Caterpillar 3208 marine diesel: what to check before you buy the boat

The Caterpillar 3208 V8 diesel powered a great many motor yachts, convertibles and larger cruisers through the 1980s and '90s, in both naturally aspirated and turbocharged versions at a range of horsepower ratings. It's a heavy, robust engine with a long track record and wide mechanic familiarity.

A 3208 can be a great engine or a tired one, and the difference is almost always the rating and how the last owner drove. A fast boat with hard-run 3208s and no records deserves an engine survey before anything else.

Cat 3208 at a glance

Is a 3208-powered boat right for you?

A good fit if the engines are a moderately rated version used gently, records show regular service and a clean oil analysis, and a Cat-experienced mechanic is nearby.

Think twice if the engines are a high-output version that's been run hard, the boat is a fast sportfish with high hours and no records, or you can't find a mechanic who knows them.

Why the rating matters most

The higher-output turbocharged versions work much harder than the naturally aspirated ones. Marine engine makers rate engines for duty: Volvo Penta's scheme, for example, runs from continuous duty for working boats down to pleasure duty, under 300 hours a year with full power at most one hour in twelve.¹ The same number of hours uses up far more of a hard-working high-output engine's life. Find the exact rating of the engines you're looking at, and ask how the boat was used.

What to check

• Cooling system: heat exchangers, aftercoolers on turbo versions, raw-water pumps. Ask for service records and look for coolant crust and corrosion.
• Smoke: a clean cold start, and no persistent blue, black or white smoke at cruise or under load.
• Blow-by from the crankcase breather.
• Oil analysis for wear metals, fuel and coolant on each engine. One popular lab has charged around $35 a sample.²
• Hours and rebuild history: when, by whom, what was done.
• Engine room access: V8s in twin installations can be very tight. Look at the outboard sides of both engines, which are often the most neglected.

On the sea trial

Each engine should reach its rated wide-open rpm briefly with a normal load. Run each engine alone as well as together: one engine falling short points to a problem with that engine. Watch the temperatures and the smoke at full load. See the sea trial checklist.

Questions to ask the seller

• What's the exact model and rating of the engines?
• How fast do you usually cruise, and at what rpm?
• When were the engines last rebuilt or overhauled?
• When were the heat exchangers and aftercoolers last serviced?
• Who's your mechanic, and can I call them?

Get an engine survey

Twin diesels are often the most valuable part of a boat like this, and the biggest risk. Have an engine surveyor who knows Caterpillar aboard for the sea trial, with oil samples from both engines. See boat survey cost.

Common questions

Is the Cat 3208 a good engine?

It has a long track record and wide mechanic familiarity, and lower-rated versions used at moderate loads have a reputation for long lives. High-output versions run hard are a different story.

How many hours is a lot for a Cat 3208?

It depends on the rating and how it was run. A moderately rated engine used gently can run far longer than a high-output engine pushed hard. Records and an oil analysis tell you more than the hour meter.

Should I buy a boat with high-hour 3208s?

Only after an engine survey, oil analysis and a sea trial show healthy engines, and with the price reflecting a possible overhaul.