"Mid Size Power Boats": A Guide for Discreminating Buyers - by David Pascoe


BERTRAM 46 Convertible

In recent months I couldn't understand why we were getting so many e-mails asking about this boat. I had thought we had a review posted up here, and I know  that I wrote one. Well, looks like the dang computer ate it. My prediction about very large hard drives is coming true; you get so much stuff on them that you can't finding anything and it got lost. Well, maybe its for the best because in the last couple months we've done two more 46 convertibles and one 46 motor yacht, and what I had previously written about the speed of this boat was not quite right.

Bertram 46 ConvertibleBertram 46 Convertible

The hallmark of good design: Twenty years later it still looks good. No passe trend of the minute here.

Since speed is the number one question asked,  here's what we got out of the latest sea trails of a 1979 and  '82 Convertible with the aging 8V71TI's, (the '79 boat engines were reportedly rebuilt in 1996), and  rated at 435 hp, back in the days when Detroit Diesel used pretty conservative power ratings. The '79 boat had mismatched propellers, one being cupped, the other not, one was bent, the other not, and we pulled a consistent 23.6 knots upwind into a good 18 knot breeze. Engine RPM's were 2150 and 2275 WOT. It will stay on step at 16.5 knots at 1800 RPM. This boat had no tower, only a Bimini top with enclosures, no chair and was lightly loaded with less than half fuel and water. Keep in mind the engines on this boat were not turning up to full rated RPM of 2350.  Neither were souped up with oversize injectors.

The '81 had a half tower, chair and more equipment, and the speeds were roughly 1 knot less across the board under similar conditions.  Most likely, my memory of the 46C being an 18-20 knotter was based on full tower boats with all that extra drag. We didn't have much wind in the tower to slow it down that much, but rest assured that it does.  In any case, that's not too far off, and I found in the tattered old Bertram manual the speed and fuel table as supplied by Bertram for the"Bertram Yacht" which I take to mean the MY and not the convertible. Bear in mind that the MY is a heavier boat.  It is reproduced below.

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Click for larger image.

You can whack a good two knots off those numbers for any boat with a tower. You'll note that there is a disproportionate leap in speed between 1800 and 2375 RPM. This is very typical of the deep vee hull that is much less efficient at lower speeds. This is also the reason why people tend to run the engines faster, since the most efficient speed is very close to top speed. This, in my view, makes the boat underpowered. You want to run them no more than 2100, at which point you're barely doing 20 knots. For maximum life, 2000 RPM is better. (The faster a deep vee goes, the more the hull rises out of the water, resulting in less drag and the big jump in speed toward the top end.)

We've been asked many times what would be a good repower choice, and have replied that the 6V92 at 500 hp would be a good choice. It is virtually the same cubic inch displacement, but is a considerably stronger engine that will cruise this boat comfortably at 22 kn. at 2000 RPM.  This more compact engine also frees up a lot of engine room space, making maintenance easier. I don't favor any of the inline 6's because the power comes too high on the torque curve. The vee engine handles the high speed loads much better. However, all bets are off for 6V92 engine souped up to 535 or 550 hp; I guarantee you they will not last.

Bertram 46 Convertible  -  Deep Vee  Hull

A true deep vee hull, one look from this aspect and you know why this is a superior rough water boat.

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Proof of the theory: knocking down a 3' tide rip in the Gulfstream outside Port Everglades inlet at WOT, leaving the wake far behind.

Heading out Port Everglades we had a nice 3 foot sea (I don't overestimate wave height. Most folks would call these four footers) from the southeast meeting an outgoing tide putting the waves into straight up and down mode. As you would expect, the Berty just chopped right through them, albeit with plumes of spray cascading over us; this is a very wet boat. Both in the tide rip of the inlet and beyond into rolling three footers stretched out by trade winds blowing with the Stream, there was no pounding or suddering. Right away you know you are on a very heavy boat by the nice, easy motion. In meeting a wave, the bow does not rise too quickly to throw you off your feet, which is where all that spray comes from. That deep vee parts the waters like Moses crossing the Red Sea. In a beam sea, she rolls more than a shallower vee with large chine flats, at which point you gotta do some serious hanging-on. But she meets her strength again in a following sea at speed, where the fairly full bow reveals no tendency to submarine, and little tendency toward broaching, but you do have to work to keep her on course. The autopilot is useless on this point and will only work itself to death.

Heading into a quartering sea with the full bow is the real weakness,   as she pitches and yaws severely, at which point you need to do some tacking to get where you want to go. Then, again, only a much finer entry bow such as a Buddy Davis or a newer Viking SF can handle this point of attack very well. A Hatteras will do a bit better because of its finer entry, but not all that much. Once we got out of the tide rip, we could carry full speed into the stretched-out three footers, but it was not a pleasant ride, nor would it be in any boat. When you hear guys talk about going full bore into four footers comfortably, time to get out the salt shaker; they stretch the truth a bit.

Bertram 46 - Bow

Although the deep vee maintains the same deadrise angle throughout the length, the fullness of the bow and a very narrow chine flat makes her a wet boat.

The motor yacht we recently surveyed, a 1976 model, was a north eastern boat that was beautifully maintained. Believe it or not, the original gel coat was polished and still had a beautiful shine on; its no secret that Bertram used a top quality gel coat from Cook Chemical which proves that with some care, the finish can last indefinitely if the builder will use a quality material. I was so surprised that I had to do a double take to make sure that it hadn't been painted. The two 46C's were dull, but the finish wasn't chalky or porous and would could be restored with a good compounding. The 46C and the 46 My are the same identical hulls with just about everything the same except the addition of the aft cabin. But the MY is heavier, squats more because of more weight aft, and weights about a ton more, and therefore is slower.

Basically, these boats are everything we've said they are in other reviews. They are well engineered, and at 1000 lbs/ft. they are heavy boats, but they do not have the tremendously thick laminates that many people think they do. One guy told us his 31 is 1-1/2" thick on the bottom! I can assure you that Lee Dana, the chief designer at Bertram, was not interested in building tanks. I have seen three wrecked 46's lately, everything from hurricane damage to having their bottoms torn out on reefs. The hull average only about a 1/4" -3/16" on the sides and 1/2 to 5/8" inch on the bottom, which is not heavy by anyone's standard. What makes them different is that Bertrams are properly framed, unlike so many others where the objective seems to be to use as little framing as possible. Most of the weight in this boat comes from the tons of plywood used on the interiors.

In keeping with that, we found serious stress cracks around the port strut base, which has a 1.5" x 8" wood doublers laminated into the bottom. Over the years, water has probably gotten at the wood and we suspect that the wood has deteriorated. There was quite a bit of vibration and flexing of the bottom panels running at speed, suggesting that the doubler has been seriously weakened. This is just one of the many things you have to deal with when buying an old boat. This may have been the result of prior damage, but in any case, a major repair was needed.

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Something you may not expect to see on a Bertram, but there it is: stress cracks around the strut. This is probably the result of a molded-in wood doubler that got water in it and deteriorated, causing the bottom to weaken. Cracks were found on the interior also. Not the armored tanks that many people think they are. This condition may be the result of prior damage.

The '79 model had the fiberglass cockpit deck which was in fine shape, but the mica on plywood tackle centers and side liners which were badly rotted. There is no core in the hull at all, but the decks have both balsa coring and plywood around the winch and cleat bases. Someone had drilled lots of holes in the bridge deck and water had gotten in and raised up some really big blisters in places. And speaking of blisters, the bottom was loaded with big ones, running anywhere from 1" to 4".  It was no secret that Bertram tank coated their hulls, the technique of using a high quality resin on the outside, and lower quality stuff everywhere else. Sometimes the layup crews make mistakes and use the wrong stuff in the wrong place, which is probably what happened here. Or maybe it was laid up on Monday after a holiday week end. Who knows? Asking why a boat has blisters is like solving the riddle of the Sphinx.

Another weakness is the awful stainless over aluminum rub rail that was a corroded mess.  The problem here is that most of the bolts on the back side can't be reached without tearing the boat apart; otherwise one could just replace the rails. This problem  really hurts this boat because the rail becomes so ugly and there is basically nothing you can do about it. At least at reasonable cost. One of our boats had spent most of its life in the islands, where there is little fresh water and they don't get washed down often, which partly explains why the aluminum rails looked so bad on this one. Yet many others don't look so good either. The overall exterior looked fairly good, but the maintenance below decks was terrible. 

The engine room vents are poorly designed and they pull a ton of salt spray into the engine room, a factor which I attribute to why the 8V71's in this boat have a  faired poor track record. One look in the E.R. and the effects of the salt spray are immediately obvious. The aft bulkhead is nearly water tight, so the engines are only pulling air in through the side vents. One option to solve the problem would be to redirect the air intakes from under the cockpit and close off the side vents.  Or you could build dorades into the hull sides and add fiberglass filters. Another is to add Walker AirSeps, but that won't solve the engine room corrosion problem. In any case, unless you do something, your engines are going to be sucking salt.

In recent weeks we've polled three full-time engine surveyors on the subject of the service life of the 8V71TI engine. Frankly, I was surprised to get three quite different opinions: great, ho-hum and terrible. 

Only one of the three mentioned the fact that when you attempt to pull too much power out of them, you are greatly reducing service life. Actually, this is a well-proven engine, and 435 is not too much power to squeeze from this block, but it is close to the edge, and  it does have some notable problems with the turbo/intercooling system. In addition, failure to maintain the airbox drain/respiration system can shorten engine life drastically. With good maintenance they perform reasonably well as long as you don't push them too hard. Good maintenance service life generally runs 2000 - 2500 hours depending on how many years those hours were accumulated.

Sucking up salt spray  is one reason why engine hour meters often don't mean anything. The Allison M20 gear boxes to which they are usually mated, originally designed for 165 hp, are known for bearing failures.

There were only light stress cracks that were not very obvious appearing on the toe rails in a few spots. The windows and frames were in good condition although there were a few corrosion holes in the slide channels from years worth of accumulated salt. The frames are painted so they can easily be pulled and the holes welded, and then repainted. And since the hull is glassed to the deck, there were little or no interior leaks and thus no water damage. Even the custom made (not residential grade), aluminum framed sliding salon doors still worked well.

The electrical systems were in surprisingly good shape and hadn't been all buggered up with jury-rig alterations and repairs. This model has a separate 32 volt battery compartment under the cockpit deck that is very easy to get to.  But it also has the generator under the cockpit deck as well. The hatch cover is very large, affording good maintenance access, but the hatch gutters are very shallow so that if you blast the deck with a hose, you know where some of that water will be going. This one had a two year old Onan 12.5 kw unit in the 4 door sound shield. Apparently Onan has now  abandoned those god-awful 3600 RPM Japanese diesel they were using for a while. This was a 1800 RPM engine that was very quite, but you can't say the same for the 3600 RPM jobs that scream like a banshee. The trademark Onan crapola soleniod switches are still there and, of course, they crapped out. We had to wire them open to make the engine run.

The Bertram 46C was built for 18 years and there are a lot of them around, worldwide. Because they are Bertrams, most have been used like Bertrams, meaning they've had a hard life. Some of them are pretty clapped out, but there are a lot of major refits floating around too. These boats make exceptionally good refit projects because they have a timeless styling that maintains their good looks and desirability. One of our survey models was selling well under $150k but I wouldn't necessarily say that it was a real bargain.

What you will find on many of these boats are the exhaust systems, plumbing, appliances, pumps and motors, and sometimes the electrical systems, have been jury-rigged and bastardized to the point of no return because of folks who don't want to pay the cost of doing things right. Thus the burden of correcting all these problems is going to fall on you.

Don't  make the mistake of thinking you can pick one of these boats up for around $150-175k and have a nice boat that's ready to go.  Most of them need a cash infusion of at least $50k or more to rectify decades worth of deferred maintenance. If you have to do engines and generators, its going to be a lot more. If you expect to find one with all the machinery in top shape, you are dreaming. Really.  The engines are usually the last thing anyone spends money on. Then figure that most of the systems will need replacement, not merely repair.  One of our survey boats could gobble up $100k in a heart beat, and the other one already had.

Remember that you're looking at a boat with a Replacement Cost of over $700k and there's no way you're going to get off that cheap. Don't put yourself in the hole by wishful thinking. Part of what you save over the cost of a newer boat has to be put back into an older one.  Otherwise, all you'll end up with is a clapped out old boat that is going to bleed you bankrupt anyway. And when you try to unload it to release the burden, you'll be facing a fire sale. This is one of the reasons why older boats end up going down hill fast. People make the mistake of thinking the purchase price is the cost of ownership. If you want to be conservative about it and not shoot youself in the foot, add at least 50% onto the purchase price as the cost of getting it back in shape. Even so, you're still looking at less than half the cost of a new one.

I give the 46C a four-star rating, which is one less than I gave the 45-46 Hatteras Convertible. All that wood in the cockpit, a less than great interior and the shoe-box engine room are significant negatives. Yes, it outperforms the Hatteras in rough water, and it is certainly a better looking boat, but the difficulty in maintaining this boat has to be a consideration for the budget minded.

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David Pascoe - Biography

David Pascoe is a second generation marine surveyor in his family who began his surveying career at age 16 as an apprentice in 1965 as the era of wooden boats was drawing to a close.

Certified by the National Association of Marine Surveyors in 1972, he has conducted over 5,000 pre purchase surveys in addition to having conducted hundreds of boating accident investigations, including fires, sinkings, hull failures and machinery failure analysis.

Over forty years of knowledge and experience are brought to bear in following books. David Pascoe is the author of:

In addition to readers in the United States, boaters and boat industry professionals worldwide from over 70 countries have purchased David Pascoe's books, since introduction of his first book in 2001.

In 2012, David Pascoe has retired from marine surveying business at age 65.

Biography - Long version

Articles at
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David Pascoe's
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Mid Size Power Boats Mid Size Power Boats
A Guide for Discriminating Buyers
Focuses exclusively cruiser class generally 30-55 feet
With discussions on the pros and cons of each type: Expresses, trawlers, motor yachts, multi purpose types, sportfishermen and sedan cruisers.
Buyers' Guide to Outboard Boats
Selecting and Evaluating New and Used Boats
Dedicated for offshore outboard boats
A hard and realistic look at the marine market place and delves into issues of boat quality and durability that most other marine writers are unwilling to touch.
Surveying Fiberglass Powewr Boats
Surveying Fiberglass Power Boats
2nd Edition
The Art of Pre-Purchase Survey The very first of its kind, this book provides the essentials that every novice needs to know, as well as a wealth of esoteric details.
Marine Investigations
Pleasure crafts investigations to court testimony The first and only book of its kind on the subject of investigating pleasure craft casualties and other issues.
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Links to Each Chapter Contents with Excerpt at:
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Last reviewed August 07, 2015.