TomZ

iTrader: (2)

Tested my buddy's 26P Bravos... porpoising was better but I still had to sneak up on the trim. Not as bad but still an issue. I could only turn 4500 at 65 so if I went with the 4 blade route, I'd need to run at least a pair of 24s.

One thing that's been an issue... what I thought was bow steering isn't. With the boat trimmed up and running anything above 45-50 (wetted surface break is right under the helm chair) the boat seems to become vague steering-wise. Correcting causes the boat to want to hook in the opposite direction. This was even more prevalent with the Bravos.

There is very little, if any, play in the steering. Moving the tie bar with the power steering active, the tiller arms move with the tie bar with no play. Only seems to do this in smooth water... in rough water she does not exhibit this behavior.

I think it's the nose cones and maybe skeg related (I cleaned them up just slightly... they were a little dinged up... ordered Skeggards to make them original-ish for testing).

Give me some ideas guys!

Audiofn

Toe in a little or out? I would get inside the boat and grab the tiller arms and really pull up and down on them and see if they move at all. I would also check all the other connections inside. You may be at the point of swapping drive rotation... Mine loved turning in. It does not take that long if you have the correct stuff to do it. Like an hour or so. You need the gaskets and the oil passage seal and I always used a little RTV around the oil passage because some times that seal gets damaged when you install the drive. This way it won't leak drive fluid.

TomZ

iTrader: (2)

Jon, I should have updated this thread...

I did just that... tested everything vigorously. There was nothing in the steering that appeared to be loose. A lot of parts back there appear to be newer, and knowing the previous owner, I'd say that if anything was in need of replacement, it was taken care of.

I went out to the boat last week to get some things ready for an overnighter, and decided to knock the nose cones off the drives while getting other things ready. A few hits with a dead blow, and they were laying on the concrete. I took the boat out after getting them off... problem solved. The steering had a much more of a predicable feel running in the smooth stuff. In the rough she was no different. I still need to smooth out the lower unit, and I'll take care of that next week. I just ran out of time.

I still want to want swap out props.

Paul311

Hi Tom,

I can only tell I am experiencing the same issue/behavior as you do. I am running 26p bravo's. What i feel is that these props are typically stern-lifting, rather than bow lifting. This 311 (1989 is my model year) is set up for mirage plus props/bravo drives. These props are lifting the bow a more, or they don't lift the stern as much. While you need a lot of trim, basically too much trim with the bravo's to reach something near top speed, this causes an unstable behavior. It is very difficulty to drive a straight line and the boat seems constantly willing to turn either left or right. To my opinion this occurs while there so much trim, the drives are pulling the stern down again to get to bow up, this results in this unstable feeling and it consumes a lot of power also.
This behavior is not apparent with the mirage plus props.
The bravo's (stock) are ideal for cruising, but the design is not ideal in combination with the 311/bravo drive setup. That is what I think. Labbing can help.
I have HP500's a side, so the original 23p mirage is too less prop. By the end of next week I get a new set Mirage plus 25p, let' see what it does.

TomZ

iTrader: (2)

Your synopsis is pretty much spot on. I went back to the 27 Mirages from trying the 26 Bravos. Happier with the 27's but in the heat and humidity, they lug the motors.

I have a set of 25 Mirages going on tomorrow...

Paul311

Let me know your findings..

TomZ

iTrader: (2)

I didn't get much seat time after the prop change; deterring factors were weather, and a pretty bad jellyfish incident with my daughter. What I did find was that the boat planed no differently than compared with the 27's, and porpoising seemed to be a little less. I might be able to do some testing this weekend; we'll see how the schedule works out.

Redneckcustoms13

I hope your daughter is ok. It's kind of surprising that the same props just a slightly smaller pitch can make a difference in the porpoise. Maybe the torque of the engine at different rpm? I'm planning to tear down tonight (fingers crossed). Any updates on your a.c. plan?