10m mid cabin - Crusader 8.1's initial impression

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BobCT
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10m mid cabin - Crusader 8.1's initial impression

Post by BobCT »

Finally, it's been 20 months since I picked up the used 8.1's. I'll fill in the gaps, lots of details I can add if anyone else does the same. My first impression is, wow. In all the research I did, there were a bunch of posts and some/a lot sounded unbelievable. Along the lines of, "my new cruise speed was my old WOT", etc. The good news for me is I have 10+ years of video showing my Floscan fuel burn, speed and RPM's. That was the missing piece, I didn't come across any hard before/after evidence and not a 10m repower (of any model) that went from 454's to 8.1's to be found. With all that, the early numbers are pretty impressive. Some random, video comparisons:

8.1's:

3,100 RPM's, 21k, 32 GPH
3,600 RPM's, 24.2k, 40 GPH (this could easily be my new cruise speed, WOT should be 5,000 RPM's, need to break in first to find out)
2,700 RPM's, 17.2k, 22 GPH


454's

2,800 RPM's, 15k, 28 GPH
3,000 RPM's, 17.1k, 34 GPH (this was typically right around my old cruise speed)

At some point, I'll put together a spreadsheet with all before/after numbers for archival purposes. Of course, it wouldn't be fun without some start up issues! In random order:

1) Low pressure oil light. I added the round/four gauge Crusader cluster for each engine which monitors oil pressure, trans temp, CEL and I believe oil temp. The pressure light is redundant to the gauge and I chalked this up to a bad switch which apparently is a pretty common failure. I have a new one coming today. I was about 5 miles out when it came on. Stopped, checked the oil and listened and told myself that I just had to trust the gauge which was perfect. Exactly the warning light you want to see on the first run after a full rebuild! Life is great in that way.

2) Temp gauge on Stb engine, no big deal

3) oil leak/drip on each engine in the pan area. This was a struggle at home with repeated oil pan gasket leaks which I determined was actually the rear main cap on one engine. They sat all winter and not a drop from either. I need to dig into this further. If it's the same issue, I'll just live with it, I'm not pulling them anytime soon and not sure what I would do differently anyway.

4) Maybe most concerning is my oil consumption. I'm about 3.5hrs into my break in period of 10 and then oil change. I've been varying the throttle and the idle/throttle up and pull is great overall. Both engines have used about 1/2 QT of oil over that 3.5 hrs. That's not a crazy amount but, because of issue #3 above, I think I've collectively done more idling over the past 18 months than recommended. Unfortunately, where I store the boat is about 4 miles out to open water in a no wake zone. I pulled a plug on each engine and checked the cylinders with my borescope. I don't see the dreaded "glazed' look that I see in pics online but there is definitely some oil on the top of the pistons and a little on the plugs. I think on my next run, I'll do that 4 miles on one engine and alternate which will get the RPM's up.

For you guys that have broken in new/rebuilt engines, would you be a little more aggressive for the rest of the break in period? 3,600 RPM's has been my max RPM so far. I think the cylinder walls look great, I can still see the cross hatching and no shiny spots which I'm happy about.

More to follow!


Bob
1988 10m mid cabin

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Re: 10m mid cabin - Crusader 8.1's initial impression

Post by prowlersfish »

Engine break in :D . Lot of schools of thought on that . 1) Baby them. 2) Run them like you normally would. 3) Run them like you stole it :shock: . 4) My way . If cam is new and flat tappet, 2000 rpm for 20 minutes. Look it all over and untie the lines . Clear the no fun (wake) zone , bring her up on plane . Vary the rpm and don't baby it doing so helps breaks in the rings. I also do the no no and do a WOT to see if all ok and gets full rpm .
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Re: 10m mid cabin - Crusader 8.1's initial impression

Post by RWS »

Hiya Bob,

Your numbers are impressive.

Did you do anything different with the props?

Does she feel much different in terms of lift and running angle?

Is more of her ass out of the water when on plane?

I'd bet once you get all your data together after break in and graph it as I did your sweet spot for range will be impressive.

Back in 2005 I came close to pulling the trigger on these engines, however due to the length of the shaft in the Express, I was told that I needed to upgrade my shafts to Aquamet 22's, which led me down the rabbithole of diesels.

At the time my own research showed that the 8.1 was both far more powerful AND economical than the 454 (7.4) and way more reliable than a 502.

I am excited for you and your results!

BEST !

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Re: 10m mid cabin - Crusader 8.1's initial impression

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I was wondering about the props also.
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Re: 10m mid cabin - Crusader 8.1's initial impression

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Thanks guys. Yes, on the props I went from 17x14 (four blade, light cup) to 18x21 four blades, no cup. That makes my prop tip to hull clearance on the low end of the recommended range, I’m around 12%. Proactively, I put some acoustic (some type of rubbery fiberboard) tile epoxied to the hull right over where the prop tip is closest to the hull. I read that the prop tip can cause a resonance which feels like a vibration but isn’t actually one in the traditional sense. I do feel a vibration and hoping that’s because I need a final alignment now that it’s in the water. I did one on the hard and then the run above was a splash and go.

The props are still the $1m question. It feels great so far but I’ve only been to 3,600. These 8.1 HO’s are supposed to hit 5,000. I re-used my 1.25” shafts which are aquamet 22 and had them checked while they were out. More than one place said they were fine for this type of boat (i.e., ski boat of similar application not a good idea). My intakes, seacocks also stayed at the original 1.25” hose size. My fuel line from the tank to Racor is the same 3/8” which I had with the 454’s. Out of the Racor to the fuel pump is 1/2” because I had to change it anyway. Crusader specs 1/2” all around but I can’t imagine the Racor bowl running out of fuel, and if anything, the 8.1’s should be burning less right up to WOT than the 454’s. If I hit a wall, I’ll upgrade the 3/8” runs.

How did she feel? The running angle is about the same I would say. I still had tabs all the way down which is how I ran with the old engines. Those were upgraded 12”x24” with added drop fins and always fully down under way. The conditions weren’t great on this initial run plus the distraction factor was through the roof so I didn’t spend much time playing with the tabs. Maybe I can bring them up a hair and pick up even more speed. I did wind up shifting a few hundred pounds towards the stern due to the new transmissions being shorter (and wanting to use the same shafts). So, I could maybe/possibly use some weight up towards the bow. I can fool around with that once I get through this initial phase.

I did feel like it might have been listing towards the Stb side a bit. In the 12 years I’ve owned the boat, it’s always been dead level side to side. Except for my last run before I hauled out and noticed a broken trim tab pin which I replaced. Weird coincidence that it sort of feels similar but both pins are fine. When I upgraded the tabs, I didn’t add an extra piston. Due to the higher speed, are the tabs possibly being pushed back up slightly? I don’t know if that’s possible but worth a look.
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Re: 10m mid cabin - Crusader 8.1's initial impression

Post by prowlersfish »

What's your gear ratio now? My props are also closer to the hull ( when from 20x20 to 22x22 ) no issues
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Re: 10m mid cabin - Crusader 8.1's initial impression

Post by BobCT »

Gear ratio is now 2:1, Hurth 8 degree down angle transmissions. It was 1.52:1 on the old engines.
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Re: 10m mid cabin - Crusader 8.1's initial impression

Post by RWS »

regarding the fuel lines, as I recall the 454 quadrajets had no return fuel line to the tank.

If that's the same for the 8.1's I would think you are OK

If there are return lines, it might be different.

FWIW, after my own repower the tabs have no effect on cruise performance whatsoever, other than changing the angle of the boat.

I suspect this is due to the combined increase in torque & lift.

Your tabs may not be needed as much as before - that said, your weight center is farther aft than the Express with the engines and genny placed as they are.

We'll be watching this thread for more results.

I AM VERY HAPPY FOR YOU !!!

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Re: 10m mid cabin - Crusader 8.1's initial impression

Post by WayWeGo »

Congrats on a nice repower! That's a very impressive reduction in fuel use at 17k, dropping 35%.

I wonder what your sweet spot in mpg is going to end up as once you have everything sorted out, as well as your new top speed.
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Re: 10m mid cabin - Crusader 8.1's initial impression

Post by prowlersfish »

WayWeGo wrote:
Fri Apr 30, 2021 12:48 pm
Congrats on a nice repower! That's a very impressive reduction in fuel use at 17k, dropping 35%.

I wonder what your sweet spot in mpg is going to end up as once you have everything sorted out, as well as your new top speed.
I know someone else that needs a set
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Re: 10m mid cabin - Crusader 8.1's initial impression

Post by BobCT »

port 8.1 10m mid cabin.jpg
port 8.1 10m mid cabin.jpg (63.41 KiB) Viewed 2166 times
8.1_cyl after 3.5 hours of break in.JPG
8.1_cyl after 3.5 hours of break in.JPG (75.26 KiB) Viewed 2166 times

Here are a couple of pics. The top one just showing the portside installed. The 8.1's are a perfect fit from a mounting perspective with two exceptions.

1) The original engine mounting brackets were at an angle for the old 454's. With the 8.1's and a down angle transmission, they need to be level. Once removed, I upgraded the size and thickness of the galvanized backing plates (what mounts each bracket to the stringer) and was able to inject thinned epoxy into each bolt hole. I also added a 1/2" aluminum "shim" the size of the bracket on one side of each engine. I did that because the factory setup was a little wide and exceeded the Crusader spec for the trunnion overhang. On my port side in particular, there wasn't much of the trunnion extending into the mount so this tightened it up and within spec.

2) Figuring out where the brackets should be was a huge challenge, this was like building a boat from scratch in some ways. The engine and transmission were going to be at a different angle and location front to back. How do you figure that out? I toyed with the idea of getting a plastic engine block which I would have done but they're $1,000+ and something I would literally use once. Someone should come up with a rental for these, I'm sure guys restoring cars would rent them all day long. I was at a loss and then had an epiphany after about 4 Coronas staring into the bilge.

How about remove the transmission and bring it to the boat? They only weight about 100 lbs (aluminum case) so this was feasible. I'll let the transmission dictate where the engine should wind up. I should add that I had a bushing made which kept the shaft perfectly centered in the shaft log the whole time. So, that point is fixed - good. Now, get the transmission coupler and shaft coupler eyeball close and let the engine fall where it wants to. I knew it wouldn't be perfect so I made a bunch of mount shims of varying thickness. My goal was to get the mounts roughly at the 1/2 point and THEN start the alignment. Getting the transmission into place was painstaking.

What I wound up doing was using blocks of wood under the transmission to determine where the mounting brackets should be on the stringer. I tacked the brackets into the stringer with sheetrock screws and moved up/down back and forth probably 40 times. Once I got those two couplers basically facing each other, verified that the trans wasn't bottomed out on the hull, etc., then I made the install of the brackets permanent (level side to side across and front to back). Once I was positive that the transmission would line up, I new the engine would as well. The transmission is the low point to the hull so the engine oil pan clearance was a non issue. One unexpected plus, I can now stand in front of the engines for any maintenance. The crank mounted pumps will be nice. The Sherwood E35's are a PIA on the 454's, both changing the impellors and adjusting the belts.

Finally, that second pic is one of the cylinders after 3.5 hours of break in running. Definitely showing some signs of oil but I'm reading that's actually a good thing that the break in is taking place. The cylinders walls don't look like there is any glazing which apparently there is no undoing if that happens.


Bob
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Re: 10m mid cabin - Crusader 8.1's initial impression

Post by RWS »

Bob,

Having that bushing made forcing the shaft to be centered in the shaft log - - - then working forward is simply BRILLIANT !

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Survived Andrew Cat 5, Direct Eye of both Charley Cat 4, & Irma Cat 2
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Re: 10m mid cabin - Crusader 8.1's initial impression

Post by BobCT »

Ha, thanks! It was a huge help in keeping everything on target.
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Re: 10m mid cabin - Crusader 8.1's initial impression

Post by zedtwentyate »

Brilliant job Bob!!!!
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1989 Trojan 10 Meter Mid Cabin

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Re: 10m mid cabin - Crusader 8.1's initial impression

Post by BobCT »

Kegan, thanks. I'll keep updating this thread. Correction on props. New ones are 18x20 (not 21). Michigan Wheel, nibral DQX.
1988 10m mid cabin

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