[noggino]

Just purchased a 1999 z222 with 230 hrs.the boat is equiped with a 7.4 mpi and bravo 3.I have taken the boat aout twice and love the power it has to push through rough water.My only question is why is 4500 rpm it on the big block!

[ShabahZ280]

Welcome to the board, and Congrats on the new purchase!

I've wondered the same thing, but apparently the WOT range on the engine itself is between 4200 and 4800. Mine only hits about 4400 with a Bravo I and a 21p stainless prop. I think they set them low so just in case you swap out props, you've still got a little room for fluctuation before maxing it completely out.

[Mike & Jayme]

Sounds like you have the same 7.4 mpi with the Bravo 3 as mine. We had our's out and around 5500 rpm's we were doing 60mph just starting to hit the rev limit. (Fast enough for me !!!!!) The pitch on my prop is a 20p so there must be some difference ???? Anyway ....i hope you enjoy your new boat....We do !!!!

[noggino]

Well the only thing im stupid on is on the props they have a 26 p on them so what is my pitch im thinking its low because the boat comes out of the hole great and tops around 52 - 54 .Thanks for the reply i have always loved mariahs since i was in my 20s and now i have one thanks.

[WetWilly]

Hi Mike & Jayme,

60 mph at 5500 RPM has me a quite concerned! We have a 96 Z240 Talari and we hit 62mph at 4700 rpm and we have the 7.4 w/carb Bravo III, 2.0 gear ratio outdrive and 28p props.

From what I can find, the the specs for your 7.4 MPI should be: WOT rpm is 4200-4600 for the 7.4 MPI and 4600-5000 for the 454 MAG MPI. As you can see, you're RPMs are way too high at 5500 indicating that the 20P props are under pitched for your Talari. Someone definitely wanted to get a better holeshot but I would say it's a little too much... I suspect you should be running a 24 to 26p props depending on your outdrive gear ratio.

I highly recommend you contact a Mercruiser dealer or service center and get their input about the RPMs your turning to insure your not damaging the motor by running it so high.

If you don't mind, let me know what Merc has to say about your max rpm.

Thanks,
WetWilly

[ShabahZ280]

I suspect the tach is reading wrong.... When mine was having issues, it read much higher. Knock on the glass on the gauge next time while you're driving. If you get any fluctuation, you've got dirty contact points and you'll have to clean it. It's very easy, you'll need to just get behind the gauge and cycle the 4cyl-6cyl-8cyl switch about a dozen times with a screwdriver. That'll clean the contacts and you should be back in good shape.

I believe Merc sets the rev limiter at the maximum end of the WOT range. So in your case, you won't be able to get much higher than 4600-4800 rpms without it kicking you back down. Especially if it's an MPI system.

[Mike & Jayme]

Hello again..... I will be calling Merc about the rpm's being high. I dont know if you know..... but i do have through the hull exhaust !!! Maybe that's why the rev limiter is @ 5500 ? or like shabah Z250 said ....the tach maybe off. I did have the local marina ck the boat from head to toe........and they said the boat runs unbelievable !!!!!! The boat does run super and I hope, i dont have a problem. Thanks......Mike

7.4L 454 Magnum MPI 385hp
Bravo 3 20p SS
Thru the hull exhaust

[indykoch]

Through hull's don't make any difference in rev limitations of the engine. I'd have to agree with Chris thinking there may be a slight tach reading problem. Mine did it in the past, and is starting to again. It's really simple, just turn that screw a few times and it's back to new!!

At 5500 RPM's, you'll soon have a hole in your sunpad... oh... about the same diameter as a 7.4L big block piston, coincidentally!!

Sounds like a great boat none-the-less!

[WetWilly]

Hi Mike & Jayme,

indykoch is right, the thru hull exhaust doesn't add any appreciable HP or speed as stated many times on the web. I'm sure your 454 is running tip top and hopefully it's the tach but I still think suspect the 20P props are too low in pitch for your Bravo 3. I found out on our last outing our speedo was about 5 to 6mph off according to the GPS, so that equates to a true speed of about 57MPH with 28P SS props on our Bravo 3 at 4700rpm. That to me is still pretty fast for a 12yr old boat.

With the right props your top end should be the same or higher at a much lower rpm while giving up very very little on the takeoff. That 454 Mag is a great engine and with 385 HP, your Talari can really fly!

WetWilly

[indykoch]

Woah!!! I missed that!! 20P on a Bravo 3?!?! Yeah, that's extremely low. But the rev limiter should definitely kick in before 5500. I'd check into both the tach and the props.