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Our boat was 10 years old with 1200 hrs when we bought it. Only difference is our engine is the turbo version (4JHTE). The previous owners kept good records and for the last 2 years they had it they would run the engine up to temperature twice a month without leaving the dock.

When we first got it the smoke was very bad. I pulled the injectors and had them serviced - about $25.00 each I think - at a local diesel service shop. The difference was significant. The engine still smoked but has improved as we have run it under load. It still smokes a little more than other 4JH's I've seen but not too bad. The frequent cold starts and no load running probably glazed the cylinder walls.

22-2300 rpm at full throttle is way too low. It should go up to around 3600 in flat water. What will it do under no load? Fast idle for our engines is 4000 rpm. You could either have a fuel problem (injectors), an improperly set governor, a false reading from the tachometer or the wrong prop. What is your prop? The original specification is an 18"diameter x 12" pitch. Too much prop will give you low rpm's and lots of smoke. Since ours was a turbo the original fixed prop was 13" pitch. I think it was a little too much as running anything above 3300 rpm caused quite a bit of black diesel smoke. The most I could get out of it was about 3500 rpm. Since the I installed a Martec which has adjustable pitch. It can be adjusted in the water so I made several trial and error adjustments so it now seems to load the engine maximum at about 3600. We normally cruise at 2700-2900 which gives us about 7.2-7.4 kts.

One other thing I have hear about on some engines is obstruction in the exhaust at the cooling water injection point. That's the stainless steel fitting on the back of the exhaust header. I took ours apart last spring and it was clean without any buildup whatsoever.

Hope this helps.