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Discussion Starter · #1 ·
my v-drive flat is overheating,the water pump impeller checks fine and water flows thru motor at idle fine but at speed the temp just climbs past 180 and will run upwards of 210 or more if i dont shut it down,engine is hot! steam is rolling out the over flow but water stops flowing out overflow after it gets to about 180. it's like the pumps stops pumping for some reason after a cooldown the pump flows water at idle just like it should.
pulled pump cover and impellor is fine,checked and flushed all lines for obstructions and found none. you would think the water being pushed thru the water strainer alone @ speed would be anough to keep it cool ?
new motor 565 alum heads,34 locked out timing full msd system,dry headers,pump gas
have had this flat for over 30 years with the same water system and it has never ran hot. anyone?
 

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Sometimes the impeller looks good, but is weak.

What type of pump do you have, and when was the last time you changed the impeller? A good test would be to remove the impeller and hook up a garden hose with good pressure to make sure there is not an obstruction. Have you back flushed?
 

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Discussion Starter · #3 ·
impeller is a year old and looks new still, back flushed all the lines yesterday
also pump is a 1'' pump from rex marine with a splined shaft deal
water flows out of the overflow fine while idle but when the motor is hot there is zero to little flow, after motor cools it has a normal stream again. almost has to be something restricting flow in the v-drive box (water cooled)
guess that will come apart this weekend, just spent ten days on the lake and i have so many header burns on my arms it's not even funny.
 

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impeller is a year old and looks new still, back flushed all the lines yesterday
also pump is a 1'' pump from rex marine with a splined shaft deal
water flows out of the overflow fine while idle but when the motor is hot there is zero to little flow, after motor cools it has a normal stream again. almost has to be something restricting flow in the v-drive box (water cooled)
guess that will come apart this weekend, just spent ten days on the lake and i have so many header burns on my arms it's not even funny.
Check the timing
 

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Precision Craft Marine
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Also, check your hoses, sometimes they will suck up closed. I have also seen this happen with pin holes or "Braid holes if you will" from the braid poking the inner hose. The holes cause the pump to suck air.
 

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QUICKIE
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Keeping water it the heads

I have a Hondo Blown gas 505 bb.Did the same thing/ found it to b
too much water going through the water cooled headers . not enough back pressure to keep the heads full of water hence a vapor lock or steam pocket built up preventing the heads cooling properly. the water must go through the heads.I incresed the tension on the checkvelve problem sloved.:)bulb
 

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Discussion Starter · #7 ·
thanks for all the reply's
timing is 34 degrees and locked out
headers are run dry.no water to them at all
i am going to replace all the hoses this weekend and reverse flush v-drive with pressure washer and will test a different water pump i borrowed today.

wouldnt the water pickup take over at some point and force water though this pump?
 

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water

Did the ride of the boat change ? If the boat feels like it is out of the water more now then before your water pick up may be sucking air . Just went through this problem with my bezer . just thought i would through it out there
 

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Discussion Starter · #9 ·
Did the ride of the boat change ? If the boat feels like it is out of the water more now then before your water pick up may be sucking air . Just went through this problem with my bezer . just thought i would through it out there
ya the new engine 565 w/alum heads over the old 496 w/cast heads does run a bit more out of the water then the old setup
so what did you change to fix the problem?
 

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Some stainless tube and a little welding had to add about 5/8 " to pick up the first time then it turned out to be 1" to make it work right . This is a old trick some circle boat driver tought me about 20 years ago on rocket98s old boat Then on it was common practice when we built a new race boat . But i got in a hurry and forgot about it tell the boat was done and got hot on me Floating at lake to cool of is not fun .Check with rex to see what lenght water pic ups he has in stock
 

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If the impeller is a year old, it's definitely time to change it. It may or may not be the problem, but when they sit in the pump for that long they tend to lose their shape. While they appear to be in good condition, they may not pump much...

Hey... just a thought after my first bourbon!!! Have you pulled the impeller out and double checked the placement pin or keyway? I'm wondering if the impellor is working at idle, but slipping on the shaft at higher speeds?????

In fact, a good test on the hoses would be to remove the impellor, and run around to see if water runs through. If it does, it's the pump. if no water comes out, it's the cylinders welded to the pistons!:D
 

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If the impeller is a year old, it's definitely time to change it. It may or may not be the problem, but when they sit in the pump for that long they tend to lose their shape. While they appear to be in good condition, they may not pump much...

Hey... just a thought after my first bourbon!!! Have you pulled the impeller out and double checked the placement pin or keyway? I'm wondering if the impellor is working at idle, but slipping on the shaft at higher speeds?????

In fact, a good test on the hoses would be to remove the impellor, and run around to see if water runs through. If it does, it's the pump. if no water comes out, it's the cylinders welded to the pistons!:D
This my be a streach but ..Is the impeller installed backwards. I know this from personal experance that it will fit but won't work to well
 

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Discussion Starter · #14 ·
what size carbs are u using
dart single intake with 1050 dominator 95/95 square jetting , plugs look good,autolite ar2593 carter mech race pump -10 inlet and -8 to carb
i reset valves and reset fuel level sat eve and ran sunday morn and had same results of engine overheat in about 2 miles from dock.
i will say pulling a spark plug to check it in the middle of the lake will get me wet,and i have about 3/8 of a mile of no wake zone to get back to my dock so i may be a little off but not much. same fuel system pump and carb from last five seasons.but i see where you are going and i will recheck fuel setup since new motor demands more fuel to run.
Thanks
when the motor gets hot there is no water flow,and impeller has been checked three times last week i think ps 14 is on the right track my water pickup is old style brass water stainer type and i am starving the pump for water or there is a blockage in my v-drive
it's faster to change the engine then it is to get at that water pickup.i have six cat eyes burns on my arms and one on the back of my neck trying to fix this on the water waiting for it to cool down. oh ya i should thank the wife and kids for putting up with me for ten days.
 

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Discussion Starter · #15 ·
If the impeller is a year old, it's definitely time to change it. It may or may not be the problem, but when they sit in the pump for that long they tend to lose their shape. While they appear to be in good condition, they may not pump much...

Hey... just a thought after my first bourbon!!! Have you pulled the impeller out and double checked the placement pin or keyway? I'm wondering if the impellor is working at idle, but slipping on the shaft at higher speeds?????

In fact, a good test on the hoses would be to remove the impellor, and run around to see if water runs through. If it does, it's the pump. if no water comes out, it's the cylinders welded to the pistons!:D
thanks v-driver.i need a few also (drinks) pump is a splined drive 1'' pump and is the same pump i have run for twenty years and was a new impeller last year but you have a good point,i borrowed a magnaflow pump today and i am going to change out the old water pickup to something more modern this weekend and retest and i will try your test also before i change anything.

with the money i have in this new motor nothing would suprise me at this point.
 

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Discussion Starter · #17 · (Edited)
why is your water flow going through the v-drive and maybee you should up the size of your hose.
v-drive box is water cooled and came factory this way 1973 boat has always worked very well and has never had any overheat until this year, inlet is 1 '' then runs 3/4 to gearbox then run's into a tee and breaks into two 1/2 line into the timing cover and out t-stat housing overboard.
when engine is hot i checked overboard flow and there is little to none,just pissing steam and intermittent water burst. going to try the water pump and test like v-driver suggest time for a hose change and pickup/pump impeller upgrade.

but big thanks to all that has posted, think i will go to home depot and get one of those big magnet and dredge the lake for some thrown tools:D:D
 

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think i will go to home depot and get one of those big magnet and dredge the lake for some thrown tools:D:D[/QUOTE said:
hahaha.

sounds like me when shit isnt going my way and im just trying to have a good time and relax. anyway, Im sure you'll get it fixed and enjoy that new motor.

Let us know how it turns out.
 

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I think you have way too many cubic inches for your old cooling configuration. Bigger engines need a lot more water flow to maintain the same temperature as a 454 or whatever. When I went from a 350 to a 540, it just didn't work with a neovane and -8 hoses. Had to upgrade to a magnaflow and -10 lines throughout. I don't think it's going to be possible to pull water through the v-drive and split it from a tee to cool a 565. You will get low pressure and a steam pocket in the head. I would start over with a pickup on the cavitation plate, leave it about 1/2 inch long or more. Angle cut the feed pipe to aim it forward. Run -10 hose to the pump, which needs to be the full size magnaflow. Run -10 to the block. Use -10 for your overboard line.

If you can add a water crossover between the cylinder heads at the back of the intake this helps a lot to prevent steam pockets. I fought this for a month on a blown 540 before I figured it out.

Leave the old water pickup in place to feed the v-drive and add a dump out the bottom or bring it back to dump at the transom.
DJ
 
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