Engine access: Sterndrives

Crawling around an engine bay, trying to reach some deeply buried component with three flex fittings on a socket wrench, is nobody's idea of a good time.

Thankfully, at least a handful of production boat builders have recognized this, and offer reasonably good access to the critical bits of the sterndrive system's prime mover.  Still, it seems there will always be a few that insist you hire a double-jointed 8-year-old with the mechanical skills of a Formula One pit crew just to change a spark plug.

At least among the single-engine runabout crowd, Volvo installers seem to give a bit more thought to access than do Merc installers.  It's never fair to generalize, of course, but it does seem that- more often than not- red blocks are easier to reach.  So, without further ado, here are a few features I like, a few I don't, and a few that would have the aforementioned 8-year-old cursing like a longshoreman.

The tall, well-secured nets on either side of this Campion's 4.3L Volvo are worth noting.  Obviously, piling loose gear in the engine bay is never a good idea.  But in a six-metre runabout, at least a few owners will inevitably dump things back there anyway.  So you may as well keep that junk contained, lest it find its way into the serpentine belt.

Volvo 4.3L V6 in Campion engine bay

This installation gives you easy access to most of the important bits- filters, dipsticks, the water pump, the alternator, etc.  It's also not at all difficult to reach the bilge pump (somewhat undersized- more on these in a later post).  The business end of the motor, as usual, is a bit harder to reach, and I'm not a fan of engine mounts lag-bolted directly to their bearers.  But I'd much rather work here than on our next one....

Poor access to a Mercruiser sterndrive through a too-small hatch

That Mercruiser is shoehorned into a space that is just too tight for it.  While the critical fluids are easily reached, anything that breaks on this rig is going to be expensive to reach.  You can barely get your arm halfway down the side of this engine, and any serious work is going to involve either removing a lot of good components to reach the broken one, or pulling this whole section of the deck.  And, in one of those "what were they smoking" moments, someone decided that the small baffles that keep loose gear from flying into the engine should be carpeted.

Not to pick on the black blocks too much, here's one on a Maxum runabout that's a bit easier to reach:

Better access to this Merc in a Maxum runabout

The hatch opening is still a bit tight, but at least you can get to most of the critical bits without scraping your knuckles too badly.  This particular 4.3L V6 is fitted with Mercruiser's TKS starting system, which supposedly eliminates the tedious fiddling with throttle and choke settings that used to plage carbureted engines.  As emission control regulations continue to get stricter, I suspect this line will eventually disappear, for better or worse, in favour of the EFI variant.  And no, I don't know why the extra can of gear oil is stored there.

Key Observations

  • Easy access to all sides of the engine is essential.  And "easy access" means at least two feet of room- enough to get your forearm in and swing a socket wrench.
  • Engine hatches need to be BIG.  Ideally, they should be big enough to replace the whole engine without dismantling the deck.
  • Key components (at a minimum: all filters, pumps and belts, air intake, throttle cables and control harness) should be reachable, without tools, simply by opening the hatch.

In a later post, I'll look at a 19-foot Doral that includes what I'd consider to be one of the neatest, most well-planned engine bays I've seen in a runabout.




Agree completely. In fact, at

Agree completely. In fact, at the moment I'm removing the twin stern drives from my boat. They simply are not seaworthy!

They're not for all boats, but can be right for some

Matthew's picture

I don't think I'd go so far as to say sterndrives in general "simply are not seaworthy", but there are certainly a few installation shops out there that make them so. A fairly common installation is to cram the engine into a tight-fitting bay with a small hatch, and omit the watertight bulkhead ahead of it. Such a setup discourages regular maintenance of hoses, fittings, etc. and could easily sink the boat as a result.

I often recommend sterndrives for freshwater and trailer-dwelling planing boats where more than about 150-200 hp is called for; they have a pretty good track record in these conditions and, if well maintained, can easily live 20 years or more. For anything that stays in saltwater for extended periods, my vote goes to other options- jets, surface drives, outboards or conventional shafts- that are more easily protected from the damage that saltwater can cause.

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