perfboat

This is my first post for my first perfromance boat. I bought a 1996 scarab 29, with a single 502 mpi, completely stock with 247 hours on it. I've had the boat for about one month and it started and ran flawlessly until about a week ago. It started to blow a little white smoke out the exhaust while at 2-4k rpm's, sometimes at idle if idling for extended periods. The engine is making a slight rattling noise (lifters?)on first start up but goes away when warm. Oil pressure is fine and no water in the oil. The weather has changed slightly with the air being slightly cooler and the lake water still around 83 degrees. Could it be a riser gasket or something exhaust related. The boat has the gil thru hull setup on it with internal flappers. Any suggestions would be appreciated

Dave M

I would go ahead and replace your riser gaskets. They are easy to replace. My engine just died partially due to a riser gasket failure. My manifolds and risers were only about 2-3 yrs old.

blue thunder

Changing riser gaskets is never a bad idea. Especially if you don't know their history. For what it is worth, my engines steam more now when cooler out. Not sure I would worry too much about that as long as the motor oil looks ok and it runs good. The internal flappers can make a hell of a racket upon startup until a flow of water consumes them. When I start my engines I listen for the rattle to stop because then I know I have water flow. They alway rattle a little even with water flow. Again, I would not worry until more symptoms ocurr.

Anyway, welcome to the board. Always good to have another fellow Scarab owner around

509 SC

I agree with Blue Thunder, I had my boat out today ( 502 MPI ) and noticed the steam was greater than norrmal but water and air temps are cooler in fall. I also notice more steam when I run in Lake Michigan which is like a bowl of ice cubes ! The rattling noise is most likely your internal exhaust flappers at idle. Stev

alter ego

I get a lot of steam from my 502. I've seen a lot of boats out lately with a lot of steam especially in the no wake zones. Do any of you notice a difference in the amount from one side to the other? I get more on my starboard side. Nothing abnormal in the oil just a little more steam.

Revd Up

I have a 99 502 MPI and get alot more steam out of the starboard side too. Usually after a hard run. Everything seems normal. Temperatures good.(180) I replaced riser gaskets didn't seem to do anything. If I place my hand on the riser, the port side is cool, starboard hot. Merc says this isn't uncommon. The Engine has about 60 hours on it and has done it since new. Seems like uneven water distribution to me. Any ideas how to run more water into the starboard side?

hillbilly24

It is not uncommon at all to get more water out one side than the other. water chooses the easiest path and due to casting variarions and corrosion buildup in manifolds,risers or elbows you will get more flow from one side than the other. If you have no flow out one side that is a problem though and you need to check for a restriction. First though if you dont know the history of the boat just service the seawater pump and see what that gets you. if still no flow from one side follow the water flow for that side until you find the problem. It could be a piece of an old impeller stuck in the t-stat housing, I have seen more than one engine meltdown cuased by that. Check all the hoses for partial blockages and then check the manifolds and elbows and as was stated previously just changing the elbow gaskets is never a bad idea as you have no idea of the condition of the internal ring of the gasket wich is the one that leads to chaos.

509 SC

Ditto on the starboard side steaming more, always been that way. Steve

Revd Up

I seem to be getting plenty of water out both sides but I will be changing my impeller this off season as well as check t-stat housing, hoses etc. to see if I can find any obstructions. Thanks, Steve

perfboat

Thanks to all of you for the input, I will be pulling my risers this afternoon and changing the gaskets. I will check for obstructions as well. There seems to be plenty of water coming out of the pipes. The steam just made me wonder if something was wrong. Maybe this is a good excuse to buy imco's exhaust over the winter.