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Lost 1000 rpm

F

floatin radio

Regular Contributor
1990 searay 17' 3.0 alpha 1. 17 pitch prop Carbed. Ok, a little back history that may be relevant.
About 4 years ago I gutted the interior and replaced the stringers, floor and the foam (aero marine ). Re fiberglassed everything. I did not redo the transom. Replaced gimble Berring and all bellows. It has been running fine since, gets up on plane, pulls 3 tubes, pulls skier.
Last time out last year I noticed I as only getting about 3500 rpm, it still gets up on plane but lost mph and 1000 rpm. I replaced all fuel filters , carb, inline and in fuel pump, also replaced anti siphon . Didn't make much difference. I was going to rebuild carb over the winter but never got around to it.
I took it out a couple weeks ago for the first time and was hitting 4300 rpm and it was running well. We floated and swam more than we cruised. When I was heading back to the dock, I had lost the 1000 rpms again. When I pulled the boat out of the water and pulled the plug, about 2 gallons of water came out. Bilge pump never kicked on while we were on the lake, ( 6 hours)
have t checked timing or replace plug wires, cap rotor or points in 4 years.
The foam I put in it was marine grade high density ( doesn't absorb water, or at least not as fast.
is it possible that my transom is where the water is coming in from and is soaking up the water causing it to be waterlogged?
Only two gallons comes out, where ( if any) is the rest of the water? Or is this old engine related?

thanks
 
I'm on salt water so it's worse, but I never get 3 seasons on a cap/rotor, and I've had them go from OK running to really crappy over a 2 day unused span, i.e. launched and run OK on Thurs afternoon to run really crappy on Saturday am.

There is a seal on Mercs that if it fails will let water in your boat.
Most bilge pumps will ignore 2 gal of water in a bilge. They "work" on height of water in bilge, not amount.
 
I have an older (late 1970's Silverline) with an Alpha one sterndrive, bought the boat in March. The gentleman I purchased it from is older and stated he did have a small water issue and what he did was silicone around the area where the Sterndrive attaches to the Transom which cured the issue for the most part, I found after four hours in the water there was a small amount of water in the bilge but never worried about it as I do not leave it in the water. Sunday I blew a trim line and replaced it, I discovered two things during repair, the trim manifold on the stern drive had a very small crack and no gasket so I replaced it and installed a gasket, was out yesterday for about five hours which included the boat sitting in the water for about an hour, when I took it out and pulled the plug there was no water at all so I am assuming this was the issue, it's an easy repair, just make a note or take a picture of how the hose(s) are attached.

As for the RPM, first thing I would do personally is when the boat is at a lower RPM yet one believes full throttle, have someone else drive and then check to ensure the carb is at full throttle as you may have something going on in the linkage.

All the best
 
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