Diesel Conversion...

paulcap

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Hey everyone...I just joined...I`m knee deep in boat conversion for more serious fishing...Striper fishing is the extint but in the onstart of rigging boat for more offshore work...I put a gm 5.7 remanufactured long block in last spring with a fast fuel injection,msd ignition etc. but already wanting a diesel...I have a few buddies at a marine diesel outfit..I`m thinking have them keep eyes open for a great deal on a great candidate for rebuild...I could fix her up while I`m up and running and absorb the cost in a slower manor. Probably need a new gear as well. I`ll post some pics soon...luhrs 30..prelude of the mainship pilot 30. I would lose my wet exhaust and go to stack and glass exhaust holes up un stern. no worries backing down....I want more power and torque....any enging ideas?
Paul,

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paulcap

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From what I`m reading cummins has a great power to weight ratio going for them.....
 

F/V First Team

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A recon Cummins straight from the factory might be the right set up for you. 5.9 or something along those lines. No reason to lose your wet exhaust either, just split the outlet and plumb it up to what you have existing.
 

Robert M

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Steyr seem to be getting popular for a gas replacement. All I know is they are heck of a lot less money. Sure someone will school you.
If your going to drop a cummins in which would be ideal, it may take a very long time to see the $ return. although if boat is in the sentence, $ return is an oxymoron .
 

captainlarry84

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I would find a nice Yanmar 315 HP @ 3800 LP Series. This motor has the same foot print & weigh of your 5.7. I would not dry stack the vessel. She is a Luhrs and you will ruin any hopes of a resale value with a dry stack exhaust. Lastly your current gear, if the ratio is correct can also be used. You need to know what your max wheel diameter & current shaft sizes are.
 

paulcap

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Thanks for the replies guys....granted its a boat but had a couple headaches with the gas 5.7with less than 100 hrs. I ingested water in the cylinder of last engine. That's why a lil paranoid of wet exhaust. Had ran in some steep 6-7 footers that trip...
 

BillD

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Thanks for the replies guys....granted its a boat but had a couple headaches with the gas 5.7with less than 100 hrs. I ingested water in the cylinder of last engine. That's why a lil paranoid of wet exhaust. Had ran in some steep 6-7 footers that trip...

Paul,

No need to be paranoid about a wet exhaust, the vast majority of boats have wet exhausts.

The question you need to answer is "why did your V8 engine" ingest exhaust water"

Was it due to a rotten mixer/riser on the engine or did you have water back up into the engine from the exhaust pipe/plumbing.

You may have to re-design the exhaust on the engine/boat.

Let's start with "what happened" to your motor and figure out "why"

FWIW, Bill D
 

captainlarry84

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Ingestion

Many gas motors ingest fuel do to stretched timing chains & a low exhaust system. At idle speeds with slack in the chain, it allows both valves to stay open during intake & exhaust strokes. Once off idle with the chain pulled tight it does not happen. This factor pulls water up the exhaust & into the cylinders at low speed. Over a long period of time it takes its toll on the cylinder walls. At cruising speed the odds of ingesting water withy a full exhaust push is very slim to none.
Lastly if you plan on a repower cover yourself well and add a surge tube to the exhaust
 

paulcap

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Ah...I see...can never stop learning with this stuff...you guys are a wealth of knowledge! Thanks...
 

John 40

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A friend has a 30 alura, not sure if its the same hull. He converted from gas also with a 240 h.p. Yanmar. I think his cruise is 18 knots and has said boat gets a little squerelly at higher speeds.
 

paulcap

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that sounds like Rob....I`m gunna run the crap out of this repower but will go diesel next go around....I added trim tabs with helped a bit...
 
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