flawless),sold the boat and the 2nd owner ran them another 2-300 hrs and I believe he still hasnt rebuilt them,but his mechanic told me they are now way over due.

changed my springs at 150 hours now have 527 hours did have to change 1 distributer and 1 water fuel pump assembly. haven't fired them up this year yet, hope to soon.:D

I fired mine off today! First time this spring. Heading out in the AM to SML.
Mine are 95's with around 275hrs. I did a top end job just before 200hrs. They both ran great, at that point,but I didn't want to take a chance. I changed everything in the valvetrain.
I run 89 octane, also.

My 98's had a valve lifter "issue". The tie bar between the lifters fatigues and breaks, the roller lifter rotates and breaks grinding cam in process. This happened at WOT in the middle of a poker run. Needless to say **** all thru the internals of that engine. I redid both engines with new style lifters and retainers and 525 cams, complete rebuild on problem engine. I have had to replace the power valves on the carbs. They fail and allow the motors to run way rich. But after 7 years and 500 total hrs I would buy these motors again.

I had a set in my last boat 2000 fountain No issues!

Had a pair in my 99 Fountain. Great motors as long as you tend to the valve train at the proper times. Upgraded springs solve these issues. As for the loading up on long idle periods, Merc has them set up pretty rich, warranty deal, but it is very easy to pull a jet size or two out and clean them up. I'd own them again, and wouldn't call them a fussy motor to own.

And its not that the valvetrain needs constant attention every 200 hours. It was the original valve springs that there was an issue with and it wasn't recommended to run them past 200 hours (if I remember correctly). If you have swapped to an upgraded spring, I wouldn't think you would need to change them every 200 hours from then on. Might be a good idea to pull a valve cover and give a good inspection though.

Mine run flawless as well. They start almost as good as an injected motor. I did have a problem last summer that appeared on the surface to be a lifter failure. Once we got the engines apart it seems that a stuck valve may have been the actual culprit. Either way, freshened both motors at that time and I haven't had a moments problem since. Actually, may be upgrading them over this coming winter!!!:cool-smiley-011:

Lots of great posts! Sounds like the HP500 is a wise choice!:cool-smiley-027: