Has Anyone Modified Imco Shorty For More SWater Flow?

[CRC]

Just as I trim up enough to start lifting the bow my water pressure drops and the horn sounds. Imco suggested opening up the front of the water inlet. Has anyone done this? I'm running a 525 efi which requires about 25 psi minimum water pressure at speed. Pics:

 

[Trim'd Up]

Most people have too much water pressure with IMCO lowers. Is that how they told you to enlarge it?

 

[htrdlncn]

25psi minimum?
I had no idea they needed that much, would have thought
that would be bad for the gaskets, I freak when mine goes over 20lbs
but its not efi..

 

[PatriYacht]

I bet radiusing that sharp edge at the front would improve waterflow alot. It's pretty rough looking.

 

[CRC]

The 525 is closed cooling. This is raw water pressure. I've done some research and it does need a lot of pressure; Don't know why. Here is one post: http://www.offshoreonly.com/forums/2629265-post5.html Yes, Imco suggested opening up the slot to the front. I wondered if anyone else has done this and could post results or pics before I start grinding. The alternative is a transom mount water pick-up and filling in the lower. I don't know how I would fill in the lower and have it hold up other than being disassembled and welded.

If no one else here has done this mod then I guess I'll be the guinea pig and post pics and results....

Boat is a 22 Donzi Classic. Prop is 30p Bravo 1 from Brett. Top speed 85. Best to date, 85.8.

 

[gcarter]

Hi Carl, I think if you install the transom pickup, you'd best leave the lower pickup open because the drive needs the cooling water.......
Instead, reach inside the bell housing and cut out a section of water hose. Let it flow into the bell housing area, it's a simple fix.
Then, install one of these, and its gasket, on the inside of your transom to replace the hose fitting;

 

[CRC]

OK, thanks George. I'm going to try opening up the inlet first though. I'll do it before I head out again. It should only take a few minutes with the air grinder and will be a much easier fix if it works.

 

[Racerguymiami]

As mentioned earlier, the imco lowers normally have ample water pressure. Just curious as to your trim angle when you start to lose water pressure? If you went from standard drives to shorties it might be that the drive is too high and you're overtrimming to get the bow to lift to get the boat to break loose. If it's overtrimmed all the grinding in the world won't help, the water pickup will be behind the bullet and out of the path of oncoming water. Just my .02 cents. You may want to run the boat out and when you lose water pressure, stop the boat, look over the transom and see what angle the drive is trimmed to relative to the boat bottom.

 

[Madpoodle]

I would double check the pressure sensor first. Is there somewhere to temporarily install a manual gauge? I also have to agree with the plan from Racerguymiamuh

Carl, if you decide to get a transom mount, let me know and I'll ship one of Stainless Marines out to ya.

 

[CRC]

I would double check the pressure sensor first. Is there somewhere to temporarily install a manual gauge? I also have to agree with the plan from Racerguymiamuh

Carl, if you decide to get a transom mount, let me know and I'll ship one of Stainless Marines out to ya.

I don't know about being able to check the pressure but might get back on the transom mount. Thanks.

 

[DAREDEVIL]

As mentioned earlier, the imco lowers normally have ample water pressure. Just curious as to your trim angle when you start to lose water pressure? If you went from standard drives to shorties it might be that the drive is too high and you're overtrimming to get the bow to lift to get the boat to break loose. If it's overtrimmed all the grinding in the world won't help, the water pickup will be behind the bullet and out of the path of oncoming water. Just my .02 cents. You may want to run the boat out and when you lose water pressure, stop the boat, look over the transom and see what angle the drive is trimmed to relative to the boat bottom.

:iagree: 100%

 

[gcarter]

I don't know about being able to check the pressure but might get back on the transom mount. Thanks.

As has been noted elsewhere, how about the oil cooler drain? It's 1/8" pipe thread, I think.

 

[PatriYacht]

Mine lose pressure at high trim angles also. Have to trim it pretty high though. Maybe a better solution would be to modify the props for more bow lift. Or chang to a 5 blade.