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Topics - Denon Osterman

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Jet Pumps / Ride plate tuning / issues
« on: May 30, 2022, 10:33:57 am »
Hey everyone,

I've got a 20' boat, hull dry and without engine is 900 lb, engine is a 550hp (Dyno) big block Chevy with aluminium heads...all in wet weight likely 2000 lbs with me.

SD309 with the performance intake (shoe and plate), AA impeller. Have trim.

Last year when I took the boat out, the ride plate was not installed. The boat ran very happy, but would start to be a bit unstable at very high speeds if I trimmed out. So, I added the ride plate to try and prevent that. Verified angle of 2.7 degrees, which is how it wants to be based on the machined mount.

Now it's not nearly as happy and has a tendency to porpoise at lower speeds, and has a much narrower window of "happy trim" at higher speeds. What gives? I used to be able to hit 60 with confidence, but above that got hairy. Now, 60 is hairy, and even 40 can start smacking the bow if I trim up.

Any help much appreciated!

Engine Mechanical / Electrical / Ignition timing + idle speed
« on: September 18, 2021, 03:47:01 pm »
Hi guys,

So right now timing is 10 degrees initial until 1000 RPM, then I add in 24 mechanical all in by 3000 rpm for 34 total. Runs great, but pretty sure I could have more timing and bring it in faster.

So I swapped springs to the lightest pair (was on second lightest already). No change to the 34 final, but now it's in by 2k, and starts coming in at 500 - which meant my "initial" (timing at idle) is actually closer to ~13-14.

Well, it ran a little better at a slow cruise, but couldn't idle to save it's life. Would hunt like crazy, stall frequently, all sorts of crap. I swapped back to the medium spring and all is well again. Here's my questions:

- I've done a lot of research on timing and I cannot believe that an extra ~3-4 degrees of idle timing, when it's already so low, is causing me to idle so badly. I know a lot of people lock out their timing at ~32-34 right at idle and are mostly fine, lots of people have 15-25 initial, etc. So what gives...why do I need such a ridiculously low initial timing?
- My idle speed is 800 rpm. From everything I've seen on this site, that's *really* low. I love it because it's quiet, makes it possible to dock somewhat easily, etc. Could this be why I need such retarded timing at idle? Is there any downside to idling so low?

Let me know if you need any engine specs (492 chevy, cam is a hydraulic roller ~230 @0.050, 0.600", 112 LSA, installed 4 degrees retarded) or if you've got any thoughts...thanks!

Engine Mechanical / Electrical / New build complete + weird noises?
« on: August 28, 2021, 04:24:12 pm »
Hi all,

Long time lurker and immensely thankful to all the help I've gotten from you folks, even though I'm all the way up in sunny Ontario, Canada! I finally, *finally* got my boat finished and in the water and my god am I in love. Full details below for those that are curious on the engine / hull / pump. I cruise at ~15% throttle or 3k RPM to hit ~35, and so far my highest speed is 60 mph (on GPS) at less than half throttle, low 4000s RPM. Wooo!!! There's only two things stopping me from really pushing it. The first is I stupidly left the ride plate off my pump...and it definitely wants / needs it for stability. The trim / place diverter is so incredibly sensitive right now it's almost laughable...the nozzle is 3' back from the transom and there's nothing for the boat to ride on to balance it. The other thing that's worrying me are a few noises I'm not a huge fan of, that I'm hoping you guys can help me with! Engine is fresh off the dyno (~30 min break in to seat the rings plus a few pulls), pump is "brand new" after sitting for about 6 years, freshly greased with Valvoline front and rear.

  • Noise #1 - Clunking at idle. I've read both on here, and in the American Turbine manual, that this is common at idle when the pump hasn't had a chance to load the impeller. My bowl only sits ~3/4 into the water so I'm hoping this is the case? But if someone can confirm, that would settle my nerves.
  • Noise #2 - an incessant whine. Once on plane and at cruise speeds or higher, there's a whine. It's directly tied to engine / pump speed. It's not aggressive, or angry, or even that loud...but man it gets on your nerves after a while. It sort of sounds like a blower, but quieter, and more muted...and my build is N/A. Any ideas on what this could be, or how to stop it?
  • Noise #3 - a more metallic sound that only comes on higher up in the RPM range, when accelerating. If I give some throttle, say to get from 3700-4000, you hear it. Then if I let off just the slightest touch to drop to's gone. No idea what it could be, and a bit concerned given the metallic nature of it. It's not a grinding or a scraping...sort of hard to describe...but definitely more metallic than the whine.
Any help would be MUCH appreciated...and I've done my best to include pics. Video coming soon, hopefully :)


Modified Glen-L rampage that's longer, wider, and taller than stock. Built with a combination of mahagony and white ash / sitka spruce / white cedar. Hull weight without engine, rigging, etc is ~900 lbs. I estimate ~2000 "wet" and ready to go. The deck is a deeply stained mahagony as well, even though it looks sort of black in the photos.

American Turbine SD-309, AA impeller, performance intake (shoe, ride plate that's not yet installed), and the newest version of their trim system. I also added a custom trim gauge that I made using 3D printing and a bike brake works really well, and I'm happy to share details / files if members are curious.

492 chevy (40 over instead of 30), Scat forged crank and rods, icon forged flat top pistons, AFR 265 heads, a custom hardin / comp cam (226 / .591 intake, 234 / .601 exhaust, 112 LSA, installed 4 degrees retarded), Vic Jr intake, and a Sniper EFI system which I am *LOVING* and also happy to share all of my details on. Exhaust is a Hardin seaward system, water jacketed with the mix point occurring ~2 ft after the manifolds. Thermostatic water (10 AN lines, 4 port thermostat @ 160 degrees) and thermostatic oil (2x16" tube cooler, remote filter, 10 AN lines...running 20W-50 break in but will likely switch to straight 40 or a 5/10/15W-40 as pressures are a titch high with the 20W-50).

If I forgot any pertinent details, don't hesitate to ask!

Engine Mechanical / Electrical / Cam selection / beating a dead horse
« on: October 24, 2018, 11:51:14 am »
I know this topic has been dealt with about 1000 times, but I'm going to toss up some cam specs and see what everyone thinks. Some background:

-Boat is a 20 ft custom built wooden hull - hull on it's own is estimated around 700 lbs. 12 degree Vee.
-Pump is a (brand new) SD-309. It has an AA impeller in it now, but I'm guessing that will be a little bigger than I'd like. I don't mind cutting it down or getting a smaller one.
-Engine is a (rather old, but in amazing condition) Merc 365 Magnum. 454 4-bolt with forged everything, ~9:1, 188 rectangle heads, currently has a high rise dual plane and a 850 Qjet, but I'm likely going to get a Vic Jr and 850 Double Pumper with the new cam.
-Exhaust is Hardin "Seaward" HP500 manifolds and (water jacketed / wet) 4" tailpipes, which I've been assured won't be causing any reversion issues with any of these cams.

I'd like the boat to run on pump gas - 91 is OK - and obviously perform as well as it possibly can. Reliability is pretty important, probably on par with overall power.

Here are the candidates - if they're all completely off base please let me know, I'm by no means set in stone on any of them. Would love to hear everyone's thoughts and opinions. All are hydraulic rollers.

CAM 1:
Intake, 284 adv / 230 @ 0.050, .547"
Exhaust, 290 adv / 236 @ 0.050, .547"
112 LSA

CAM 2:
Intake, 284 adv / 224 @ 0.050, .566"
Exhaust, 284 adv / 224 @ 0.050, .566"
112 LSA

CAM 3:
Intake, 283 adv / 223 @ 0.050, .566"
Exhaust, 290 adv / 230 @ 0.050, .575"
114 LSA

CAM 4:
Intake, 286 adv / 226 @ 0.050, .591"
Exhaust, 294 adv / 234 @ 0.050, .601"
112 LSA

Thanks everyone! Hoping to get the engine fully ready over the winter (I'm in in Canada) so I can launch in the spring. I'm sure I'll have more questions, but figured this would be a good place to start stirring the pot ;)

Engine Mechanical / Electrical / 454/496 build for Glen-L rampage
« on: November 30, 2017, 07:25:59 pm »
Hi everyone,

First time poster here - I've been working on a Glen-L rampage for a few years now and am finally ready to get some iron in it! Apologies if you see this exact same post on similar forums...I'm trying to cover my bases, of course. I have also done some extensive searching on this forum and others to get an idea of everything, but I'd rather get some specific feedback on my application / thoughts before I pull the trigger, if that makes sense.

Some quick background - it's a 20', 1000lb hull, with an SD-309, performance intake (shoe/ride plate), and AA impeller. See below pics on current progress. I'm pretty committed to a 454/496 - I know, I know, a ford or olds will be better to half of you, but I'm a chevy guy and already own chevy mounts / accessories. Lightning water jacketed headers as I can't run twisties on my lake, and I'd like the build to spin my pump at 5k for the next ten years on pump gas without a dead nuts reliable 550 hp is what I'm looking for. Experience wise this is my first V8 build, but not my first engine and as a mechanical engineer by training I should be a pretty quick learner.

Here's what I'm thinking so far:

-454 block, 4 bolt mains, junkyard.
-Eagle or Scat stroker kit - scat only offers a 489 but if they're head and shoulders over eagle I don't mind loosing 7 ci.
-AFR or Brodix aluminium oval port heads, ~275 cc runner volume, with chamber matched to above pistons to get me around 9.5 - 10:1 CR
-Victor Jr or RPM Air Gap intake
-Holley 850 Double Pumper - likely the marine version as it's a wooden boat and I'd rather be safe than sorry, though the engine is definitely sitting loud and proud in the open.

Notably absent of course is my cam choice...I'm pretty dead set on a hydraulic roller and I need to worry about reversion from the wet exhaust (water *jacketed*, not injected, but the water ends up in the pipe down stream anyways)...otherwise I am all ears!

Please tear me to shreds and tell me I'm out to lunch - I'm not here to feel good about myself, I'm here to learn. And of course, if you guys have any questions or want to see more pics, just ask - and otherwise thank you all very much for the help!



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