Roby,
My engine is a Volvo Penta. I don't have the elbow between the throttle body and the intake. I also don't believe I have the "D" gasket issue, but I have never been able to spin more than 4600rpm.

I have heard some rev. limits are set at 4650, some at 4800. My Volvo Manual says 200 rpm above max. recomended rpm. I don't think I have ever heard my engine popping or loosing spark on a rev. limiter.

I also have a 25p Mirage plus, never got it over 4500rpm. The Mirage is faster than the Bravo. Maybe I need to barrow someones 23, might turn up more than the 24 Bravo.

Do you know how much air the throttle body on one of these will flow? I was thinking, mine would not go over 4600 because it ran out of air.

I'm not too sure about the Volvo throttlebody however you can figure the needed CFM by the following method:

cubic-inches X Max RPM divided by 3456 =

Roby

I have another complete 7.4MPI system from a Merc. sitting in my basement. Same throttle body as my Volvo. The only difference I see between the two systems is the elbow between the throttle body and the intake.

Using your formula: 5000rpm would only need about 650cfm...

Roby, I now that you have experience with fuel injection systems. Is there a way to figure how much the throttle body should flow? I believe it is 80mm round...

The CFM rating of any given 80mm throttle body can vary by a wide margin. However it should be plenty of CFM to run your engine. You are wanting to run your engine past 4600 RPMs and without knowing the exact Volvo Penta engine you have I can’t determine if you can.. or should.

The rev-limiter on the 7.4-MPI is supposed to be 4600 from what I’m told. Because of the limited flow of the Vortec heads and cam specifications, this engine isn’t going to make any power above that anyway. You might want to check with one of the prop experts here to determine the correct application for your hull & engine. You may get a couple hundred more RPM out of it by reducing pitch, but you may not be gaining any speed.

Best regards,
Roby

Hey Roby,
The Volvo engine I have is the same Vortec 7400 (L-29) base engine from GM that Merc. used. It's just painted gray rather than black.
I don't plan to run over 4600rpm for this year, but with off season mods., I am hoping for 4800-5000 for next year.
My plan is already in motion. I have a set of heads being ported, and new valves and springs will be installed. I have purchased Stainless Marine exhaust manifolds. I will be changing the cam to something with more lift and duration. Then I will need the ECU reprogrammed. I also have a set of larger injectors if needed.
My question is if the throttle body will flow enough for 4800-5000 RPM, or if I need to add to my shopping list.

Oh no for 5K RPM it should be more than adequate