225 promax with one piece adapter plate

[Greg G]

I went back and forth through the same rodeo and did a lot of research along the way. I found that for 90% of us, and the way we run our boats "non-race" that the one piece adapter and washers is annoying at best. I finally went to a 2 piece adapter, thermostats, and poppet on my 15" and (knock on fiberglass) have had zero problems this year. It's actually been a unique experience to have the dang motor just run and run. Never could get the cooling to work properly for two years prior.

[Go Time]

I concluded the same thing. If you don't need the one piece adapter to use wing plates for steering purposes you are better off using the 2 pc setup.

[tux974]

I concluded the same thing. If you don't need the one piece adapter to use wing plates for steering purposes you are better off using the 2 pc setup.

This is true but you can also use wing plates with a 2pc plate, just need the correct plates!

[Greg G]

I had a 2000 model factory 15 inch Pmax and it had tstats.

Hullbilly....Did it use the poppet valve also?

Yessir............failed to mention that mine had a one piece plate also.

When I was trying to get my problem solved, I communicated with two additional folks who also had factory Promax 225 SS motors that came stock with one piece adapters, 120 degree thermostats and poppet valve for idling. All 100% factory. One guy actually had bought his motor brand new and still had it. Just a couple more data points as there are VERY few factory SS motors out there.

[Greg G]

I went back and forth through the same rodeo and did a lot of research along the way. I found that for 90% of us, and the way we run our boats "non-race" that the one piece adapter and washers is annoying at best. I finally went to a 2 piece adapter, thermostats, and poppet on my 15" and (knock on fiberglass) have had zero problems this year. It's actually been a unique experience to have the dang motor just run and run. Never could get the cooling to work properly for two years prior.

I concluded the same thing. If you don't need the one piece adapter to use wing plates for steering purposes you are better off using the 2 pc setup.

Dragging it back to the top to continue the report.............

The 2 piece adapter has run very well for the two months since the last post. Idles well with the 120 degree t-stats and settles at 123-125. The minute I stab the throttle and come onto plane the temp drops very quickly as one would expect. Once up at 4000 RPM cruise the temp on the SCM 1000 gauge drops to 96 degree and even at WOT never goes beyond 102. Far colder than I'd like, but the senders are low on both banks so they are reading actual water temp. Has run like a clock with the 2 piece. I have given a fleeting thought to doing something to get the temps higher but then I realize I'm not sure what I would do to achieve this? Smokes a little more than I'd expect for the first 5 minutes or so burning Pennzoil exclusively.

[tux974]

If you are dropping temps that fast when up on plane you better off running the 143 stats. Steel sleeve motors need some heat. Your additional smoke is probably coming from the ECU telling is cold need to rich en up....JM2cents

[LongShot]

OK guys just rub it in....!!!! I am assuming the triangle opening in the two piece adapter shown is the missing chamber in the one piece plate that was discussed in the 225X? That chamber vents to the can instead of just being part of the water flow "loop" so the poppet does not have pressure equalized on each side.

[transomstand]

but the senders are low on both banks so they are reading actual water temp.

If you are reading actual water temp, then your temps are fine. Water temp is about 30° cooler than head temp.

[specboatops]

Appreciate this thread as I have a newly built 225 Pro Max, this thing had stupid water pressure, 45 PSI and above :O but now the thermostats and the popet have been removed, running fender washers. Am I just asking for problems down the road? Water pressure now is right where it should be, and I have 5 or 6 trips this year with no problems, but is it making enough heat ? I don't know.

[Go Time]

A 225 PROMAX on a factory promax 2 pc adapter with poppet and thermos has 3-5 PSI PSI at idles and ~ 15 PSI at WOT. I have two and they are both about the same and run very good with no temperature issues. These are 225 Promax engines.... NOT 225X motors. Don't want mix apples and oranges.

Dave, your observation on the open chamber resulting in no differential pressure across the poppet is correct for the one pc adapter. That's why the poppet is non functional with the one pc adapter.

[Greg G]

Appreciate this thread as I have a newly built 225 Pro Max, this thing had stupid water pressure, 45 PSI and above :O but now the thermostats and the popet have been removed, running fender washers. Am I just asking for problems down the road? Water pressure now is right where it should be, and I have 5 or 6 trips this year with no problems, but is it making enough heat ? I don't know.

I'd be looking for an obstruction of some sort with that type of crazy high pressure. Assuming you are a regular boater and not racing the thing, my .02 is go back to "poppet and stats" and find the obstruction. As has been said in the earlier post, the motors like heat and you are in colder waters to begin with. Of course the water pressure gauge could always be wacky but I suspect you checked that already.

[specboatops]

Correct, the gauge was the first thing I checked. Going back to poppet and stats this winter. No boat is not raced, just fun up and down the river.

[Greg G]

Correct, the gauge was the first thing I checked. Going back to poppet and stats this winter. No boat is not raced, just fun up and down the river.

Did you go back to a poppet and thermostats? Draggin it back to the top as you can never talk about adapters too much in the off season.

[Greg G]

And some more info up from the archives thanks to 2.5H .............

At the risk of poking a bee hive, all eight or ten 1996-2000 vintage 225 Promaxes in this neighborhood came with two piece adapters, including all three 15"ers. The only factory one piece Promax we've seen came on an extremely rare 20" Offshore Promax. My $.02 ....... Brad

[tlwjkw]

has anyone actually compared a "real pro max" one piece ta any other one piece???.. don't think merc would add a poppet that does nothin'.... unless you actually took tha 15" motor outta tha box then what ya have or what you've seen don't count!