Bad case of Bravoitis - changing to thru-hulls

[Rick]

Will be changing from outdrive raw water pick-up to thru-hull. I have 2 questions for those who have done it:

1. If using a clam-shell style pick-up do I still need to use a strainer?

2. Will the 1 1/4" opening provide too much water pressure for the impellor? Does it need to be restricted prior to the raw water pump like Merc does with that POS plastic tube that goes thru transom?

My boat is a '07 31PC 6.2L MX MPI with BIII's

 

[gixr04]

I suffered the same..... bit the bullet and installed 1 1/14 thru hulls. Best upgrade. No restrictions needed. I cut and capped hose at inside transom plate

 

[2006_31PC]

When I did mine I used clamshells and also installed strainers. It's amazing how much small junk still ends up in the strainers. I installed them under the bilge steps, mounted to the forward bulkhead on my 31pc.

 

[Rick]

When I did mine I used clamshells and also installed strainers. It's amazing how much small junk still ends up in the strainers. I installed them under the bilge steps, mounted to the forward bulkhead on my 31pc.

Thanks for reply.
I've read on discussion boards that when using a scoop thruhull that it forces too much water and pressure thru the raw water pump and can cause problem with impellor and possibly force water into the engine?? Some say you need to turn the scoop facing aft?? Doesn't seem right to me
Is your scoop facing forward or aft?

Also, since we both have 31PC's, where did you locate your thru hulls?
Thanks so much!

 

[2006_31PC]

Thanks for reply.
I've read on discussion boards that when using a scoop thruhull that it forces too much water and pressure thru the raw water pump and can cause problem with impellor and possibly force water into the engine?? Some say you need to turn the scoop facing aft?? Doesn't seem right to me
Is your scoop facing forward or aft?

Also, since we both have 31PC's, where did you locate your thru hulls?
Thanks so much!

My clamshells are facing forward. If there was too much pressure and water was forced past the impellor, the only place it could go is the normal route where the impellor pushes the water....that cannot damage the engine.

I was going through 1 to 2 impellors per season before I switched to thru-hulls. after that I just replaced impellors after 2yrs as preventative maintenance. so it was well worth it for me.

I mounted the thru-hulls up higher on the hull because i was afraid to interfere (or interrupt) water to the props. I'll try to find a picture. But I went just further outward (towards side of boat on the V) of where the generator pickup is.




Here is a pic that formula sent me on where they are mounted on a 37 with V drive...

 

[AllDodge]

My opinion
Bravoits is an issue in salt, but if the new style connection hose fittings are used, there should not be an issue for as long time.

That said strainers do help for a salt water boat. Tpenfield installed things on his 330

 

[Rick]

My clamshells are facing forward. If there was too much pressure and water was forced past the impellor, the only place it could go is the normal route where the impellor pushes the water....that cannot damage the engine.

I was going through 1 to 2 impellors per season before I switched to thru-hulls. after that I just replaced impellors after 2yrs as preventative maintenance. so it was well worth it for me.

I mounted the thru-hulls up higher on the hull because i was afraid to interfere (or interrupt) water to the props. I'll try to find a picture. But I went just further outward (towards side of boat on the V) of where the generator pickup is.

View attachment 10842




View attachment 10843

Thanks for the response! I took the leap today and drilled a hole in my boat!! Went well...I moved it approx 1' toward centerline from generator thruhull.
Cut the water hose in the outdrive and used a plug and double clamped it. Just so you have all the facts...my thru transom plastic Merc p.o.s fitting was soooo clogged with salt and collapsed that when I removed the inlet hose from raw water pump and put rabbit ears on outdrive, NO water even trickled into my bilge!
So...did a lot of the prep work today and ready to assemble. Thanks for your input on the orientation of the scoop fitting...was a bit nervous after reading some other posts on other sites.

Here is a pic that formula sent me on where they are mounted on a 37 with V drive...

 

[gixr04]