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  Setback Brackets: Some observations

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Author Topic:   Setback Brackets: Some observations
jimh posted 09-09-2002 10:40 PM ET (US)   Profile for jimh   Send Email to jimh  
As I mentioned previously, I have installed a pair of Springfield Marine 10-inch setback brackets on the transom of my boat (20-Revenge). I have now had several days of operation with the new set up, and I can make these observations about the effect of adding the setback brackets.

Static Trim The bow now sits about 1-2 inches higher than previously in static trim. The stern is now down about the same about. Previously the splash well drain holes were just touching the waterline; now the drain holes are below water. The drain holes are generally plugged now. I still have to install a pump to clear the water that slops into the splash well.

Weight Distribution-Trailer The trailer weight distribution changed, too. I noticed what appeared to be uneven distribution of weight on the tandem axles--the rear bearings were running much warmer than the front bearings. I moved the boat forward about 3-inches on the trailer.

Ride The most interesting result is the ride. It has definitely improved. Most noticeable is the softer landing of the now when coming down. I think much of this is just due to the longer lever arm the engine weight now has over the pitching axis of the boat.

Speed I don't see any fantastic speed gains. The boat does seem to be able to stay on plane at slightly lower speeds than before. The top speed is close to the same. (We don't really like to run these older engines at wide-open-throttle for very long, so we did not get extensive data at top speed.)

Engine Trim Now the engine trim is typically set farther down. The weight shift is providing some bow lift that previously had to be obtained with engine trim. The engines are trimmed more ahead, with less trim out for lift.

One has to be sensitive to the tendency for the engines to settle down in a big hole behind the boat when coming off plane in a hurry. The water can rise quite high, getting a little close to the power heads.

I don't think in my installation that I have enough horsepower and speed to begin to see siginificant enhancements from the setback and shallower running. In fact, I need to experiement more with the engine height. Since I am using conventional propellers, I probably cannot raise the engines as high as could be done if more aggressive propellers were installed.

The two biggest assets so far are the better ride characteristics and the greater space available in the splash well. All the engine cables are out of the splash well, and that area can now be used for a little storage (which is always at a premium on a classic Whaler).

One thing we discovered just recently: the Springfield brackets that I got were made with 0.5-inch material. They are noticeably heavier construction than the original ones purchased by LHG and Backlash, which were 0.375-inch material.

I'll be experimenting with adjusting the engine height in the future, and I will report any findings. Pictures coming soon, too.

David Ratusnik posted 09-10-2002 08:10 AM ET (US)     Profile for David Ratusnik  Send Email to David Ratusnik     
jimh- Next time out try trimming the engines outward as you achieve plane. I'll bet you pick up a few mph's. It takes awhile to get the feel for this but the result should be very little boat in the water. Minimal drag. Maybe a little walk at WOT. David
lhg posted 09-10-2002 04:16 PM ET (US)     Profile for lhg    
I can verify Jim's comments, as I have now driven his boat "before and after". The brackets made a huge difference in how the boat runs. It certainly rides better, more like a 22 rather than a 20, and handles the seas better, and I think it's a little bit quicker also. A setback bracket installation like this is still highly recommended as far as I can tell.

This Revenge also convinces me that more HP is better than less HP. I think any Whaler should have enough HP so that it can run 45MPH top speed. Not that you're going to go this fast, but to keep the engine rpm's down to a "life giving" operational level, and pleasant riding experience for all in the boat. Cruising a boat along at 30 MPH is reasonable for a lot of pleasure boating conditions, but to do this in Jim's boat with the little Yamaha 70's (otherwise really nice engines) requires running them at close to 5000 RPMs. This is just not comfortable boating, either because of concern you're beating up and wearing out the engines, or the continuous high RPM sounds. It's like driving your car on the expressway in second gear. Conversely, I am used to cruising along at these speeds at more like 2600-2800 RPMS, knowing the engines are just loafing along. I prefer the "overdrive" experience of excess HP. I just completed a 900 mile cruise of the British Columbia coast, cruising along for hours at a comfortable 2200-2500 RPMs, up to 26MPH and getting close to 3 mpg. I couldn't imagine doing this with engines running over 4000RPM the whole time.

From what I can tell, and for the same engine technology operating the boat at the same speed, there is little advange in fuel economy to obtained with low HP engines. A 3 cylinder 70 operating at 5000 rpms gives no better mileage than a 6 cylinder 115 operating at 2800 on the same hull.

The higher HP also gives you the opportunity of taking advantage of some of the higher tech propeller designs, which also enhance hull ride, rather than the standard low performance fare of aluminum and elephant ear SS.

In this latest JD Powers satisfaction survey, they mentioned that underpowering a boat is one of the biggest issues regarding lack of satisfaction both for the engine AND boat manufacturers. They say go with the highest HP the hull is rated for. Or in my case, stretch it a little!

mustang7nh posted 09-10-2002 08:17 PM ET (US)     Profile for mustang7nh  Send Email to mustang7nh     
lhg- how do you push the horsepower "a little". I've talked to several marinas and none will put a higher engine horsepower than rated on my boat. I've a 1988 20 Outrage with same year 200hp Johnson. Runs good but I'd like a bit more on the mid and top end.
David Ratusnik posted 09-10-2002 08:32 PM ET (US)     Profile for David Ratusnik  Send Email to David Ratusnik     
Mustang-- 200 is just fine on a 20'OR. I've seen them set up from 150, 175 to 200. More hp may get you in trouble. Plenty of 22'OR's run just fine with that 200 (my friend's 22 flies with that 200). An Armstrong (3') single bracket should get you several more miles per hour at the top end with the 200. Good Luck .03 David

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