Exhaust smoking

[graywill]

I have an '02 Supra Santera that is well kept and in good shape. While in a cove this morning, I hit a shallow spot and stirred up some soft mud with the prop. I carefully maneuvered back to deeper water and thought that everything was OK. Once back on open water, I nudged the throttle to cruising speed but found that the motor seemed to bog down and wouldn't accelerate past a certain point. I tried clearing the prop and did not detect any obstruction. I noticed white smoke coming from under the ski platform. At this point, I checked the engine temp and oil pressure gauges and both were at normal levels. I also checked the engine compartment and everything seemed fine - no smoke, loose hoses, errant fluids, etc. Since the boat would cruise at a low speed, I decided to head back to the slip. The ride was 5-10 minutes and smoke was coming from under the ski platform the whole time. Once the boat was dry docked, I checked the underside of the boat for obvious signs of damage or problems:

- water intake valve was clear of obstructions
- prop and shaft were OK and functioned properly
- rudder was fine
- plugs were in

The only noticeable problem was that white smoke kept coming out of the exhaust pipes when the engine was running.
Given the lack of obvious physical damage, I feel like I may have sucked some mud into the engine. However, what would that have to do with bogging down the engine while accelerating out of low speeds and smoke coming out of the exhaust?

Thanks for your help and advice.

[cadunkle]

Does it smell rich? White/light colored smoke is either rich and extra gas (it will be obvious, should smell rich and maybe burn your eyes when you put your face in the smoke) or hot and steam from water. Rich might make sense for bogging down. In that case I got no idea about fuel injection. If it's steam you might have a plugged up coolant line, thermostat or thermostat housing, or manifold/riser. I would start by pulling the drain plugs in the engine adn manifold and see if you get clean water or lots of sediment. The manifolds you might be able to reach in with a finger and work out the sand, the block try using a pick to get whatever you can. You can pull the coolant hoses to the manifolds and flush with a hose to help clear them. Worst case the risers are clogged and you can try pulling the rubber exhaust hose and clearing them, or pull the riser off the manifold and clean the coolant passages and replace with new gasket. Could also pull the thermostat housing and clean that up. Basically you're just pulling as much of the coolant system apart as is easily accessible and cleaning out whatever blockages and sediment you find. That would not explain the bogging though.

The marina I use is very shallow at low tide and I'll sometimes stir up mud while getting in/out or on/off the trailer. Never had any trouble and just flush out the small amount of sediment I find at the end of the season when winterizing, but I also flush with clear water on the hose after each use. Last month I actually came in too close to low tide and hit bottom. Fortunately it's all very soft sand/mud so no damage done and I was able to back off the shelf at idle. No harm done and boat behaved no differently afterwards. Shame it gets so shallow, and gets worse later in the season which is why it got me, but the EPA won't let the owner dredge as often or as deep as he'd like... Which is retarded. You would think a marina would have water at all times but that is not the case. Oh well. Good luck solving your problem.

[jzelt]

When our's was rich (due to bad throttle position sensor, just dumping fuel at idle), the exhaust was black.

I am thinking this time of year, white steam is normal exhaust vapor.
Our bog was fuel filter, and the more it ran the lower the max rpms (was 3500, then 3000, then 2500 rpm), so in your case, I am hoping this is just a coincidence.