The mystery of a proper prop and terrible performance.

Discussion in 'Props' started by missinginaction, Jan 25, 2020.

  1. missinginaction
    Joined: Aug 2007
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    missinginaction Senior Member

    Productive day..... I started here....

    IMG_20210617_090951337.jpg

    Started measuring and cutting and installing the Gates Green Stripe hose that I picked up this morning. Once everything was clamped up it was time for another more careful attempt. I started her up and let her run for two minutes. Shut her down and opened the filters and filled them with water. I did this again twice more, she took less water each time and by the third time very little.

    So I started her again and let her idle for about 20 minutes. No problems this time. I used one of those hand held temperature guns to keep an eye on things. Manifolds get to between 170* and 220*, 220* in the centers and lower on the ends. None of the engine coolant hose registered over about 150*.

    One thing I did notice was that the port side manifold was always about 20* hotter than the starboard. Not a big deal but I'm wondering why.

    After she cooled off a bit I opened up the filters and found some interesting debris.

    IMG_20210617_120730466.jpg

    I was surprised at the amount of scale that was trapped after just a short time idling. The filters seem to have been a good idea.

    She warmed to 160* and stayed there but this was just at idle.

    That's it for now. Next steps are getting Pearl cleaned up and into the water. This should happen late next week. We'll see how she does when I can open her up.

    MIA
     
  2. 7228sedan
    Joined: Nov 2009
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    7228sedan Senior Member

    MIA, checking in... How's she running?
     
  3. missinginaction
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    missinginaction Senior Member

    Just having some lunch and was checking in. Well, she's running fine but still in the yard. The cooling system seems to have worked out fine. The Sherwood pump is rated at 35 gallons+ per minute but of course the garden hose that I use to do my test runs/air purging in the yard won't flow close to that. She warms up fine at idle to maybe 1000 RPM and settles down right at 160* or a little better once I got most of the air out of the system. I still seem to have a hot spot in the starboard manifold that runs about 40* hotter than the port side but I'm thinking that once I can open her up there may be some air in there that I've yet to purge.

    Weather has been either blistering heat and humidity or rain and thunderstorms. So I've been taking my time and cleaning her up, bottom paint and working on my rotating dinghy lift. The dink is out in the garage for a final sanding before the finish coats go on.

    If the weather cooperates she's to be dropped in on Friday. If not we'll keep pushing back day by day. Life gets in the way again next week as I have a funeral to attend in Boston. Hopefully she'll be at the dock by then.

    I'll give her some short easy runs, re-torque/check fasteners and then take her down river a bit and open her up. The engineering part of my brain tells me that everything will be fine. Even so I get feeling a little stressed leading up to launch day.

    Thank for asking 7228! BTW, how's your boat search coming along?

    Regards,

    MIA
     
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  4. 7228sedan
    Joined: Nov 2009
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    7228sedan Senior Member

    sounds like a plan! Can't wait to hear the results with that prop.

    My search has been stalled by the Mrs. requesting a back yard make over and swimming pool...

    So I'm ever looking, however the wait will have to continue :)

    Keep us posted!
     
  5. missinginaction
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    missinginaction Senior Member

    The Mrs. is a lucky gal.
     
  6. missinginaction
    Joined: Aug 2007
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    missinginaction Senior Member

    Just an update for 7728 and anyone else who's interested. The National Weather Service tells us that we've experienced 200% to 400% of typical rainfall in our area. Pearl was dropped in last Saturday but just brought around from the well and docked. Far too much debris and current in the river to do any performance trials or testing. It was just a short run at low speed. Nothing unusual.

    So the bad news is the weather which continues to be unusually rainy here. The good news is that this rain really tested my work and the sealants used on the decks and cabin area. She endured a 2" rainfall the other night with no leaks found anywhere. Hat's off to Sika and that 291 LOT that was used to seal everything. It's really done its job.
     
    Last edited: Jul 14, 2021
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  7. Mr Efficiency
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    Mr Efficiency Senior Member

    Might be more a case of thoroughly executed application of that sealant ! Been pretty hot there this summer ?
     
  8. missinginaction
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    missinginaction Senior Member

    Yeah Mr. E, I was pretty generous with the application.

    The weather has been weird this summer here. We go from blistering heat in the 90's to tons of rain as fronts pass through. 90's to 50's and 60's in the course of a day. Haven't had too many days without either heat or rain (or both).

    There are a few guys trying to do epoxy and paint down in the yard and it's driving them crazy. Unless you're in a building it's either too hot or too damp.

    MIA
     
  9. missinginaction
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    missinginaction Senior Member

    Still stuck at the dock. At least I have time to paint the dinghy (CLC Eastport Nesting Pram) at home in the shop. Got a call yesterday from the dock master. "Can you please come down and put some extra lines on your boat?" When I got there I measured a two+ MPH current right at the docks. It's faster out in the channel of course. This is the heart of summer around here and I saw not one boat moving in a 4 hour time span. Why would I? There's nowhere to go (see below). Saw a lot of logs and debris though. We've had worse here but not for this long a period of time, that I can remember anyway. More storms in the forecast for today through tomorrow. In case anyone is planning on using the Erie Canal System here's the latest notice to mariners.....This was from yesterday but nothing has changed as I write this.

    The New York State Canal Corporation today announced the following sections of the Canal system are closed due to the recent heavy rainfall, high flows, and extremely hazardous conditions:

    Erie Canal

    Lock E-2 (Waterford) through E-19 (Frankfort)

    Lock E-24 (Baldwinsville) through E-33 (Henrietta)

    East and West Guard Locks (Rochester)

    Oswego Canal

    Lock O-1 (Phoenix) through Lock O-8 (Oswego)

    Cayuga-Seneca Canal

    Lock CS-1 (Cayuga)

    Updates to follow.
     
  10. missinginaction
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    missinginaction Senior Member

    Finally, FINALLY had a decent day to do some test runs. As some may know this was a pretty big project. Not only was the drive system upgraded but the entire cooling system as well (now full closed cooling) new valve seals (no more looking like a diesel on start up), new intake manifold and new exhaust manifolds.

    So how did it go? Well, three words tell the speed story.

    Not so well. But there is more to it than that.

    We had some minor issues with the new closed cooling system that turned out to be thermostat related. Even though the thermostat in the boat was new, we replaced it and solved the cooling system issue.

    We tested the cooling at 1500, 2000 and then 2500 RPM. Used an infrared thermometer to verify the gauge readings and check around the system for temperature changes as coolant flows in and out of the engine, manifolds and exchanger. Once satisfied I took her up to three thousand and she behaved so I shoved the throttle forward and felt the secondaries open. The bow rose some more but the tachometer stayed right about at 3,000 RPM. Speed measured on the chart plotter was just under 10 knots.

    Then my buddy Bill who was keeping an eye on the engine says "You're not going very fast but wow, that prop is really pushing a hell of a lot of water out back here."

    Reading through this thread there were many who said that trim tabs would probably be needed. Based on what I saw today, they're right. Well, I needed a project for the spring anyway so trim tabs it will be.

    The difference between this new set up and the old one is considerable. The new prop is grabbing much more water. While she still won't get "over the hump", you can feel much more acceleration, up to a point. The old prop and 1.5:1 v-drive gave up at about 7 knots. I never bothered to hold the throttles open with the old prop as she spun past 3000 RPM all she did was make noise and cavitate. The old prop churned a lot of water but the new DQ486 shot water out the back like I'd never seen before. We dug a pretty deep hole. With the old setup she just felt powerless. Now she feels like she want's to go, she's just not quite there yet.

    So for now I'll just take it easy. I'm one for two since the cooling system worked out well. Hopefully after the trim tabs in the spring I'll be two for three. Like the song said, "Two out of three ain't bad.".

    Thanks again to everyone who contributed,

    MIA
     
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  11. Mr Efficiency
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    Mr Efficiency Senior Member

    3000 RPM gave you 10 knots ? That sounds a little worrying. What is the gearbox ratio and prop pitch as it is now ?
     
  12. missinginaction
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    missinginaction Senior Member

    It's all good Mr. E. Read through the thread and you'll see that this is a project boat that I've worked on for some time. The "little under 10 knots" is because the boat will simply not quite come out of the hole and over the hump onto plane. I just replaced the gearbox with a 2.05 to one unit and the prop is a Michigan Wheel DQ486 17 diameter by 18 pitch. I wanted to try her this summer without the tabs to see how she's go. Now I know. She needs a little more lift at the stern. A pair of 24x12 tabs should do the trick.

    Regards,

    MIA
     
  13. Mr Efficiency
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    Mr Efficiency Senior Member

    Yes, I have been following it, just sounded a little too slow to be on the verge of planing. If you'd said 12-13 knots I would be happier for you. Is that 3000 RPM/ 10 knots accurate ? It seems like a lot of slip
     
  14. missinginaction
    Joined: Aug 2007
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    missinginaction Senior Member

    I took my speed reading off of the chart plotter. The tachometer reading is accurate.

    I was in the cabin at the lower helm, my buddy was in the back of the boat. This boat is 25.5' LOA, about 21 at the waterline, 10.5 max beam and 8.33' at the waterline.

    I wanted a "worst case scenario", so I ran with full fuel (60 gallons) full water tanks (30 gallons) most of my tools and supplies on board. She's sitting on her lines but full.

    My helper has been around boats almost as long as I have. He commented on the depth of the hole we were in and the amount of water that was being pumped by the propeller. The bow rose but we just didn't have quite enough thrust to get out of the hole and over the hump. It doesn't feel like slip to me. My old prop was undersized and over geared. She's a planing hull but she's acting like a semi displacement hull. I'm pretty confident that a set of trim tabs will provide the lift necessary to get her over the hump. I'll put them in next spring. For the time being I'm going to let her fuel tanks run down and do another test alone in the boat. If I take the better part of 500 lbs. out of the back of the boat (my friend plus the lower fuel load) she may do better. Lightening the load by 500 lbs. would be about 7% of her displacement.

    We'll see!

    MIA
     

  15. cracked_ribs
    Joined: Nov 2018
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    cracked_ribs Senior Member

    Trim tabs will help but personally I think you'll need less pitch.

    At 20% slip 3000rpm on an 18 pitch prop would put you at around 18.5 knots, that's pretty optimistic for a little engine in a big boat!

    You pitch down to 16, you could probably hit 20 knots at 3500 and I think with tabs and a light load that might be possible. You might be able to flog it on to plane with just tabs and no other changes if you have plenty of space and you're not bucking wind or waves, though. Worth a try because you'll want the tabs regardless, anyway.
     
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