225 promax with one piece adapter plate

[90 5.0]

think thats a 2.5....."Opti"

Yeah was wondering why that was put up?

[Steve Pope]

I will be lifting a modified 2.5 150 power head off a 2.4 1 piece exhaust plate soon. I can post some pics of what we did to be able to use popet valve and thermostat cooling( standard steel bore engine cooling) It's quite simple . I am surprised at the number of posts that show up on this site that say you can't use a one piece plate with thermostat cooling.

[transomstand]

I will be lifting a modified 2.5 150 power head off a 2.4 1 piece exhaust plate soon. I can post some pics of what we did to be able to use popet valve and thermostat cooling( standard steel bore engine cooling) It's quite simple . I am surprised at the number of posts that show up on this site that say you can't use a one piece plate with thermostat cooling.

Probably plugged the poppet opening, drilled a dump hole in the block and restricted the plate dump holes to build enough heat.

[Steve Pope]

All the mods are in the plate, block is stock. You can mount any poppet valve small block powerhead to the plate except the early pre 80s with the kidney shaped exhaust.

[transomstand]

Then you would have to create a poppet cavity in the plate.

[Steve Pope]

Yes, create a popet cavity with a water dump passage straight out the bottom. Plug up the existing water drain holes and drill 2x 1/8" drain holes to allow powerhead to completely drain.

[PanRonnie]

Yeah was wondering why that was put up?

Non poppet steel sleeve engine

[transomstand]

Yes, create a popet cavity with a water dump passage straight out the bottom. Plug up the existing water drain holes and drill 2x 1/8" drain holes to allow powerhead to completely drain.

Love to see the photos. Do you weld in aluminum or build it from epoxy?

[Steve Pope]

There is another way to use a popet and thermostat on a one piece plate. If you are using a lightweight or performance cowl pan, weld plugs in 4 of the base plate holes, the ones that let water out of the powerhead and into the exhaust plate. This way the water has to pass through the poppet in the block. You do not need to modify anything else.

[transomstand]

There is another way to use a popet and thermostat on a one piece plate. If you are using a lightweight or performance cowl pan, weld plugs in 4 of the base plate holes, the ones that let water out of the powerhead and into the exhaust plate. This way the water has to pass through the poppet in the block. You do not need to modify anything else.

Think I like the other idea better.

[bigboy]

Thanks Steve

Would like to see some pics of the modified adapter.

I always thought it was not good to mount a 2.5 on a 2.4 adapter. Other way should be no problem.

Did you have to modify the exhaust in the adapter? 2.4bp should be bigger than the 2.5 fishing block?

Thanks

[Steve Pope]

The modified base plate does work but modifying the exhaust plate is better. I have never fitted a stock powerhead to a one piece plate, they have always been modified in some way and always had the exhaust openings opened up to match the exhaust plate.

[Steve Pope]

Sorry, forgot to mention that will be about a week before I get the powerhead off and pics posted. Cheers

[ChrisCarsonMarine]

Thanks Steve

Would like to see some pics of the modified adapter.

I always thought it was not good to mount a 2.5 on a 2.4 adapter. Other way should be no problem.

Did you have to modify the exhaust in the adapter? 2.4bp should be bigger than the 2.5 fishing block?

Thanks

[ChrisCarsonMarine]