Bravo II to Bravo III Conversion - Maxum Boat Owners Club

GentleMan · 08-01-2016, 03:30 AM

Hi everyone, trying to get an answer if it's possible to switch to Bravo 2 to Bravo 3 without any fuss or having to change all the setup on the transom. I own a Maxum 1998 SCR 3000 with mercs 4.3L of 190hp each. Some say the switch is easy, simply take off the 6 bolts and the bravo 2 drive and put the bravo 3 drive and it fits like papa into mama. Others say you can't do it , ratio and all and most of all the cost ain't worth it, the better idea is to change the boat for more hp. So can somebody help me? Thanks.

Steph.

mmwjr · 08-01-2016, 12:09 PM

welcome aboard

Yes all Bravos use the same transom assembly so a B3 will bolt right on. The drives will need to be geared for the 4.3s but that should not be an issue as Merc sells that combo as a package.

All Bravos use the same upper housing but the gear ratio may not work with you engines but if they do you would only need to swap the lowers.

BTY starting 2 threads on the same topic will not provide you any more help.

shrew · 08-01-2016, 04:43 PM

What are you attempting to gain with this upgrade? The outdrive won't add HP.

shrew · 08-01-2016, 04:50 PM

Also, are you sure you have BII drives? The Mercruiser 4.3 only pushes around 220 HP, which will be well under the 300HP limit of an Alpha drive, which is what I see more frequently paired with a 4.3. Bravo's get into much higher HP and max speeds.

I honestly don't even see a need for a Bravo drive on that setup at all. The benefit of duo-prop won't be as noticeable on twins.

GentleMan · 08-02-2016, 01:39 AM

Sorry about the threads, kind a new at this and the first time I posted my comment I taught it didn't work. Even had to ask my wife to help me. I'm a big goofy with computers.

GentleMan · 08-02-2016, 02:11 AM

Thanks Shrew. I'm disappointed to read your reply dough cause I really taught adding more props would help gain more mph on my cruising speed. My two B2 props are made of aluminium (pitch 19) and have been repaired a couple times. Spoke with a Merc consultant and he suggested a 17 pitch to see if there were any significant changes, before even considering the switch for B3 drives. I have no idea if stainless props would make a difference. I feel like my boat is to heavy for my 4,3L. I can hardly reach 4400 rpm with both sticks fully dropped down, sounds like my motors are crying to get out of the engine room and say:"So long Pal". My top speed: around 23-25 mph. So very disappointing. Can hardly follow my friends (5.0L with Volvo duel props). This calls for a serious talk with my financial manager (wife) LOL! Thanks to you.

mmwjr · 08-02-2016, 02:17 AM

Quote:

Originally Posted by GentleMan

Sorry about the threads, kind a new at this and the first time I posted my comment I taught it didn't work. Even had to ask my wife to help me. I'm a big goofy with computers.

No worries.

mmwjr · 08-02-2016, 02:22 AM

Quote:

Originally Posted by GentleMan

Thanks Shrew. I'm disappointed to read your reply dough cause I really taught adding more props would help gain more mph on my cruising speed. My two B2 props are made of aluminium (pitch 19) and have been repaired a couple times. Spoke with a Merc consultant and he suggested a 17 pitch to see if there were any significant changes, before even considering the switch for B3 drives. I have no idea if stainless props would make a difference. I feel like my boat is to heavy for my 4,3L. I can hardly reach 4400 rpm with both sticks fully dropped down, sounds like my motors are crying to get out of the engine room and say:"So long Pal". My top speed: around 23-25 mph. So very disappointing. Can hardly follow my friends (5.0L with Volvo duel props). This calls for a serious talk with my financial manager (wife) LOL! Thanks to you.

I would try the 17" pitch that was suggested as it will allow for higher WOT as well as faster to rev up. Going to SS props from alumium you have to drop the pitch as they are heavier and do not flex as much all of which loads the engine down. I have heard others here with the 4.3s in that model and have the same complaint. 5.0 or 5.7 would be a great improvement or buy another boat powered that way. Also big cruisers are not speed demons and 20s to low 30s mph is normal.

shrew · 08-02-2016, 02:13 PM

I ran through the Mercruiser Prop calculator and 19" is what it spit out. I would try it for yourself. I don't know the gear ratio for your drives, so I used BII (2:1).

https://www.mercurymarine.com/en/us/...tor/#/step-one

The engine should be in the 4400-4800 max rpm range. Drives all the way down is going to cause some issues. I would click the drives out as high as they will go without cavitating. Then see what the max rpm is.

speedysprocket · 08-02-2016, 03:25 PM

Quote:

Originally Posted by shrew

The engine should be in the 4400-4800 max rpm range. Drives all the way down is going to cause some issues. I would click the drives out as high as they will go without cavitating. Then see what the max rpm is.

My 3200 goes fastest with the drives all the way down. As I creep them up, I lose speed, and it doesn't take going too far up until they cavitate. I also need to keep the boat going about 25 mph or more to stay on a decent level plane without using the trim tabs... I have 7.4Ls and generator; is this just results of a heavy boat?

shrew · 08-03-2016, 02:16 PM

Thereotically, the further the drives are out the less hull you have in the water and less drag due to friction. This should translate to higher speeds. Granted, you only have approx. 6 'clicks' out on the drives before you hit the trim limit. I start cavitating around 4+ clicks unless it's really calm.

I use trim tabs very actively. I'm frequently adjusting them. Though once I set drive trim, it frequently remains there unless I get into either rougher or calmer water and can trim it in or out more.

GentleMan · 08-04-2016, 02:40 AM

Well thanks to all of you, I'll give it some thoughts. I guess the first step would be trying B2 propellers with 17" pitch. I'll get back to you on the result.

Steph.

GentleMan · 09-18-2016, 02:43 AM

I learned speaking with the owner of my marina who grew up around boats and started around the age of 10 "driving" them, first step is to find the right angle (clicks as you say) of the drive and then finishing with the trims. After 7 seasons now on the water, I just found that in my case that notion came pretty handy. Eyeballing my GPS speed indicator in the process allows me to find my top speed and the best combination. I definetely agree that now it's part of the process to reach a better top speed, more confort and probably saving $$$ on fuel