Driving with full bracket

peterb · #1 06-11-2007, 03:59 PM

My new old boat has a full size flotation bracket w/twin 200 HP engines. That's a lot of weight back there. The boat is subject to a bronco like ride unless I put the trim tabs all the way down. Also, I am finding that the ride is better when the engines are trimmed down as well.

Lastly, i was told by the surveyor that I could further improve the ride by raising the engines one to two notches. I would be very interested to hear how other boaters with flotation brackets have optimized their rides.

Peter

eggsuckindog · #2 06-11-2007, 07:37 PM

On engine height, if the cavatation plates are too low they will cause a porpoise like effect, maybe a pic of the engines level and some sort of straight edge. As I just posted to another thread, I think the formula is 1" above the hull bottom for each 12" set back. Most engines in general are set up too low and getting right really helps the drive ability

Bushwacker · #3 06-11-2007, 11:49 PM

Don Herman installed my motor per the 1"/1' of setback formula. I have since been able to raise motor 2 holes with no handling/ventilation problems; can put helm full over at 25-30 mph, no problems. Boat will tend to porpoise if motor is trimmed too high, probably due to extra weight further aft. I do have to trim it lower after raising motor but I expected that. In general I do notice the power trim has much more effect on running angle on this 25" motor/bracket setup than the old 20" motor/transom setup; added a Doelfin which makes that effect even more pronounced which I believe is a good thing. Can plane at 12-13 mph and ride comfortably when it gets rough.

Fr. Frank · #4 06-12-2007, 08:05 AM

Ideally, with brackets you should have your engines trimed pretty far down so as to produce thrust directly along your direction of travel. If you have to trim the engines up to produce best performance, you lose some directional thrust. Thrust angle directly forward, no porpoising = GOOD!

peterb · #5 06-12-2007, 11:55 AM

Chuck,

I am not wild about it either.

Here is what I am planning on doing:
1. When i go down to my boat next I am going to make sure that there is no water in the bracket. Obviously if there is I am going to remove it.
2. As a temporary measure I am thinking of putting a couple bags of sand (150 to 200 pounds) in the bow storage area. Does anyone see an issue with this?
3. I need to get the engines raised. I just have to find someone who has the time to do it.

Also, I have reached out to the previous owner. I did take the boat on a sea trial with him and the surveyor. Between the three of us that was close to 700 pounds (the surveyor was a really big guy). The boat handled fine and it was sloppy out there.

Peter

Capt Chuck · #6 06-12-2007, 10:14 AM

Quote:

The boat is subject to a bronco like ride unless I put the trim tabs all the way down.

Peter

I don''t like this statement. This condition sounds "DANGEROUS" especially when you turn the boat downsea

I would like to see you compensate the porposing by some other means. Maybe moving more weight(gear, batteries, add a fresh water tank etc) up forward

Anyone else share this scenario and what can Peter due solve his problem?