Overheating Promax suggestions

Got a 150 promax with a coned CLE on my ventura that is having some overheating issues. I have done quite a bit of research but any other thoughts would be appreciated. Has a stock cooling system (as far as I know), but is running 1/8in restrictors (factory) instead of thermostats. So far I have pulled the powerhead to check for blockages, checked poppet (found missing dounut and replaced), checked nosecone, all new waterpump. Motor has quite a bit of flow out the pee hole, water temps with heat gun around 125 at idle within 1 or 2 minutes. Water from top of block is luke warm. Temp guage at dash gets to 155 within 45 seconds of being on plane (too afraid to push it). The heads at idle and after a run are too hot to touch for more than 1/2 a second, this is the part that concerns me, have heard you should be able to touch for 2ish seconds.


Running 3lbs of pressure at idle and about 8-10 while on plane, have not been over 5k.

Connected cooling tube straight up to garden hose and still saw 110 degree water temps and the heads were nearly too hot to touch so I don't think it is a gearcase issue.

My thoughts for what it could be: 1. Dumping too much cool water from top of block 2. Restriction in head? 3. Poppet not opening properly

Uhhhhhhh, I think you been knockin yourself out for almost nothng. Be VERY careful about "stuff you hear".

I'd like to see a little more pressure, but other than that, you don't seem to be in great difficulty. That motor came from the factory with stats, not washers which would give you more pressure. Head temp of 155 is perfect and could even run 10 degrees hotter.

When was the last time it had a water pump kit?

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Originally Posted by transomstand

Uhhhhhhh, I think you been knockin yourself out for almost nothng. Be VERY careful about "stuff you hear".

I'd like to see a little more pressure, but other than that, you don't seem to be in great difficulty. That motor came from the factory with stats, not washers which would give you more pressure. Head temp of 155 is perfect and could even run 10 degrees hotter.

When was the last time it had a water pump kit?

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Thanks for the thoughts. Like I say, it is at 155 after about 45 seconds of running and haven't wanted to blow the thing, so I should probably see if it tops out there or quickly goes up to 170+. The block seems pretty damn hot from engines I've seen in the past (wish I would have checked with heat gun but only felt by hand). I just put a full pro marine water pump in while troubleshooting last week (new impeller, base, gaskets, the whole deal). The o ring on the baseplate was split in 2 when I pulled it so I was hopeing that was my issue but it didn't change anything in terms of temp or pressure.

I think I'll probably throw some 143 stats in it and see what it does, my only concern was if that would make it run even hotter at idle by not dumping the water right away.

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Originally Posted by transomstand

Uhhhhhhh, I think you been knockin yourself out for almost nothng. Be VERY careful about "stuff you hear".

I'd like to see a little more pressure, but other than that, you don't seem to be in great difficulty. That motor came from the factory with stats, not washers which would give you more pressure. Head temp of 155 is perfect and could even run 10 degrees hotter.

When was the last time it had a water pump kit?

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Agree your not to hot. Everything you said sound perfectly normal to me also. Try throwing some t-Stats in a run it? If your water temp at the lake is above 75 deg you may try bigger washers but i wouldn't want to be much cooler than you are now really. The to hot alarm goes of at 240 i think? So as long as your below 180 or so your golden. Even 150 on the heads is hot to touch for some. Especially my wife! haha Kidding. :D Do your self a favor and get a heat gun with a digital read out. That way you can compare the gage to the head temps. Generally heads will shoot hotter than gage buy a little. Just went threw the same as you. i would push it more than you are. if your gage is correct then see if you can make it get to 170. If you cant then I would have a great summer and drive her like ya stole her! You can also install bigger washers if your concerned about 155 I would not be though. Check out the ones i just tried out under technical discussion they are sick and have all sizes depending on water temps at the lake! awesome!:thumbsup:

how warm is the water you run? Anything 75 and up will for sure make run warmer. 3/8 washers is what i hear more than 1/2 inch in warm water?

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Originally Posted by JCSmile

Thanks for the thoughts. Like I say, it is at 155 after about 45 seconds of running and haven't wanted to blow the thing, so I should probably see if it tops out there or quickly goes up to 170+. The block seems pretty damn hot from engines I've seen in the past (wish I would have checked with heat gun but only felt by hand). I just put a full pro marine water pump in while troubleshooting last week (new impeller, base, gaskets, the whole deal). The o ring on the baseplate was split in 2 when I pulled it so I was hopeing that was my issue but it didn't change anything in terms of temp or pressure.

I think I'll probably throw some 143 stats in it and see what it does, my only concern was if that would make it run even hotter at idle by not dumping the water right away.

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Curious, what do you consider normal temp?

Also want to confirm we're measuring head temp and not water temp.

Anyone remember the temp sensitive wax "crayons" that were used to check for overheating or hot spots before the days of digital anything?

Every time I read one of these threads I recall a Merc rep friend years ago ( 30 years or so ) telling me about these. Never seen any...

Not wanting to jack the thread....just wonder if any of the "seasoned" guys recall these?

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Originally Posted by W2F a V-King

Anyone remember the temp sensitive wax "crayons" that were used to check for overheating or hot spots before the days of digital anything?

Every time I read one of these threads I recall a Merc rep friend years ago ( 30 years or so ) telling me about these. Never seen any...

Not wanting to jack the thread....just wonder if any of the "seasoned" guys recall these?

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They still make em

https://www.mcmaster.com/#temperature-markers/=18ec0ol

Need to check the temp with a heat gun. 130° will seem smoking hot to the touch.

Have to also make sure you are running the proper temp sender for your gauge. I had some merc gauges in my boat and when I'd hook them up to the factory temp sender in the head they'd show 30° warmer than the actual temp. Found out later that those gauges required the brass temp sensor like is in the hipo heads (1/8"npt)

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Originally Posted by whipper

Agree your not to hot. Everything you said sound perfectly normal to me also. Try throwing some t-Stats in a run it? If your water temp at the lake is above 75 deg you may try bigger washers but i wouldn't want to be much cooler than you are now really. The to hot alarm goes of at 240 i think? So as long as your below 180 or so your golden. Even 150 on the heads is hot to touch for some. Especially my wife! haha Kidding. :D Do your self a favor and get a heat gun with a digital read out. That way you can compare the gage to the head temps. Generally heads will shoot hotter than gage buy a little. Just went threw the same as you. i would push it more than you are. if your gage is correct then see if you can make it get to 170. If you cant then I would have a great summer and drive her like ya stole her! You can also install bigger washers if your concerned about 155 I would not be though. Check out the ones i just tried out under technical discussion they are sick and have all sizes depending on water temps at the lake! awesome!:thumbsup:

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I think trying to push it might be a good idea. I have plenty of the factory thermostats and washers so I can play with that. If not, quarters and a drill bit work well too :D. I have a little digital infared scanner, I just was reading water temp with it and not head temp (stupid!). I would guess our lake temp is probably in the low 80's as it's only 25 feet deep and Iowa is pretty hot these days.

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Originally Posted by transomstand

Curious, what do you consider normal temp?

Also want to confirm we're measuring head temp and not water temp.

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Yes, I am using a new livorsi "water temp" gauge connected to the tan wire for the head temp probe on the starboard head (between cylinders 1 and 3). I guess I consider normal between 140 when the t-stats open and 160? Once I get above 155 I start worrying, perhaps I'm premature? considering this is a steel bore on a 2 piece adapter and not nic bores on 1 piece running with hi-po cooling.

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Originally Posted by mach351

Need to check the temp with a heat gun. 130° will seem smoking hot to the touch.

Have to also make sure you are running the proper temp sender for your gauge. I had some merc gauges in my boat and when I'd hook them up to the factory temp sender in the head they'd show 30° warmer than the actual temp. Found out later that those gauges required the brass temp sensor like is in the hipo heads (1/8"npt)

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Thanks I will check that. My dad has been a livorsi dealer for years and we have run them with the standard temp sender, but I will verify. Next time I run it I will use the temp gun on the heads and cylinder walls.

I would check that the sender works with that gauge correctly. I know for a factory that the autometer ones are different and I thought they made the livorsi??

YES my automaker gage is way off accually. almost 20degs high on the gage. I confirmed this back to back the day the original one went and always double check with infrared.

BTW JCSmiles honestly I wish my 225 promax would never go above 155 but it always has and im sure always will. The last thing you want is a cold size so warmer isn't such a bad thing. For your surface water temps, and if after you hit the heads with the lazer, and in fact your over 165-170 then just put a bigger hole in the washers. Also faster is cooler. For me anyway. 6000-6500 rpm i run cooler than 4500-5000 rpm with T-Stats. that is not the case with the Washers now though. For 80+ deg lake water temps i wouldn't even bother trying the t-Stats because they will be even hotter. i would just step up to the next size washer but {only} if your hotter than you are because honestly yours sounds great!!