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Old 10-12-2009, 15:38   #31
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For replacement pump/parts. WWW.depcopump.com.

If you have the pump thhat has the formed piping and o-rings

DO NOT BEND THE PIPES WHEN REMOVING!!!!!!!!!!!!!!!!!!!
AND GET NEW O-RINGS AND A FEW SPARES. "DAMHIKT"
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Old 10-12-2009, 16:44   #32
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Since repropping/repitching is what you changed I have a suspicion that it might be a bit over propped.

I had a friend with same problem who found a small fish in his intake after we took the hoses off.

regards,
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Old 10-12-2009, 16:52   #33
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Yeah, I missed the prop thing, since it didn't come to light until post #15.....

I'd still check the usual suspects....but the prop is definitely now on the list....
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Old 10-12-2009, 17:03   #34
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Sorry but this 2003 heat exchanger does not look like mine
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Old 10-12-2009, 19:15   #35
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(I had to post the picture on a blog b/c this forum wouldn't allow me to upload the image...it's a .gif format pic, not a .jpg, and I don't know how to convert it.)
Yeah! We can upload .gif pictures, just not over 400 KB.
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Old 10-12-2009, 20:10   #36
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Here's a new maybe dumb question - Is the fresh water circulating?
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Old 11-12-2009, 08:46   #37
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Here's a new maybe dumb question - Is the fresh water circulating?
Actually, that had occured to me, but I wasn't sure at all how to test it.

Last week, I spoke to a mechanic and they recommended I get a handheld infrared thermometer gun, the ones you guy at an auto parts store and use it to measure temp on certain areas of the engine while underway.

To see if the fresh water is circulating they said to measure the temp on the block before and after the thermostat opens (stat starts to opens at 164*F and is fully open at 189*F). Looking back at my notes from the other day when we ran the boat, I see that I only have ONE such temp measurement Argh! That day, I was measuring temps over time at the area where the temp sender is and comparing it to the gauge reading, then measuring temp of raw water into and out of heat exchanger, etc...we were raising and lowering sails, checking various things on the engine, etc. and it looks like I only measured block temp once...idiot! So it might not be useful info. Too bad I didn't do it several times, over time.

Anyway --here's what I have: when the area on the cylinder head around temp sender was 180*F (so, presumably the area where the hot coolant is inside the cylinder head is a bit hotter since the temp sender is in the liquid), the block was 194*F. These measurements were done after the engine had been running for an hour more or less. So, the block appeared to be hotter after the thermostat had been open for at least a while.

I guess this might --possibly-- suggest that that freshwater is not circulating, or not circulating enough --according to the mechanic I had spoken to (the one who recommended measuring temperatures). But I'm skeptical about trusting this temp measurement since I was dumb enough to only do it once! Argh...And, frankly, those handheld thermometer guns read a few degrees differently depending on how closely you hold them to the surface you're measuring...and the boat is moving, your arm and hand moves a little bit, etc. Not sure how accurate the measurements can be.

All this to say: maybe fresh water isn't circulating well, but I don't know how else to check this! (I was going to go through the raw water side thoroughly first before looking at the fresh water side --I pulled my raw water pump yesterday to have it tested by a pump shop-- but I'd be interested to know ways to check fresh water circulation.)

Sorry for the long-winded post...mirrors my confusion over this whole issue! But, yeah, fresh water circulation...any ideas on testing it?
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Old 11-12-2009, 09:08   #38
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Are you sure the Thermostat is opening? You said you replaced it last year...
I would pop another one in there...that's just me..though..

I see that you changed out the impeller cover plate too...with a replacement part..how good is that seal?
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Old 11-12-2009, 09:18   #39
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Are you sure the Thermostat is opening? You said you replaced it last year...
I would pop another one in there...that's just me..though..

I see that you changed out the impeller cover plate too...with a replacement part..how good is that seal?
You're right --while I'm at it, I may as well change out the thermostat: just to be sure!

I have no idea how well the Speedseal impeller cover plate is sealing (they have a good reputation, but I have heard of someone having a problem with sealing with one). Of course, I didn't save the stock pump cover...was several years ago at this point that I changed it...idiot! So, I popped off the pump yesterday and will have a pump shop test flow. However, I'm finding it very hard to get flow specs on it --it's a Johnson, and I have the model #, but Johnson hasn't returned my call looking for a gpm flow spec. I'm hoping I'll get this number and it'll help eliminate the pump as the problem (or point to it as the problem).

Thanks again for the help!
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Old 11-12-2009, 09:24   #40
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The fresh water cooling in my MD17D 2003 is an "add on kit" which uses a heat exchanger. The raw water instead of running through the block runs through the heat exchanger so it's certainly possible if your system is similar for the RW circuit to be clear, but the fresh water to be clogged and not cooling.

Check to see that there is adequate circulation in the fresh water circuit and no crud or blockage limited flow.

My heat exchanger IS the one linked to below and it needs to be cleaned periodically.
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Old 11-12-2009, 09:31   #41
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Jud,

Yes, take one step at a time, once you get the pump info..one way or the other..and re-install it..or replace it......test......then go to the next step.....doing one thing at a time..is the only way to isolate the problem.

BTW....How did the zinc look in your heat exchanger?
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Old 11-12-2009, 09:38   #42
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If you go to post #23

The link provides the flow rates at various rpms


With regards to the water flow issue, here is a link that will tell you what output you should get from your pump at what RPM.

http://www.johnson-pump.com/JPMarine...010_US_web.pdf

You pump is on Page 36



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You're right --while I'm at it, I may as well change out the thermostat: just to be sure!

I have no idea how well the Speedseal impeller cover plate is sealing (they have a good reputation, but I have heard of someone having a problem with sealing with one). Of course, I didn't save the stock pump cover...was several years ago at this point that I changed it...idiot! So, I popped off the pump yesterday and will have a pump shop test flow. However, I'm finding it very hard to get flow specs on it --it's a Johnson, and I have the model #, but Johnson hasn't returned my call looking for a gpm flow spec. I'm hoping I'll get this number and it'll help eliminate the pump as the problem (or point to it as the problem).

Thanks again for the help!
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Old 11-12-2009, 09:44   #43
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Jud,

Yes, take one step at a time, once you get the pump info..one way or the other..and re-install it..or replace it......test......then go to the next step.....doing one thing at a time..is the only way to isolate the problem.

BTW....How did the zinc look in your heat exchanger?
Latest info --I heard back from Johnson Pumps finally and have output specs on my impeller pump --oddly enough, the pump is designed to put out LESS water at max. RMPs than lower down! I had tested my engine flow at max. RPMs, and compared it to a similarly sized engine (which was specced for 7 gpm; I had 4.5 gpm, so tentatively concluded it was low.

Anyway, says Johnson, my pump puts out roughly:
@1000 RPMs: 5 gpm
@2500 RPMs: 10 gpm
@3200 RPMs: 5-6 gpm

So...it looks like the pump, being old, might not be as efficient as it once was...and it looks like I should test raw water ouput at a lower RPM, i.e., around normal operating RPMs, like 2400/2500 --b/c that's where the cooling is important (and should be max. flow). I'm going to have it tested by a shop, to be sure...they only do pumps!

Re: heat exchanger zinc..I don't appear to have one, according to the exploded diagram of the heatex: heatex.jpg (image)
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Old 11-12-2009, 09:45   #44
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Check for obstructions in the thruhull fitting. Barnacles and marine growth can restrict the water flow. I finally used an ice pick to break up the obstruction between the external strainer on the hull, and the thruhull valve. Some of the strainers are designed so that its next to impossible to clean the interior of the thruhull.
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Old 11-12-2009, 09:50   #45
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Jud......someone is blowing smoke....page 38 gives the outputs at various rpms

http://www.johnson-pump.com/JPMarine...010_US_web.pdf
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