Aft Engine Installation and Maintenance
Boats with engines located aft offer several benefits over mid hull mounted arrangements but
also require attention to different maintenance items, one of them often overlooked that can
cause serious engine damage.
Most newer boats with aft engines are what we commonly refer to as “pod” drive but this
applies equally to out drive arrangements and boats with Vee drives. Moving the engines aft
provided several benefits:
1. The primary source of noise was moved out from under accommodation spaces and could
more easily be isolated and better insulated making the boat quieter.
2. With pod and out drives a better shaft angle was obtained improving efficiency and /or
upper end speed range.
3. Greater flexibility in interior arrangements and more storage.
4. Incorporated the use of joy stick control making maneuvering the boat easier.
5. More simple installation
While most of us are aware of the added maintenance pods and out drives require too many
owners do not think about the need to maintain the water tight integrity of the machinery.
Typical engine and pod drive installation compartment which is now more exposed to water ingress now that it is under the cockpit vs. being under some sort of cabin space.
High horse power modern Diesel engines require significant volumes of air for proper
combustion. While these spaces are fitted with large air boxes with de-misters the engine
compartments are typically under vacuum when the engines are operating due to the notable
amount of wire the fines pull in coupled with the compartment exhaust blowers. As a result
any failure of the the engine compartment gutters/drains and hatch gasket will result in the
vacuum pulling water into the compartment and thence into the engines! Kept tight, all of the
air gets to engines through the air boxes. If moisture from spray, rain, etc get into the air
boxes it ends up clinging to the de-misters and being drained away.
As brokers/dealers we attend a lot of surveys and have run into multiple situations where
engine hatch gaskets, gutters, and drains have not been maintained there by allowing water to
be pulled into the engine compartment and aspirated by the engines resulting in premature
wear and in some cases catastrophic failure.
So what to do as an owner to avoid that kind of expense?
First once a quarter, while your boat is in service, when you otherwise have your hatch open to
check fluids, spend a minute or two inspecting your hatch gasket and the ridge on the gutters.
Engine hatch with a double compression gasket.
Check to see that your gasket is intact and the that there are no areas where the glue has failed
or anything else has happened to distort it or cause it to drift out of place. Also look at the
interior ridge of your gutter making certain that nothing has damaged the finish on that ridge.
Even a minor gel coat “ding” or chip could allow water to be pulled through.
Second: Every time you wash your boat down or open the engine compartment hatch inspect
the gutters themselves for absolute cleanliness. Any dirt or debris, especially if it gets upon the
gutter ridge is soon to cause problems.
Above we have a reasonably clean gutter and drain
Troubles below! See the debris clogging the drain? As soon as some water gets to the cockpit
deck it will lay in the gutter until filled and ultimately find its way to the air intake on the engine.
A few other thoughts. Gaskets don’t last forever, an an annual basis run along the gasket with
your finger tips making sure it is still pliable and replace it as soon as there is any indication the
gasket is hardening. Most builders install a “compression” gasket which literally compresses
as you secure your engine hatch, there should be easily detected pliability.
If you are a seasonal boater one way to extend the life of these baskets (or any other in your
boat including ports and hatch gaskets) is to allow them to “relax”. If your boat is stored inside
or carefully covered where rain or snow cannot get into the cockpit, simply cracking the engine
hatch, inserting a couple of soft wood blocks, perhaps with a bit of carpet on them, at the
corners opposite the hinges and then resting the hatch on them will allow the gaskets to
regain their original condition.
Aft engine installations have provided us, as boaters, innumerable benefits but they come with
Engine rebuilds are incredibly expensive and I have witnessed the angst an owner has gone
through when he realizes the need for it was due to oversight of these simple maintenance
steps. As is so often the case if you take care of the equipment it will take care of you, in this
case it is all about cleanliness and easy to do.