Engine Replacements – Re-build or Re-power?

Dear Dr. Motorhead;

I am concerned about my engine, I don’t know how many hours it may have on it. I am using some oil, rpm’s are dropping, and it’s just getting tired and unreliable. It is time to replace or rebuild. This doesn’t upset me, but I just don’t know what to do. New engines have easily available parts, they are reliable, and weigh less. My friend gets lots of horse power with his V8 and turns about 4500 rpm — really pushes his boat along. On the other hand, it is not original. Do I need to worry about reliability issues with a rebuilt engine? Do I need to be concerned with abusing the boat with a new V8? Is there anything I can do to get a little more performance out of my old engine? Oh wise one, do you see flat heads or valve covers in my future?

Signed, Bewildered

Dear Bewildered;

What do you do? I suppose you could throw away the engine and add a set of oar locks. A lot of advantages to this idea, yet that wouldn’t be original either, not to mention speed or the lack of it. If you are asking this old salt what you should do, then I would say keep it original, but let’s discuss the options.
Buying a set of oar locks:
Advantages: a lot less money than a new engine; no maintenance costs; don’t have to buy gasoline; no pollution; quiet operation.
Disadvantages: a lot of work; very slow; not original, gives new meaning to a racing runabout.
Adding oar locks is probably the last choice for you, so I won’t spend much time on this option. However, if you get my point, modifications to originality doesn’t necessarily mean changing to a V8.

What about a V8? You get speed, light weight performance, lots of rpm’s. What you don’t get is the same sound, looks, feel, and high torque performance you obtain with a flathead engine. V8’s get their best torque at a high rpm. Combine a smaller propeller with lots of rpm’s and you get V8 performance. What you really need in a boat is lots of torque; your engine is always under load. Certainly horse power is important, however, torque is the key component. For instance, the big Kermath or Sterling Petrel’s maximum engine speed is around 2000 rpm, developing about 200 hp. Yet they deliver a tremendous amount of torque. You can have one person in the boat or a whole load of people and you will always have the same speed and engine rpm. You can never make this statement about a V8. Another example of torque, is a diesel engine. Tons of torque, with just a little horsepower. A farm tractor can pull a house off it’s foundation, yet it may develop only 80 horsepower. So what am I getting at? You will go faster, but to do so, your propeller is back there spinning at 4600 rpm. This, in my opinion, gives you the feel of riding in a Correct Craft ski boat. You lose the sensation of the feel; you also lose the sensation of the sound. The two engine types just sound different. Is your boat original? Then shouldn’t your engine be original? Just one man’s thought.

About the abusing-your-boat question? Do you know what they call a Chris Craft with a V8? A Century. Ha Ha. Like any boat in motion, the biggest abuse comes from the operator. If you are going 50 mph instead of 35, be careful. Most Century’s leak first because they are constructed lighter, secondly because they get the bejesus knocked out of them. Be careful if you want to go fast, let the water be smooth. Many people who do complete restorations to their boats, install modern bottoms and stiffen up the structure knowing they are going to install big power.

What about rebuilding a flathead? Yes you can, it’s less expensive than a new V8. If you rebuild it, then go all the way. Do what your engine guy says to do. Install new bearings, valve springs – polish, grind, and hone it all. In addition, I strongly recommend that you balance the engine components and flywheel. Some suggest that you install hardened seats. I suggest you save your money. When you rebuild, you don’t have to rework the engine compartment and its components — another plus. Installing a V8 means new plumbing connections, new prop shaft, and throttle linkage, to name a few.

What about reliability in a flathead? They are so simple, so straight-forward, so basic, nothing could be more reliable. These engines were either built for industry (Hercules aka “Chris Craft,”) or directly for the marine market (Chrysler, Kermath, Sterling). They were designed to run under load for long periods of time. Properly maintained, you can put thousands of hours on one of these motors. Parts are easily available for the Hercules and Chryslers, but not the others, so you got me there. If you have a Kermath, talk to Jim Aamodt. If you have a Sterling talk, to Steen Melby. If you have a Scripps, talk to Pete Henkel —. all ACBS members.

Are there some things you can do to tweak your flathead to get your boat going a little faster? Absolutely. But, if I get into this topic now, then I wouldn’t have anything to write about next issue. Be patient.

Do as the good Doctor does, keep it original. Old boating fulfills the senses of sight, sound, smell, and hearing. For me, these senses are compromised with a small-block Chevy sitting between the stringers of a 1939 Barrel Back. But, what the heck, this is America. We have choices and the freedom to chose.

Dr. Motorhead