357 Mag Bravo 4V Reman, Just Installed, 325HP, WORSE then old engine @ 260HP!!! ??

[Orbitter]

So been a while, but ultimately I really have not found out for sure what the issue is.

I would assume I could rejet the carb to improve bottom end a little but at this point
I am blaming it on the engine tuning from Merc!
I think that the engine is tuned for max power and Merc sacrificed bottom end torque to attain the 325HP figure.
But without hooking it up to a dyno or obtaining the elusive dyno graphs from Merc, it's impossible to say.

I have since put 24 pitch props on it and it's working better but still is very slow to plane.

Until I get more money & time to rejet (Actually I think my next step is a new intake system)...

Until next time

Best Regards,
Bryan

 

[tank1949]

As the Doctor ordered...you need to down pitch to about a 18/maybe 20...Or add about 500hp and that aint cheap ya know what i mean...:laugh:

Sounds like 26" prop on it now, was same for 350 260 HP motor. Perhaps not... Also sounds like whoever set timing may have screwed up. If it is not advancing (you can test with light for advance) then motor will be weak. I assumed you used existing ignition from 260 hp motor????? Please check to see if ignition advances. If it does, run compression on it. If new motor is under warranty, let them FIX IT!

 

[HT32BSX115]

I have since put 24 pitch props on it and it's working better but still is very slow to plane.

Until I get more money & time to rejet (Actually I think my next step is a new intake system)...

Until next time

Best Regards,
Bryan

Bryan,

Watched your video again and I noticed that you don't trim during acceleration. I thought about that a bit and seem to remember that if I start out with the drive trimmed all the way IN, and don't trim its a LOT more sluggish out of the hole. I usually trim OUT a bit asthe boat accelerates. You may also find that FULL-IN is really too far IN for any regular operation.

I also seem to remember that there are different IN limit blocks that prevent you from trimming in too far (ever) there's a service bulletin about trim limits for safety purposes that can be different for different boats.

None of this is relevant if nothing has changed (incl the props) from when you had the previous engine.

I still think your problem is induction (fuel mixture etc) or timing (and I wonder if the cam timing has been a tad off from the start or the module is stuck in BASE mode etc?)

 

[Orbitter]

So, I probably didn't in the video. I have since found that trimming full in actually makes a slight vibration if left full in.
After I'm up, and sometimes before I'm up, I usually trim out just a little. Hold the trim button for like .5 seconds.

It actually looses RPM if I trim full in. I have to trim out .5 to 1.5 seconds and I can see about a 50rpm increase when on plane.
It may be that the trim limit is set incorrectly, I just don't know enough about it. You are welcome to school me.

 

[HT32BSX115]

So, I probably didn't in the video. I have since found that trimming full in actually makes a slight vibration if left full in.
After I'm up, and sometimes before I'm up, I usually trim out just a little. Hold the trim button for like .5 seconds.

It actually looses RPM if I trim full in. I have to trim out .5 to 1.5 seconds and I can see about a 50rpm increase when on plane.
It may be that the trim limit is set incorrectly, I just don't know enough about it. You are welcome to school me.

Howdy Bryan!

It's been a while so you'll have to refresh my memory on what you have this engine in....... It's a Bravo III in a 21-24ft boat?

What is your drive ratio? (1.81:1, 2.00:1, 2.20:1?)

That's sort of important and will determine if a 22p, 24p or 26p propset is right.

Most boat manufacturers pair a 2.20:2 or 2.00:1 (Bravo III) drive with an SBC. My 1.81:1 drive (7.4L) came out of a 1998 24ft Bayliner Cuddy that weighed a tad more than my 21ft Four Winns

Also, I ended up changing the IN-Limit on my cyls. Mercury is fairly adamant about being very careful how this is set up because the wrong in-limit can make the boat uncontrollable.

It's discussed here: ---> Here

 

[Bondo]

So, I probably didn't in the video. I have since found that trimming full in actually makes a slight vibration if left full in.
After I'm up, and sometimes before I'm up, I usually trim out just a little. Hold the trim button for like .5 seconds.


It actually looses RPM if I trim full in. I have to trim out .5 to 1.5 seconds and I can see about a 50rpm increase when on plane.
It may be that the trim limit is set incorrectly, I just don't know enough about it. You are welcome to school me.

Ayuh,..... What I've found, pretty much with All of My boats is,.......

To launch, trim full down, 'n drop the throttle,.....

As the bow starts to drop, hit the up button, 'n when it breaks over onto plane, start tappin' the up button til ya got the hull, Flyin',.......
When the last tap causes it to porpoise on ya, then tap the down button to stabilize it,....

With any luck, chine walkin' won't happen as all this is goin' on,......

Worst Scare I ever had was in an ole Glastron Jet-Flite, with a 135hp Tower of Power,.....
Hooked a chine on a random wave,..... 'course, that thing was pretty chiney most everyday,....

 

[HT32BSX115]

Howdy Bryan!

It's been a while so you'll have to refresh my memory on what you have this engine in....... It's a Bravo III in a 21-24ft boat?

Ok....So I went back and looked at earlier posts in this thread! For some reason All I saw was page 3 in the thread.

Not positive but, it says "Serial Number 2.20R 0L********"
I'm guessing that means 2.20:1
It's stamped in the drive right near the top on the port side.

You said you have a 2.20:1 drive You can verify it 2 ways............ by reading the ratio on the side......the other way would be to turn the engine by hand (plugs out) IN GEAR with a wrench. ..Turn the engine 22 turns and have someone count prop turns.......... 22 ENG revolutions equals 10 prop revolutions. 2.20:1

You could also turn the engine 2.2 turns (2 full turns + 0.2 turns) 0.2 is 72 degrees (0.2 x 360= 72degrees) 72 degrees is a little shy of 90degrees.....or 1/4 turn......and probably more than close enough to verify. For a 2.43:1 drive 0.43 is a little shy of 1/2 turn.

2.00:1 is easy. turn the engine 2 full turns = 1 prop turn.


It's possible that someone had that drive rebuilt using different gears ........ This will drive(pun intended) you nuts because you're propping for 2.20 :1 when it's in fact a 2.00 or 1.81 drive You don't have a LOT of excessive HP to play with so you have to get the propset right for your ratio.





A slightly high ratio drive will make it seem like the engine is not developing full HP. You need to KNOW what drive ratio you have so you can put the right prop pitch on it before you start looking at engine problems. Also, looking at your previous spark plug soot etc, if that carb is jetted too rich, or your timing is retarded, (like we said earlier) it's going to be a "Dog" outta the hole.....

Ayuh,..... What I've found, pretty much with All of My boats is,.......

To launch, trim full down, 'n drop the throttle,.....

As the bow starts to drop, hit the up button, 'n when it breaks over onto plane, start tappin' the up button til ya got the hull, Flyin',.......
When the last tap causes it to porpoise on ya, then tap the down button to stabilize it,....

This is EXACTLY how I do it in my Bravo III powered Four Winns!