Budman,

See second time around and you get more info :D
I had a quick fix repair done to one of my hp500's to get me through the last month of a season. When I tore them down I found that the square port or whatever you call it gaskets had been installed which would duplicate the question your asking. I never noticed any difference in power. I also never really got on it that hard being it was the end of the season and I knew that one motor might be trouble if I did.

"second time around"
 

Scott,

Is that a thread title? Or a user logon? :confused:

Budman,

If you ran that carb on your dual plane it would be way too rich in my opinion. Merc. did some strange things with the stock jets. Pri: 81 port 75 starb. Sec: 89 port 93 starb. w/6.5 p.v. on pri. and blocked off on sec.

"OK, since my previous thread got blown away with the "Apache Thread Resurrection Debacle", I'll try this question again and see if I get any responses."

That is what I meant buy second time around ;)

I like it
 

Budman
I really like your set up! The exhaust valves aren't that important. You have an excellent camshaft with plenty of exhaust duration, I wouldn't bother changing the exhaust valves.
I really think that very few boat/engine combos will work with the 1.36:1 ratio. I have seen 500 HP engines run better with the 1.50:1 and I really think it is holding you back.
The exhaust manifolds are restrictive but also very expensive to replace. That would be your next investment though!
Make sure your ignition timing is set to 34 degrees total advance and use RV15YC4 Champion spark plugs gapped at .045 inches.
Try the 800 Holley with the stock jetting and see what happens but I am pretty sure that you won't see an improvement. The engine just doesn't need more carburetor than the Q-jet!
Put the 454 jetting back in the Quadrajet, it will be fine even though it was originally for a 330 engine.
Change the gear ratio and prop it right and you will have a nice combo (even without the good exhaust manifolds).
Sincerely
Dennis

I agree with Truckin!
You will need to optimize fuel mixture with any carb. If you need Q-Jet parts, Edelbrock has them. The gears in your outdrive are probably your single biggest problem!!
You can pretty much jet the Q-Jet with the secondary metering rods if you have the original primary metering in place. Be sure the secondary flap spring is correctly adjusted and this is a great carb!!

Thanks for the replies!

Scott,

As Homer would say, "Doh!" :D

Truckin',

Valves are not Inconnel, they are Ferea, but a step down from the super alloy. I have always had a nagging fear of reversion with the silent choice because of these valves. Manley does not make Inconel in a 1.72 valve, and I don't think Ferea makes the super alloy in that size either. Am I losing sleep over nothing?

I had plans to borrow BadDog's 1.5 Bravo with a 23 Mirage Plus this past fall, but rough water conditions cut our testing short. This would have been a nice test to see how much of a difference the 1.36 ratio is making. I know this subject has been discussed at length in previous threads, but to my knowledge no one has done any real back-to-back testing to prove it. Right now I am running a 21 Mirage (not Plus) with the 1.36, spinning it at about 4800 RPM at just a tad below 60 MPH. I have been told that I would have to increase pitch by about 2 to go to the 1.5, so that is why I am going to run the 23 Mirage Plus. Do you think it would be a better apples-to-apples comparison if I run a Mirage with the 1.5 instead of a Mirage Plus?

Blown1500,

I have an old 330 Q-jet laying around. Do you think I should just put the primary jets and rods out of it in my carb, and leave the 502 stuff on the secondary side? Any chance of running lean when I am just on the edge of when the secondaries start to kick in, like at part-throttle cruise?