450HP....pros & cons....
 

I'm about to make a move on a boat with twin 450's, I never knew there was such an engine, until I came across this boat. I have done some searching, & I couldn't find alot about this motor, other than, Merc on made it for a year or two, it is suppose to have the same internals as the 500. I didn't find anything negative about it, so I do hope that is a good thing :D. The motors have about 80 hours on a complete rebuild, & I understand that the "magic" hour on a 500HP is 300 before having to go thru.
So, I'm just looking for any info on this motor, what HP is it rated at, reliability, is it a solid tappet, or is it the hyd roller? Are the specs the same as the 500HP, other than the stroke?
I appreciate any input on this.

Is the seller able to produce any receipts for the rebuilds? How many hours before they were "rebuilt" I have seen a boat that got a new head gasket and valve job after an overheat that claimed a complete rebuild.

HP450....not 450HP....
 

Yes, he has all recipts, & rebuilds were done with low 300 hours, now the boat is at 410 hours. From what I hear the hour for HP motors is 300, before a "refresh", but I would assume that could be sooner or later, depending on how hard those hours were....just a guess though.

sounds like its time for a survey. Have the surveyor do a leak down test on the motors, at the very least a compression test.

I'm definetly going to have a survey done, I was not aware that the surveyor would go to that depth. I figured that would be on me to do for myself.....Sounds like money well spent...thanks.

Survey is the answer. Receipts are good too. As for the 450 HP’s… They were great. They were a 500HP built on a 454 block instead of a 502. Got to check the value springs ever 150 to 200 or so. Also understand the exhaust. Dry or Wet? Crossovers or water pump. That will tell you a lot more.

:DPat at AT built a 32 for a guy in St. Marteen in the Caribbean back in '96. Boat ran good and reliable..use to see it run over to Antigua and run the local races and then run back across the open Caribbean 100+ miles to St. Marteen.
Another friend of crb76 and mine installed some in an older Bullet and it would run within a couple of mph under our 32 Thunder with 502/465hp's with our dry exhaust. To this day I believe the 465's were the most wicked sounding motors. With or without dry exhaust. Dry was a must so they would last.
They hated them in Broward County either way..just ask Pat:D

A little off the 450's, but there's a low hour boat with the 502/465hp's that I've had my eye on. Other than sounding good, were they a pretty reliable motor? I just haven't seen many of them around. I've heard they were the precursor to the 500's.

Appreciate the info, they are definetly wet, & I see a water pump in the pics, so does that shorten the life of them?

As a matter of fact, this is a 96 Thunder that I'm intrested in. I really hope things all line up, & it works out.
It does seem that you just don't hear too many "bad" things about the HP motors. I'm looking for simplicity, & reliability......Carbs don't get much simplier (is that a word? lol)....

The 465's we had were prone to water reversion with the wet pipes. Merc kept doing head and valve warrenty work in the first 30 hrs. I was surprised with the Merc guys from the factory coming to look everything over they could not figure out the wet exhaust problem.
Doller Offshore installed dry exhaust for us and never had another problem.
In fact the engines went somewhere over 400 hrs. with the owners that I sold the boat to and they knew nothing of how to take care or run a boat of that type.
I did remove the water pumps and went to crossovers and then they and the boat really came alive. Needed to reprop then.

I remember the owner had problems with reversion/water intusion and that is why he had the engines rebuilt.

If you want to find out a little more about the boat, use the search and do an advanced search with the screen name faceoff. He used to be on the board once in a while and made some postings with some upgrades and minor issues.

What is involved to swap to a dry exhaust? I've only seen a couple of boats with the dry exhaust, & I did wonder how they were cooled.

That is exactly what he told me, he had a reversion problem, & that is what led him to the rebuilds. He says he has had zero problems since the rebuild, less than 100 hours ago.
Is it a head problem, allowing the water intrusion? Or too much cam? I saw the specs, here on another thread, profile didn't look all that radical, but I didn't see what the overlap is.

I'm not sure what was causing the reversion for him. He chased the issue for while and then finally just did rebuilds. The early HP500's had reversion issues also and Merc ended up changing the Gil risers to a taller version.

There are still double walled with water in between the walls. The difference is where they dump. Mine tails are basically dry. The tails run all the way though the transom and dump water right at the end. Other systems run a bunge off the tails and dump it through a fitting on the transom.

I was just thinking, I do remember him telling me he had new Gil exhaust put on. So is this something that would mean, I need to remove & inspect the exhaust every couple of years? That certainly wouldn't be that big of deal, if it would help prevent losing an engine to water intrusion.

I had to replace my Gils on the Pantera at 8 years old. The manifolds had internal hairline cracks. He may have changed to the newer style HP500 risers which should eliminate any reversion.

Got any current engine pics???

Yes, as a matter of fact I do, he sent me some over the weekend. I'll fire them off to ya this evening when I get home....I'm at work right now....uhhhhh....working......yeah, working....:D

[QUOTE=Griff;2293724]I had to replace my Gils on the Pantera at 8 years old. The manifolds had internal hairline cracks. QUOTE]

Do you think any of that was due to saltwater use? I guess, in a broader context, what is the expected lifespan of an exhaust package?

Water reversion was a cam issue on the 465HP. I never heard of it on the 450HP. If there was an issue it was either cam or vertical drop of the pipes from the elbow to the tip. Dry exhaust cures all of it. My dad, chuckbeecher would know how complicated it is to install dry.

[QUOTE=Shallow Minded;2293908]
Could be, but I do know that the previous owner always flushed well. The cracks were at the dividers at the tops of the manifolds just below where the risers connect. Most people get 8-10 yeras out of Gils from what I have read.

I felt the cam on the 465 was a little radical. Just stand next or behind one and reminded me of being up close and personal with a Nascar motor.
Doller also felt it was the drop to the transom.
Again, dry solved everything except noise.
We had no laws regarding it in Texas.
But i do remember a digruntled group at Shades on Lake Travis and flying bowls or salsa!!
But we were told to leave Broward County when the boat had wet.
They are just Bad Azz sounding.
If noise laws will be a problem for you I'd try some "cans" on the back.
A another friend had triple 465's in a Scarab with dry and no problems.
The Gills were O.K. but I'd change to some type of tubes or Stainless Marine. Gills are so old school.
By the way ours had little pisser tubes out the transom for each side of the exhaust on each engine.

Here is a pic of the engines, are these the taller version of the Gils?

Attachment 301766

Sounds like an awsome set-up, I may have to look into something like that. Coming from street rodding & drag racing....I love that sound....LOL....

Those are still the older style risers. They are most likely fine. I'm sure the owner ould have posted here if was having issues.

I appreciate the input, I'm definetly, very intrested in this boat. The owner has been quite upfront with me, & I'm sure if it was still an issue, he would let me know.
I just had not heard of these engines, & wanted to learn a bit about them. It seems, after reading thru all the input, they are a good, reliable engine, & as with any engine, ya gotta do the maintenance to keep em running :D.

A 32 with the the HP450's should run in the 75-76mph range.