shakedown after changing bellows, need some help

[rad1026]

1989 Merc 5.7 with Alpha 1, gen 1. Changed all bellows and water intake hose two weeks ago and finally got out to the lake this weekend. I was anxious to see if I did a good job with my first time bellows job. Boat sat in the water with the outdrive up for several hours before I really took a run and I checked the bilge and no water. I was so happy. Took the boat for a little run around the lake, came back and checked the bilge again, I took on about three inches of water. I anchored the boat and cleared the bilge and couldn't see any leak. The boat sat all night in the lake and didn't take on any water, but as soon as I get under way it seems to leak. Not a ton of water, the pump has no problem, but I need to figure out where this is coming from. I'm going to pull the outdrive tonight just to make sure I have no water in the bellows, but how could it sit in the water all night and not leak, if it was the bellows wouldn't it leak even when not under way? Is there anyone who has experienced similar leak problems while under way only? Thanks for the help!

 

[Haut Medoc]

Re: shakedown after changing bellows, need some help

Can you run the boat on land on muffs?.....
That might help to isolate if it is an in the water problem or a cooling system leak.....
Some boats also tend to keep water in their bilge up front, but it comes aft when you plane up....
Just something to think about.....​

 

[rad1026]

Re: shakedown after changing bellows, need some help

I ran it on muffs for quite a while before I went to the lake and didn't notice water in the bilge, hmmm, but now that I think about it I had the plug pulled so any water would have just drained out back. You know I thought about the water collecting up front and moving back when I plained out. Its kind of strange my chaparral has a build in swim platform on the back that is completely over the outdrive and while I had my head stuck back in the engine compartment I noticed water sloshing around back in where the swim platform is. Its hard to explain how the compartment is designed but there are two large sections on each side behind the engine. My starboard compartment had water in it. It rained really hard Friday evening but I had my boat covered with the camping enclosure but I suppose water could have found its way back there from the rain. Its hard to even see how water could have gotten back there and I have no idea how deep that compartment is. I imagine it is at least a foot deep and sectioned off with a wall where the steering hydraulic cylinder is attached. If water was filling that compartment it certainly could splash out and in to the bilge. I really need to get my head back in there and look at that. Its going to take a magician to get back in there.

 

[stevieray]

Re: shakedown after changing bellows, need some help

Description of your transom/swim platform sounds a lot like mine (see my avatar picture). You may have a leaky hull-to-deck joint - if it sits close to the waterline it will dip under water when she tilts up to come on plane, and the following wave will swamp it when you come off plane. While in the water, stick your head in there & have someone walk around the swim platform - you should be able to hear the incoming water. If so, remove the rub rail & seal her up.