Re: 61.6mph at 4800rpm but it cost me
 

thats great oil pressure at Idle ....Have you noticed after a hard run what it drops to at idle ? Normally it will drop but come back within a cpl of mins .

Re: 61.6mph at 4800rpm but it cost me
 

I agree, high oil pressure is an over rated thing. Flow is much more important than pressures through the roof. 20 pounds at idle, especially warm, is fine. Actually, 10 pounds is fine. But, everyone wants to see idel pressures at 60 friggin' pounds. Totally unnecessary.

My motors were totally rebuilt last year. Pre-rebuild pressures were about 20 lbs idle and 45 at speed. After-build pressures are about 20 lbs idle and 50 at speed. We put in high volume pumps and didn't worry about producing gobs of pressure. Flow and cooling, that's whats important.

Sometimes, low pressures can be indicative of wear or excessive clearance. Usually, other performance indicators appear before you see low oil pressures, like smoke, steam, rough idle, low rpms.

The most common thing (in my experience) needing freshening or rebuild is the heads. Oil pressure will tell you nothing about the condition of heads/valves/etc. The lower ends of both of my engines showed little or no appreaciable wear. Bearings were great, replaced anyway of course, but still great. Rings were fine, cylinder walls great, just a quick hone to "scrape" 'em up a bit was all that was needed. However, my heads were basically shot. Fine cracks in three out of four. Valves not sealing. Bought new Iron Eagles, fully assembled and slapped them on my cleaned up blocks, good to go. Now, not a single wisp of steam from my exhaust and it runs and idles very smoothly.

Actually, even with my clapped out heads prior to rebuild, I didn't sense any performance loss. Just lots of steam in my exhaust. That bugged me so that's why I rebuilt the engines.

Re: 61.6mph at 4800rpm but it cost me
 

That's great oil pressure when hot. If the oil pressure gets lower as the engine gets older, it is almost assuredly worn out bearings. Any blue smoke, other than at start up almost invariably indicates worn rings. I agree with ThirdBird that the heads and/or valve train are a whole lot more likely to go bad first, especially if you keep clean oil in an engine.

Re: 61.6mph at 4800rpm but it cost me
 

Mine does the same thing after a hard run. When I bring it just above idle, the pressure comes right up. I'm wondering if it's not the oil frothing. :confused: I tried synthetic oil with the same results.

Re: 61.6mph at 4800rpm but it cost me
 

Well after running it hard today, looks like mine do the same as everyone else: low psi afterwards. The port motor still holds about 15-20, but that starboard motor dropped to 10psi. And after a while they came up.
But now that ThirdBird mentions it, I think there's a little steam coming from the starboard motor. Kinda hard to tell since I'm by myself, and I have the Silent Thunder platform. The starboard motor also runs a little warmer (5-10degrees), but I think that pump is on it's last legs.
Even worse than that, but perhaps related, the starboard motor seems to have trouble making psi at high revs. Turned it to 5000 today and saw that I wasn't getting much over 40psi. I've always figured on the 10psi/1000rpm rule, so I freaked. But it seemed to still make around 40psi everywhere below 4500 or so, so Idon't know what to make of it. I really want oil temp (and water psi) gauges. I wouldn't run without those in the race car, so why not have them in the boat?
As for my new props, not impressed. 22P Q-IV X's from Hydromotive. Yeah, I got a couple hundred rpm more, but only a couple mph out of 'em. And not much of an increase at midrange either, maybe 3mph. I tried to tell them that everyone is running 23P (or more), but they said to start with these (besides the fact the 23Ps werent in stock). So the 23P Mirages go back on and I'll look for bigger Hydros in a week or so.
I know I'm gonna dig into these motors sooner or later (or buy another set altogether), so I'm not sure which props I should get. I probably wouldn't build/buy anything more than 450hp or so? I'm not poker running, or racing, I need a good mid-range pitch.
Thanks,
Michael

Re: 61.6mph at 4800rpm but it cost me
 

Pressure (PSI) is resistance to flow. For a given systm of plumbing more flow will equal more PSI. Joe Murray