CONTINUOUSWAVE

Hi all, I currently have [a 1987--please always use four digits to indicate a year] Revenge 20 Walk-Through with a [1998] Mercury Offshore 200 main engine and an 8-HP auxiliary engine using four-stroke-power-cycle design. The combined weight of these two engine is about 480-lbs.

I may get an an older four-stroke-power-cycle engine to replace the main engine; the engine I may get will weigh 583-lbs. Then the combined weight on the transom with the main and auxiliary engines may be 670-lbs. Also on the transom is a battery

Q1: Is [a combined weight of a main and auxiliary engine on the transom of a 1987 REVENGE 20 at 670-lbs] too much weight?

I had a REVENGE 20 Walk-Through, also a 1987 model year. I had twin Yamaha 70-HP engines, mounted on 10-inch set-back brackets, and two batteries in the splashwell. Since the engines were set so far back, I also had a cooler in the mostly empty engine splash well. There was also hydraulic steering gear and a tie-bar with gimbals between the engines.

I do not have exact figures, but I estimate the weights were:

• (2) Yamaha 70 260-lbs = 520-lbs
• (2) 10-inch brackets 40-lbs = 80-lbs
• (2) batteries 50-lbs = 100-lbs
• cooler 30-lbs
• hydraulic steering gear 25-lbs
• TOTAL = 755-lbs

There was no particular problem with the transom weight. The boat did not have any particularly bad static trim. When the boat was in operation I generally kept the engine splash well drains plugged so that no sea water would enter via those drains and fill the bottom of the engine splash well. I wanted to keep the splash well completely dry because I had the cooler in there, and I did not want it to float around on any water. Also, on long cruises I had an additional on-deck fuel tank in the aft end of the cockpit, usually with 15-gallons of fuel--another 100-lbs of weight.

Also I installed a small RULE centrifugal water pump in the splash well that lifted any water out and over the transom. During routine operation of the boat, water never came into the splash well. There was one time I recall that I had to go into reverse and back into some oncoming waves--this was several hundred miles north of Vancouver on the inside passage and in a narrow passage with high current. Backing against those wave did produce some water slopping over the transom into the splash well, but the pump cleared the water very effectively.

The REVENGE models have added weight forward due to the cabin superstructure, and the cabin interior tends to fill with gear and adds more weight. So a REVENGE usually floats on a very even trim, not down-by-the-stern as an OUTRAGE tends to float. As a result, having some added transom weight is unlikely to put the boat's static trim into an excessively down-by-the-stern situation.

With my twin engine and set-back bracket set up, the boat floated so evenly in its static trim that I could remove the plug from the cockpit sump on the starboard stern quarter. With the sump open to the sea, the water only rose in the sump for a level of an inch or two, then stopped. You could effectively leave the sump drain to the sea open, and very little water would be in the sump. That is how well the hull tolerated the transom weight.

In my comparison above with my old boat, there was about 625-lbs of engine and rigging hanging 10-inches off the transom, further accentuating the weight by the position far aft of the transom. Compared to your situation with 670-lbs at the transom, I would estimate the two are comparable. On that basis, I don't think you will have a problem if you decide to buy an older four-stroke-power-cycle engine.

ASIDE:

Q2: what older four-stroke-power-cycle engine are you thinking of buying?

Q3: will the older four-stroke-power-cycle engine you are thinking of buying have been used in saltwater?

Q4: how many hours of run-time will the older four-stroke-power-cycle engine you are thinking of buying have?

I have a 1988 Revenge 20 W-T. I contacted Boston Whaler for advice on transom weight. They told me the transom would support about 610-lbs in total weight as the REVENGE 20 W-T was designed to hold two engines. My boat has a 1991 Mercury 200-HP two-stroke-power-cycle engine and a 2006 Mercury 15-HP auxiliary engine.

After doing some research into the subject early 2000s Yamaha 200, known engine exhaust corrosion is driving me away from the potential purchase.

However I’m now wondering how to reconcile the two responses to my question in this thread- if Whaler says 610-lbs total weight is the target, I suppose I should avoid total engine weight exceeding that.

floater wrote:I have a 1988 Revenge 20 W-T. I contacted Boston Whaler for advice on transom weight. They told me the transom would support about 610-lbs in total weight as the REVENGE 20 W-T was designed to hold two engines. My boat has a 1991 Mercury 200-HP two-stroke-power-cycle engine and a 2006 Mercury 15-HP auxiliary engine.

A Yamaha F200 with the 130-lbs auxiliary engine would put around 620-lbs on the transom.

If somebody states that they were running with 750lbs and it was just fine....and this person runs, for a few decades, his own Boston Whaler website. Why would you deny his statements and take the word of "somebody" at Boston Whaler told another person that 610 was max?

Boston Whaler did not ever have weight limits back then and there is probably a good reason for it: it usually does not matter. If I had a dollar for every person who states that a modern four-stroke is too much weight for this or that I would be a millionaire. The problem is every one of those "experts" never owned a classic with a modern four-stroke to even qualify to answer the question.

Sorry for the rant, but the "weight" thing is not a rule of thumb on classics that are built in a different manner than the newer Whalers.

The "quote" is that the transom would support "about 620-lbs." That does not mean the transom won't support 621-lbs.

The "quote" does not state there is a hard limit on the transom weight of 620-lbs, nor is it clear if that weight figure is for just the weight of the engine(s) alone . There generally would have been at least 125-lbs of additional weight in the stern of a classic c.1987 Boston Whaler REVENGE 20 W-T boat with twin engines from two batteries, two engine oil tanks, hydraulic steering and tie bar, and engine control cables.

The maximum horsepower rating for a c.1987 REVENGE 20 is 200-HP. If powered by c.1987 OMC twin V4 engines (about 301-lbs dry weight), the engines would weight at least 602-lbs themselves. What is to be done about the weight of two batteries, two oil tanks, a tie bar, and the hydraulic steering gear? Is that considered in the 620-lbs?

There are two indicators of excessive hull weight loading in the stern that are easy to assess:

• Are the engine splash well drains under water?
• If the cockpit sump drain is opened to the sea, how high does the water rise?

If the engine splash well drains are always submerged and the engine splash well is continually filled with water coming in via the drains, then the boat trim is down-by-the-stern compared to where the designer anticipated.

If the cockpit is flooded with several inches of water when the cockpit sump drain is open to the sea, the boat trim is down by the stern compared to where the designer anticipated.

My Revenge is an older boat than most would have nowadays. I asked the pros at Boston Whaler and 610-lbs is what they told me to keep the weight at. I'm not really sure what the weight is in total on my boat with the two batteries, two down riggers, two 16-lbs weights, the hydraulic steering, the oil tank, and the two engines. But my splash well drains are always under water and the splash well is always half full of water. I have never had any concern with this and just leave it like that.

floater wrote:610-lbs is what they told me to keep the weight at.

Are you suggesting that Boston Whaler told you weight must be added to reach 610-lbs if the engine weighs less? That seems very strange.

This is the info I got from Chuck.

Boston Whaler did not assign a maximum engine weight at this time (no heavy four strokes around back then). This boat was designed around the capability of installing either a single engine or dual two strokes, though.
Most of the 90 or 100 hp engines would have been approx. 305lbs each. For best balance, I'd say about 610lbs maximum for an engine combination.

Regards,
Chuck Bennett
Boston Whaler, Inc.

Now we finally have an accurate reporting of what Boston Whaler customer service in c.2018 (i.e. before Chuck retired) had to say about the maximum transom weight specification for a 1987 REVENGE 20 W-T:

--Chuck said there is no maximum engine weight rating on a 1987 REVENGE 20 W-T

--Chuck felt that "for best balance...610-lbs maximum for an engine combination."

I don't see how this gets interpreted to mean that something awful happens when you get to 611-lbs.

It is also clear that the 610-lbs is for the ENGINE WEIGHT only, and no other weights are to be considered in reach the 610-lbs figure.

Let's get back to the original question:

Q1: Is [a combined weight of a main and auxiliary engine on the transom of a 1987 REVENGE 20 at 670-lbs] too much weight?

A total engine weight of 670-lbs does not exceed any specification limit for engine weight. It will be 60-lbs more than a figure for total engine weight that Chuck Bennett suggested would result in "best balance."

Again, [the 610-lbs] is JUST engine weight and I believe the 305-lbs [referenced for older outboard engines] was without PTnT, propeller, steering, VRO tank, and batteries.

My conclusion: since there is no specified limit on maximum engine weight or maximum engine weight plus normal engine rigging equipment such as oil, propeller, batteries, steering, cables, harnesses, and so on, the engine that may be purchased and may be installed on the transom may cause the "balance" as defined by Chuck Bennet to not be the best. Or, maybe not.

Good summary Jim. The other thing is....no matter how heavy, it still will not sink ;)