5.7 Mercruiser Hydrolocking Problem

[sailsmanship]

Have a 97' 5.7l Mercruiser w/ Alpha One drive. Have a hydrolocking problem. Manifolds and elbows replaced two years ago. Run in freshwater only. Thought I had it fiqured out. I replaced the elbow gasket that looked like it had a water trail on it. Now if I go out and run and come back to dock, no problem, even if I come back out to the dock days later, no problem. But if I go fishing and float in the water for awhile tossing about very little, go to start, BANG.... hydrolcked. Bump starter for a little bit, then it will start and run fine. Any ideas where I might start to look where the water is coming in at?

 

[Don S]

Re: 5.7 Mercruiser Hydrolocking Problem

Sounds like too much weight in the back of the boat and the water is getting in thru the exhaust. Merc makes riser extensions for 3 and 6" rise.
What you need to do is get everything on the boat like you were fishing and measure how high the top of the risers are compared to the water line. (KEEP IT RUNNING WHILE YOU ARE MEASURING)
I will post shortly on how to measure that.

 

[Don S]

Re: 5.7 Mercruiser Hydrolocking Problem

Go to pages 11 and 12 in the installation manual below.

http://www.boatfix.com/merc/Install/gas/86016900.pdf

 

[sailsmanship]

Re: 5.7 Mercruiser Hydrolocking Problem

Had boat for 4 years now with no problem at all. Same gear and people that go fishing with me. ( maybe a little weight gain ) Ha Ha. Why would it do it now. I will say this though, I have always noticed that it sat low in the water.
The water line comes up to the Alpha one logo on the back of the outdrive, hardly any outdrive showing. Still, why now?

 

[Don S]

Re: 5.7 Mercruiser Hydrolocking Problem

The wood in the transom could be soaked, foam could be water logged, impossible to say without actually looking and checking. If it's that deep in the water and the shutters are bad and it rocks enough, yea, you could get water in the exhaust. Do the measurements and see where you are at.

 

[sailsmanship]

Re: 5.7 Mercruiser Hydrolocking Problem

Thanks, but I can't open the file. I download it but nothings there. I don't know if I'm doing anything wrong.

 

[Don S]

Re: 5.7 Mercruiser Hydrolocking Problem

It's a .pdf file. May be your firewall, or spam blocking software, who knows. But it does work, I just checked it, and all 3.18MB downloaded and opened fine.

 

[HT32BSX115]

Re: 5.7 Mercruiser Hydrolocking Problem

Thanks, but I can't open the file. I download it but nothings there. I don't know if I'm doing anything wrong.

Make sure that you have (the latest version) Adobe Acrobat Reader installed
(Select the correct operating system etc)
http://www.adobe.com/products/acrobat/readstep2_allversions.html

After you follow the instructions to install Acrobat Reader,

Right click on the following link, select "Save As" and select save to desktop.

http://www.boatfix.com/merc/Install/gas/86016900.pdf

After it's on your desktop, double click the file.

Regards,


Rick

 

[sailsmanship]

Re: 5.7 Mercruiser Hydrolocking Problem

Thanks, It was the Firewall. Couple questions. First, how can you accurately measure the distance from the waterline, it being on the outside, and the elbow on the inside, only thing I can think of is using top of gunwal as a reference point . The engine is in a doghouse and sticks above floor level.
Two, if it is too low, which spacer should be used if both will bring it into specs. I'm thinking 6 inch if exhaust bellows will reach, since taller the less likely for water to back up.

 

[sailsmanship]

Re: 5.7 Mercruiser Hydrolocking Problem

Also, Are the shutters located inside the "Y" pipe by the transom ?.

 

[Haut Medoc]

Re: 5.7 Mercruiser Hydrolocking Problem

Also, Are the shutters located inside the "Y" pipe by the transom ?.

Yes, they are located in the top of the y pipe, just below the elbows....

 

[Don S]

Re: 5.7 Mercruiser Hydrolocking Problem

Shutters do not seal enough to prevent water from getting into the engine if the risers are too low.
Here's a picture of how to measure the riser heght. The drawing is from a Volvo manual, but the process is the same for any engine type.

 

[Fishermark]

Re: 5.7 Mercruiser Hydrolocking Problem

It's interesting that Volvo calls for a minimum distance of 14" while Mercruiser says that 13" is the minimum. I guess Volvo is more cautious!

Another method to use is the clear hose method - it may be easier: (In order to use this method you need to put the entire hose under water and block the end you remove from the water till you get it in the boat and above the water line).

 

[sailsmanship]

Re: 5.7 Mercruiser Hydrolocking Problem

Thanks for the info, it's out to the marina on Monday to check.......

 

[sailsmanship]

Re: 5.7 Mercruiser Hydrolocking Problem

Checked it yeserday and the distance was 14.5 inches. Guess I will have to start tearing it down..... Thanks for the help......