Chronic promax overheat

[Esad777]

Hey guys I have a 2001 bullet 21xd that I bought used in 2005. It has a bone stock 2000 promax 225 with torqemaster lower. The motor with a new impeller every year will run without overheating in winter and spring water temps at 70 degrees and lower. When I try to run the boat in the summer with near 90 degree water temps the motor overheat alarm goes off at fast idle to roughly 55 mph. So during the summer I have to idle(145 degrees) or drive near full speeds(170 degrees) to not overheat. This has been happening since I bought the boat and I have spent over 5 grand over the years with mercury mechanics trying to fix it. Water pumps, poppets, time and time again, timing retarded. Motor lowered a hole, 120 degree t-stats to even having the power head removed, passages checked and all new gaskets installed. I have been told that the torqemaster that I have with the 4 intake holes on each side with the Stainless scoops is what causing my problems and that I need to spend the money on having low water pickups added. I just want the boat to cruise around and get me to the next fishing hole. Is the lower unit I have not capable of this without aftermarket additions? I have temp gauges on both heads and the right side is the one that kicks off the overheat alarm first.

[pappa pete]

Check the adapter plate mine started leaking and didn't know it because of lower cowl covering it up, burned up couple pistons quickly, promax also

[XstreamVking]

I would borrow a stock lower to try before I went any further. If no improvement with that. Maybe try a short idle and run (make sure it is up to temp) without the t-stats. This would verify that you are getting enough water flow. Sure sounds like there is a restriction somewhere or maybe hot exhaust getting into the block. (exhaust divider) Clear hoses on heads to check for bubbles/flow is also a way to check what you have going thru. I have had one engine that would run better w/o t-stats. It was a hot tempered bridgeport. Ran right on 145 but had to idle for a while to come up to temp before planing off. Good to have the dual temp senders...

[Esad777]

I do want to add that when the temps get high, it takes a long time to cool down. Like there is a lack of volume or a heat transfer problem. Say I'm on plane and the overheat alarm sounds. I'll shut down and idle for at least 5 minutes or more to get the heat to come back down to a window where I can jump back to the safe 55 mph or faster. Very slow to cool.

[rock]

Have you removed the scoops to see if it matters?

Rock

[Dave S]

Hard to cool with warm water. How do the water PSI #s look thru the rpms? Retarding timing holds temp up.... still burning.

[eli]

Air in the system will make hot Situation. Hook up 6 feet clear vinyl off t stats cover off have someone hold hoses in back go for ride check for bubbles and take temp gun measure water temp coming out of hoses while under way. Ever remove head gaskets check for sand around cylinders

[Greg G]

Sounds like there is an adapter plate issue to me as well

[Esad777]

Have you removed the scoops to see if it matters?

Rock

Yes, back in the first few years after I got the boat and when I was dumping a ton of money trying to have the issue fixed, I did remove the scoops and if I remember correctly it was quick to overheat. I believe the first mechanic tried also.

[Esad777]

Yes the heads have been off when the powerhead was removed to be checked for blockages and faulty gaskets.

[Motv18]

Sucking foam off the transom. Some would call it dirty not clear or clean.

Lwp or drop below the turbulance.

Thats my imiddate reaction if you’re reading 170 you shouldn’t be able to touch the pee stream. If it’s only warm then some flow issue is happening

mtbe second thing I saw was temp sensor replacement I imagine they have but...