new owner with questions

Post here if you want to discuss a topic specific to the MV/32, MV/34, and MV/41.
nocall
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Joined: Wed Aug 01, 2012 10:39 pm

Re: new owner with questions

Post by nocall »

Spent the day trying to get the bottom of the overheating port engine. First I check the oil cooler for lost impeller blades and find it totally clean. Check out the thermostat and it too tests out normally. On a whim, I clamped off a hose to the water heater thinking maybe the possible lower resistance of the water heater circuit might be a path that allowed coolant to bypass the engine and heat exchangers. On the test run it did seem that the overheating was slower to occur but the temp did rise and eventually caused me to slow back down. Finally, after reading on the forum of others who had main heat exchanger issues with sticky insulating goo on the tubes, I managed to pull the core from the HE on the port engine and sure enough, there was a sticky black substance that you could feel. The core will go off to a radiator shop on Monday for a through cleaning and then we will see if it helps. Can anyone tell me what process or chemicals were used to "boil out" the HE's on those so affected? I am thinking heat plus some sort of detergent or solvent but I would like to be sure. The adventure continues...
duetto
admiral
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Joined: Wed Jun 15, 2005 11:18 am
Location: ICW (32043)

Re: new owner with questions

Post by duetto »

generally radiator shops use a well deluted muriatic acid.
john & diane cummings
duetto mv34 #23
nocall
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Posts: 31
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Re: new owner with questions

Post by nocall »

Due to "environmental regulations", finding a radiator shop that will boil out the heat exchanger has been an adventure. Every one I talked to said "we don't do that anymore". Great. I finally found a shop that has a heated ultrasound parts cleaning tank and the HE core has been in the tank for the last 24 hours. With luck, it will be pristine by tomorrow and I can pick it up. With even more luck, I will have the engine back together over the weekend with no leftover parts and it will not overheat.
nocall
1st mate
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Posts: 31
Joined: Wed Aug 01, 2012 10:39 pm

Re: new owner with questions

Post by nocall »

Success! After approximately 24 hours in a heated ultrasonic parts cleaner, the core of the port engine heat exchanger looked brand new. After reinstallation, the overheating issue was solved. Now, if it will just stay resolved life will be good.

On a different subject, what are owners of 75 hp MV34's obtaining for max RPM's under load? On my test run (with six people aboard) I could only get a shade over 3400. The boat had the original 3 blade props replaced with 4-blade props sometime in the past. I will have to search for the size and pitch in the ship's paperwork.
duetto
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Joined: Wed Jun 15, 2005 11:18 am
Location: ICW (32043)

Re: new owner with questions

Post by duetto »

hi,

great news on the overheating!

on to propellers. as far as i know pdq production boats were shipped with 3 blade 16x15 props. when we got duetto it could not pull max revs with full load. our local prop shop told me to get to 3800+ under full load we'd have to de-pitch to 16x13. we did that and for the last 6 years have been able to get 3800 with 90% load. going to 13" pitch had a couple of downsides. 13 knot cruise became 3350 rpm with a heavy load. the "window" to get on plane went to around 3000 rpm. lastly the boat became much more sensitive to clean LIGHTLY painted props. before last year we had let 3 part petit running gear paint build up. last fall i changed shaft seals and while i was at it had props cleaned and balanced. i then sprayed them with 2 coats of petit barnicle barrier. results were amazing. even my wife noticed the dramatic increase in push. hope this helps.
john & diane cummings
duetto mv34 #23
nocall
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Joined: Wed Aug 01, 2012 10:39 pm

Re: new owner with questions

Post by nocall »

I checked and the four-blade props are 16x13, which is one inch less pitch than the three-blade props they replaced. I will work on everything else which might affect WOT RPM's before re-pitching the props.
duetto
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Joined: Wed Jun 15, 2005 11:18 am
Location: ICW (32043)

Re: new owner with questions

Post by duetto »

did you notice the speed you were getting when the rpms maxed out? full load wot gets us a little over 16 knots.
john & diane cummings
duetto mv34 #23
nocall
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Posts: 31
Joined: Wed Aug 01, 2012 10:39 pm

Re: new owner with questions

Post by nocall »

I looked at the sea survey and the engine turned 3600 and was making 16.1 knots. Now that was with a fairly light boat but we did have 6 people aboard. While I don't think I have any bottom or prop fouling, it could be possible. I will be taking the boat out this weekend and will take notes.
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