2000 Volvo 7.4 Gi

[bear_69cuda]

Hello,

Looking at a used boat, 22' V-hull bowrider.

It has 2000, 7.4 Volvo Gi with duo-prop drive

Engine SN:4012007348

Can anyone tell me if this is 300 or 320 hp?

And if this sould be good power combo in a 4000 lb boat?

Thanks in advance...

 

[Don S]

Re: 2000 Volvo 7.4 Gi

That SN is for a 7.4GIPEFS which has 310 hp.
Should see in the 40-45 speed range

 

[bear_69cuda]

Re: 2000 Volvo 7.4 Gi

Thanks Don,

I was hoping for 50-55 mph. would not top speed also depend on the duo-prop pitch?

I would assume it must have a good amount of low end torque...

 

[bear_69cuda]

Re: 2000 Volvo 7.4 Gi

How does the 7.4 GSi get and extra 75 hp? Cam? Is it MPI vs throttle body injection? or combo of both?

 

[Don S]

Re: 2000 Volvo 7.4 Gi

Lots of things are different between the Gi and the GSi. The max rpm is 5200 on the Gsi compared to 4600 on the Gi.
Different cams, different heads, probably different fuel mapping in the ECM, both are MPI, not TBI.
The gear ratio on the 7.4Gi should be 1.74, compared to a 1.98 for a 350. The GSi would go to 1.68.
you also don't go changing props like you do on a single prop drive. You get in the rpm range and that's it. The props are designed to work with each other, not like you can change 1 prop and leave the other the way it is. They come in very expensive sets. if you are looking for 50 to 55, you would need SS props (about $1400 about 3 years ago)

You would probably go faster using a newer 5.7 320hp MPI than going to a 7.4.

Oh, and those BBC, really like to suck down the gas

 

[bear_69cuda]

Re: 2000 Volvo 7.4 Gi

Hi Don,

Thanks for the clarification, on the engine, and duo-prop info... I see the GSi makes an 75 extra hp ( cam, heads, fuel mapping, etc...)

I'm expecting it to suck gas, but most of the time I like to cruise to a nice spot, relax, fish, and read... Every once and awhile, I like to hammer down, cruising a few min at WOT. This particular drive has 24 pitch props... Does this pitch raise my speed at all with 1.78 ratio in your experience? I'll be interested to see, what the actual WOT rpm are???? (excuse my ignorance, but gear ratio on an out-drive = 1.0 revolution on crankshaft spins the prop 1.78 revolutions, hence 1.78:1 correct?)

I'm still at odds why my deck boat with F150TXR Yamaha, that weighs 100 lbs. less hits 42mph GPS, and why this boat with 2 x the hp makes only the same speed? There must be a ton of low end, and mid-range torque in the 7.4 or something that will make this a fun combo?

Thanks again for chiming into my thread,

 

[Don S]

Re: 2000 Volvo 7.4 Gi

Drive ratio does nothing more than keep your WOT rpm in the most productive ranges of the props. No matter what size props you use, you have to be within the WOT range of your engine. On a DP drive, there is no tweaking of props to get most speed or most out of the hole. The DP drives weren't even meant for speeds exceeding 50mph. they were designed for hole shots, better fuel economy, and lower rpm to run at a certain speed, and they do that quite well.
Now, if you want to talk props, iboats has a forum for that, just don't forget. You need WOT rpm, and the proper gear ratio before props can do anything.

 

[bear_69cuda]

Re: 2000 Volvo 7.4 Gi

Thanks Don,

At $1400 for a set of props, I'll stick with the ones on the boat... So I'll need not start a thread regarding prop swap on iboats prop forum. but thanks for the reminder, I was driftin off topic. I may search then start a thread on opinions of this type of boat and power combo in general boating topics.

Are Bravo 1 and Volvo SX drives designed for more speed/rpm than the DP's design?

Thanks again boss!