"Forgive the long-winded reply
"Forgive the long-winded reply.
When I researched this question 3 years ago I found that it is highly dependent on the size engine, usage environment, and most importantly, maintenance. I bought my Honda 225 with the expectation of getting 3000 hours. I follow the maintenance schedule as published, with some exceptions - see below.
At 250 hours my dealer found metal filings in the block. It was a manufacturing problem. Honda replaced the block and oil pump under warranty. Since then, everything is working fine.
My usage rate is around 250 hours per year in salt water, with a lot of 30 minute to 1 hour runs at WOT to get to the fishing grounds, then lots of trolling from 700 rpm to 2100 rpm.
One mistake I made when I first got the engine. After the break-in period, I still took it easy on the engine, mostly keeping it around 5000 rpm on those long runs. When they tore down the engine to replace the block, the mechanic pointed out that the engine had not been broken in well. HDS revealed I had less than 2 hours at WOT. After break in, you should run the engine at WOT as much as possible over the next 100 hours in order to fully seat the rings and valves.
Other lessons learned - applies to bigger engines.
1. Replace (or at least remove and inspect) plugs at 200 hours, not the 400 recommended by Honda. After 400 hours, plugs have a tendency to get stuck in the head and cannot be easily removed.
2. When you change oil, always replace the filter, unlike the 200 hour oil filter change Honda recommends.
3. Change water pump impeller every 200 hours, especially if operating in saltwater or shallow water conditions.
4. Install a Racor filter & fuel/water separator in the gas line before the pump up bulb - that does a lot to keep your onboard fuel/water separator and fuel filters clean and trouble free.
5. Use an additive to your gas to prevent phase separation of the ethanol laced gas.
The one thing that is responsible for many outboard engine failures is lack of use. When engines are allowed to set up unused for long periods without proper preparation, a surprising number of things can go wrong."