Mid cabin - 8.1 install

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BobCT
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Mid cabin - 8.1 install

Post by BobCT »

8D672F3C-85B4-4E35-A352-F6E3DC816946.jpeg
8D672F3C-85B4-4E35-A352-F6E3DC816946.jpeg (118.41 KiB) Viewed 360 times
Well, I’ve been MIA here for a while and finally, have the 8.1’s installed in my 10m mid cabin. What an ordeal, most of which were the engine rebuild(s) oil leak, etc., which I would write a book about when I get time.

They’re in, and I’ll have them running this weekend but unfortunately have to wait until the spring to actually run them and THEN get the correct props. For now, I have a punch list a mile long but chipping away.

The install and fit wasn’t too bad. The mounting brackets had to be relocated (back about 4”) and leveled. In order to figure all of that out, I decided to unbolt a transmission, bring it to the boat and use it as my guide. I started by installing a plastic bushing (had that made) in the shaft log which held it centered. Once that was locked in place, I used pieces of wood and shims under the transmission until the two coupler faces were roughly aligned. Once I had that determined, I was able to find the position of the mounting brackets. Basically, the transmission is dictating where the engine falls. I have the same thickness shims under the front mounts as the rear but will tweak that next.

Some quick highlights:

- my goal was (is) to have the engine mounts to be roughly at the 1/2 way point when the final adjustment is completed. I shot a little low on the mounting brackets knowing that I could shim “up” but not down.

- the best $30 I spent was getting a line drawing of the 8.1 blown up to a 2’x3’ poster and hung up under a hatch. I referred to that constantly as I was figuring out the mounting bracket locations.

- the factory width from mount to mount was closer to the “outside” of the Crusader spec so the trunnion overhang was always too far. To fix that, I added 3/4” aluminum stock behind one side of each bracket which narrowed the gap.

- In terms of overall fit, I had to trim about an 1” off sections on each hatch because they hit the top of the risers. I’m referring to the support sections on the outside edges only so not a big deal. I have about 2-3” of clearance over the aluminum plate on top of each engine.

- I beefed up the factory mounting backing plates in thickness and size. I’m referring to the square galvanized “washers” under the lock nuts. A couple of mine were basically rotted away and all were bowed over time. Fortunately, my stringers were rock solid but I used thinned epoxy to seal all of the bolt holes, then 4000 as I was reinstalling all of the hardware.

- something all mid cabin owners should check is the bonding connections on top of the tank. There are two 8g wires which are designed to dissipate static electricity from the deckplate/hose nozzle. I could tell they were corroded and of course the SS bolts were fused to the aluminum bracket so that was fruitless. I abandoned that location and instead used the section that sticks up on the face of each tank (it looks like they needed this to weld the tank and then it got roughly cut.... I have a pic).

Not only were the connections no good but I had to go back about 3’ on each side until I got to clean wire. On this point, I don’t have confidence that this wiring was doing anything at all. This would be a PIA to repair with the engines installed but possible. My new attachment points now are much more accessible.

I have more pics and will add to this post going forward.

Bob
1988 10m mid cabin

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prowlersfish
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Re: Mid cabin - 8.1 install

Post by prowlersfish »

Looks good . Did you go with a different transmission ?
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BobCT
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Re: Mid cabin - 8.1 install

Post by BobCT »

Yes, they came with Hurth 8 degree down angle 2:1 units which I’m using. The difference in length (about 5”) pushed the engines aft so I didn’t have to buy new shafts.
Now I can stand in front of the engines which will be great for service.
1988 10m mid cabin

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RWS
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Re: Mid cabin - 8.1 install

Post by RWS »

Hi Bob,

I am happy to see the results of your doing this repower.

Knowing you as I do, it is clear the upgrade will be TOP NOTCH.

As I almost pulled the trigger on this setup myself, I am excited to see your results - should be a real significant fuel burn advantage, increased range AND a far better sweet spot cruise speed.

Should anyone contemplate this setup on the EXPRESS model, her engines are farther forward than the mid-cabin and her shafts are significantly longer.

The factory 1.25" shafts would in that case have to be upgraded to Aquamet 22 material.

I am hopeful you will consider sending me downsized photos and text that I may establish your adventure over at www.trojanboat.com

BEST !

RWS
1983 Trojan International 10 Meter
Twin Yanmar 315 Turbodiesels
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Trojan International Website: http://trojanboat.com/

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BobCT
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Re: Mid cabin - 8.1 install

Post by BobCT »

Will do, happy to share the details. I got the port engine running yesterday, should have Stb running today.
1988 10m mid cabin

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prowlersfish
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Re: Mid cabin - 8.1 install

Post by prowlersfish »

Bob , Are these New or running take outs ? They look new but you said something about rebuild in your first post . What HP are they ? I was thinking they came in 375 and 425hp . Either way I would expect a good improvement on fuel as the newer engines are more efficient .

Looked at a earlier post see they are 425 hp sweet :D
Boating is good for the soul
77/78 TROJAN F36 Conv.
6BTA Cummins diesels
Life is to short for a ugly boat :D

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BobCT
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Re: Mid cabin - 8.1 install

Post by BobCT »

Running take outs but wound up doing a full rebuild. The hours were low, but they weren’t maintained and the cylinders were scored. Yes, the are the 425HP which is really just a higher redline vs. the 385HP versions. There is a different cam but I’m not sure if that translates to higher torque which is really what I’m after.

I have the same flowscan setup as the 454’s so I’ll be able to see exactly what the fuel burn difference is with the 8.1’s.
1988 10m mid cabin

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WayWeGo
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Re: Mid cabin - 8.1 install

Post by WayWeGo »

Looks great -- can't wait to see the performance data!
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