Outboard vs Diesel for Horizon Cats

Compac Horizoncat

While many people prefer the inboard diesel engine for the Com-Pac Horizon Cat, I prefer the outboard.

Nine out of ten Com-Pac Horizon Cats sold are the inboard diesel Horizon Cat version, and one out of ten is a Horizon Cat with an outboard engine. Make that tenth one for me!

In no particular order, the advantages of an outboard over a diesel engine:

  • The outboard is quiet.
    Wind noise will drown out an idling Honda, but that one cylinder diesel at idle sounds like the African Queen. When cruising under power, the cabin is a much more serene place without a diesel engine.
  • The cabin is a cooler place without the heat from that engine.
    Insulation can only do so much to mask the fact that there is a diesel engine running right beside you. Outboard power means better napping.
  • Diesels take up a lot of space.
    The space that would otherwise be filled by the diesel can serve as a nice, large storage area in the outboard version of the boat.
  • The outboard can be independently steered
    It makes it easy to put the rudder one way while approaching a dock at an angle, and put the outboard the other way and in reverse, resulting in a power sliding stop alongside the dock.
  • The outboard can be an emergency steering alternative
    In the event of a broken steering cable or connection, the outboard provides a way to steer the boat, at least under power. Thanks, Rahn, for reminding me of this benefit of your boat.
  • An outboard can be tilted clear of the water
    This allows you to eliminate the drag of the propeller, and the potential for entangling something on the prop. Why drag a prop around when sailing?

    If I wrap something around the prop of an outboard, I might free it without getting wet. I'm a real sissy when it comes to water below 80 degrees, and I don't like to swim in the ocean at night. Similarly, if an outboard's water intake grabs a plastic bag, you can reverse or tilt the engine to free it. If a diesel's water intake grabs a bag, it can mean a swim in conditions where that is not fun, and may be dangerous.

  • Holes in hulls ultimately cause trouble, particularly below or near the waterline.
    The diesel needs a water intake hole, a shaft log/stuffing box, and an exhaust. The only hole needed for the outboard version is above the waterline, for the fuel line. I would put an additional above-waterline hole for remote controls.
  • I hate bleeding diesels and changing the oil
    I make a mess and leave a diesel smell that is hard to eliminate. I don't care much for working on engines or transmissions in tiny spaces, either. An outboard gets worked on in a shop, next to a full tool set, under a fan, while standing or sitting comfortably.
  • Outboards are easier to clean
    An outboard engine is easier to flush with fresh water after using it in salt water than a diesel.
  • Outboards are less expensive
    For the price of the diesel option, I can buy two really nice remote-controlled, electric-start, power-tilt outboard engines, and still have money left over. If one breaks, I go boating anyway with the other, and fix it later.

The downsides for an outboard

There are legitimate arguments in favor of the diesel, and in the interest of fairness I'll present those here:

  • While an outboard with a 20" shaft will work fine most of the time, you really need a 25" shaft to keep the engine from cavitating when powering into a chop. Even with the XL shaft, I would think that it can cavitate if conditions get bad enough, which is when you need it most. It would be really hard to get that diesel's prop out of the water.
  • The remote controls are nicer on a diesel, and the diesel can handle a larger alternator. The diesel is also more efficient, but fuel burn on little four stroke outboards is minimal anyway. Most sailors have more trouble keeping fresh fuel than running out of fuel.
  • Resale value on the outboard version is going to be terrible. No one wants the outboard version (except me).
  • An outboard, especially an XL shaft when tilted, sticks way back off the transom. You can hit things with it in tight areas.
  • The weight of the outboard engine is hanging off the back on the port side. You can balance the outboard's weight with stuff like tools, anchors, etc that are heavy, but you might not want to store those things forward and on the starboard side. The diesel's weight is down in the bottom of the center of the boat.
  • This, I think, is the big one for most people: The boat looks better and seems more like a little yacht without that silly outboard hanging off the stern.


  1. I have this version as well, and am satisfied with the outboard. I test-sailed the diesel version when I was looking at the boat, and it was pretty neat. However,I realized that in north Texas, there are very few marine diesel specialists, but lots of good outboard mechanics, and this influenced my choice. That, and the price difference. Really, the only problem I’ve had is moving the motor up and down on the motor mount, as my motor lock gets in the way. As far as balance goes, the battery box is on the stbd side, and balances out the motor on the port side. BTW, if you want a cheap motor mount, try the one on a Catalina 22; Com-Pac has a much better one.

  2. I have one of those ‘cheap’ motor mounts. They are purchased by Hutchins from West Marine or other outlets. My 5 hp sits on mine. It is rated for 20 hp. More then you’ll ever need on a H.C.


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