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dh20

time to move up... engine(s) question

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I'm looking to move from my 256 SSi to a cruiser... probably under 30FT... I was considering a single engine... but after reading many posts about the 285 SSX being under powered with a single 496 Merc... now I'm considering something perhaps a bit smaller... what's the rule of thumb when you should consider having twins... it is tied to weight?, cruising speed?, performance?

I agree with the added value of security and easy of maneuverability with twins... and haven't ruled it out.

This also makes me wonder if moving to a cruiser/trawler with diesel make more sense... perhaps having a hull designed for 8-12 knots that sips fuel is more practical... 

Anything you can share would be great - from personal experiences etc.

thanks

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Well I can tell you one thing when considering twins -- Cost of maintaining them is no fun!  What you do to one you have to do to both.  Seriously though, the size and weight of the boat play a big factor.  More the size than the weight.  You have to have a larger boat to be able to hold two twin Sterndrives in the engine compartment.  But then there is speed as well.  I have twin 5.0's that total 520HP in which your likely not to get with one single sterndrive; even the large 8.1s only gets between 375 and 425 HP.  Then you also have to think about fuel consumption.  Running two twins vice running one your are burning twice the amount of fuel.  Think my next boat is going to be a straight inboard with a one single CAT motor. 

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I went from a single VP 5.7 Gi (~275 HP?) in my 1997 Four Winns Horizon 240 bowrider (24' LOA) to twin VP 5.7 GXi-F in my 2006 Chaparral Signature 330 (35' LOA). I think it's pretty much a given that a 35' cruiser will have twins. It's also pretty much a given that a 24' bowrider will not. That said, singles can be limiting in tight spaces. It's very difficult to back into a slip with a single. I love my twins now, but it is definitely more maintenance and increased fuel burn.

I think for me, the line is around 28' LOA where I would begin looking at twins vs. singles. I also think the style of boat plays a role. Something tall like a cruiser with lots of surface area to catch wind will benefit from twins sooner than something low to the water like a go-fast.

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I have a 1999 2835 which is the 285 now with twins.  I can't imagine having the boat with a single.  With the twins the hole shot is great.  I can take the kids knee boarding and get up on plane just as fast as the kids do.  Yes you have twice the maintenance but it's basically oil changes and impellers.  I haven't had anything major done yet so I'm lucky.  

Fuel consumption is not too bad.  I feel with twin I can run at a lower rpm versus a single to maintain the same speed.  So your not really burning twice the fuel, but you are burning more.  

At 28 feet that is probably where you are on the fence for a single or twin engine boat.  

Good luck.

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724 -- Just oil changes and impellers?  I'm shock your boat is still running.  What about the exhaust manifolds, risers, and having to remove the outdrives for service on the bellows, gimble, etc.  Heck just changing out the gear lube requires the boat to pulled out of the water.  I don't trailer mine so that is a hastle in itself, cause I have to drive it to a Marina that can pull her out, pay those fees, plus lay-up yard fees etc. 

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It does sound like 724's day is coming.. A 20 year old boat that has never had a tune up , bellows , outdrive serviced, alignment etc.. is DUE. 

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We have several different boats of all different sizes, layouts, and intended purposes (which is why we have more than one, as you know every boat is a trade-off).  To me, you start with the size and layout that accomplishes what you want to do with the boat.  Then you decide how fast and/or how much holeshot you need (watersports vs no watersports, getting on plane with your "normal" load of people and gear, etc.).  Those two things alone will probably tell you (a) if the boat you WANT is even offered with the drivetrain you NEED and (b) if you should or must go with twins vs. single.  Then you factor in the "desirables" such as do you want twin engine maneuverability and power vs. additional maintenance, do you want twin engine security, etc.

For us, it has really come down to "If it is 8'6" beam, it's gonna be a single but definitely a big block" and "if it's wider than 8'6" beam, it's going to be twins".  Those two simple rules work for us but won't necessarily work for anyone else, it's very personal and situational.  Also, we love our diesels on our big boat but when they break, man oh man get out your checkbook.  But you simply cannot beat the safety of diesels.

Finally, regarding your "8-12 knot" question, you'd be looking at a fairly large boat.  Our 44' express cruiser will sip gas at its happy hull speed of about 8.5 knots.  Fuel consumption goes way up once over hull speed, and it's nowhere near linear.  To get 12 knots from 8.5, we go from about 6 gph total to about 16 gph.  It's a lot more fuel for a little more speed as you start to push water, as it is with any boat.  The hull speed equation is pretty darn close... 1.3 X the square root of the boat's length at the waterline. 

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I'm sorry....I bought the boat used and I've only had it for eight years now.  The risers and bellows were done then and they are still good.  The bellows and outdrive were done a few years later.  The spark plug, oil change, and impellors I do myself.  

I am due for outdrive service again at the end of the season.  But I don't think I am paying for twice the amount for service just because I have two engines.   Maybe twice for the materials but the labor rate isn't twice as long.  Unless my mechanic isn't billing me correctly. 

 

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Maintenance on twins isn't really twice the cost.  As @Jjlai724says, parts are twice as much, but labor usually isn't.  Once I have tools out and  ready to go, the second repair or maintenance items goes pretty quick.  Some exceptions, but in general two oil changes only take slightly longer than one.  Now when it comes to expensive items like riser and manifolds, yep that hurts a bit more.  I do enjoy the insurance factor of having twins.  Twice in three years I have been happy to come back to the slip on once engine where with a single, I'd have been calling for a tow.  If I were to do it over again, I would go with a Sundancer 310, where you can get twins with all inboard running gear.  No outdrives to worry about.  

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I remember some twin boaters doing a test with 2 engines.  O Bs that equaled max HP.  They raised one engine & cruised on the other. Said it was a big saving on fuel.  True or not ?

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Web search  

www.passagemaker.com  Strategies for long range cruising with twin engines  April 21, 2017

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I can tell everyone that age plays a BIG role in having twins in high winds & currents.  Eyesight.  Hand eye coordination. Speed of brain decision during a gust.  Just a dread of the high afternoon breeze waiting for you.  

I could really use  2 …….9.9 hp electric starting Evinrudes on the 16 ' Lowe 52" beam boat.  It is so light it requires constant throttle / steering during the last left turn into the slip with my neighbors wide boat.  At 81 Most every thing on me still works fine for docking needs...…………………. But I really need twins.  To not tense up almost every day with our 25 mph gusts. 

The 186 SSI & V8 is a wind sensitive beast due to excess power swing of the stern so fast instantly either way.  My Son in law is the only driver I trust On the few days they come up. ALWAYS BUY A TWIN ENGINE.  If you like the boats looks to buy it. Duo Prop ONLY !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!  Life is good   Even  I can dock a Twin Duo Prop in 50' waves.  

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Am I missing something?  Most mechanics charge by the hour and if you need to have your outdrives serviced it's going to take the mechanic twice as long to service them both, so he'll charge you 80-100 an hour for the total amount of time taken to service both outdrives.  724, if you have Risers, Bellows and Manifolds over 8 years old you are running on borrowed time.  Especially if you are operating in Salt Water.  I'd suggest getting those inspected because the last thing you want is to crack a manifold and have water dump into your engine block.  Or those bellows dryrot out on you and fail when far away from the dock.  You will take on water very, very quickly.  Be careful my friend.

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Totally agree .  Same for the rubber shifter cable rubber boot being changed also. Actually anything passing thru the transom below the water line is very suspect.

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I am a little late on this!!! But if it was me and by next year to 18 months I will be moving up. No more out-drives, inboards only. Far less maintenance, but with a bow thuster.  And yes, diesel. A straight shaft/s is far less work than out-drives. But you do give up space.

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7 hours ago, Iggy said:

I am a little late on this!!! But if it was me and by next year to 18 months I will be moving up. No more out-drives, inboards only. Far less maintenance, but with a bow thuster.  And yes, diesel. A straight shaft/s is far less work than out-drives. But you do give up space.

Pros and cons to each. It largely depends on how you use the boat. A large driver for me is having a shallow draft for pulling up to sandbars and bays on Lake St. Clair. Even with outdrives trimmed all the way down, my draft is 33" That's pretty handy for pulling into 4' or less of water.

Besides that, inboards are less maintenance, especially in saltwater. You do give up some performance and fuel efficiency due to the prop shaft angle being static and not being able to trim like an outdrive to achieve props parallel to thrust direction. And as you mentioned, inboards do take up more room in the engine compartment than outdrives.

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9 hours ago, Iggy said:

I am a little late on this!!! But if it was me and by next year to 18 months I will be moving up. No more out-drives, inboards only. Far less maintenance, but with a bow thuster.  And yes, diesel. A straight shaft/s is far less work than out-drives. But you do give up space.

Agree!  That's why my 250 is for sale and I'm looking at Sedan Bridge Cruisers in the 35-38 foot range with inboards.  No more outdrives!  I can't imagine having two outdrives.

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38 minutes ago, rjbergen said:

Pros and cons to each. It largely depends on how you use the boat. A large driver for me is having a shallow draft for pulling up to sandbars and bays on Lake St. Clair. Even with outdrives trimmed all the way down, my draft is 33" That's pretty handy for pulling into 4' or less of water.

Besides that, inboards are less maintenance, especially in saltwater. You do give up some performance and fuel efficiency due to the prop shaft angle being static and not being able to trim like an outdrive to achieve props parallel to thrust direction. And as you mentioned, inboards do take up more room in the engine compartment than outdrives.

There's also the positioning of the engines if you end up with V- drives.  They're backwards from the way ours are facing and they tend to push them quite back to stern to accommodate the V shafts.  I was talking about a Sea Ray I was following the other day and mentioned how high a bowrise it had, only to be told later by another marina Sea Ray owner that was the result of a boat with V-deives and the engines being put so far to stern making it stern heavy hence the heavy bowrise.  And this person has a gorgeous red Sea Ray she fixes things on it herself (don't shoot the messenger, but it makes a lot of sense) lol.  Or maybe he just didn't have it trimmed right and a lot of people were in fact on board in the stern area

Then the direct drives push the engines a bit more forward to COG of the boat.  Not sure there is any adverse effect to that except maybe it has a little affect on any aft berths?  Less room, closer to engines amd loud?

But I do agree with the less maintenance of having outdrives.

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1 hour ago, Hatem said:

There's also the positioning of the engines if you end up with V- drives.  They're backwards from the way ours are facing and they tend to push them quite back to stern to accommodate the V shafts.  I was talking about a Sea Ray I was following the other day and mentioned how high a bowrise it had, only to be told later by another marina Sea Ray owner that was the result of a boat with V-deives and the engines being put so far to stern making it stern heavy hence the heavy bowrise.  And this person has a gorgeous red Sea Ray she fixes things on it herself (don't shoot the messenger, but it makes a lot of sense) lol.  Or maybe he just didn't have it trimmed right and a lot of people were in fact on board in the stern area

Then the direct drives push the engines a bit more forward to COG of the boat.  Not sure there is any adverse effect to that except maybe it has a little affect on any aft berths?  Less room, closer to engines amd loud?

But I do agree with the less maintenance of having outdrives.

I don't know about V-drives pushing engines back.  All outdrives have engines right up against the transom.  On the Sea Ray at our dock that has out drives, there has to be at least 6" more between the transom and engine than on my Sig 300.  Also, V-drives place the transmission towards the center, so should be better weight distribution. Or am I missing something?

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47 minutes ago, Roady68 said:

I don't know about V-drives pushing engines back.  All outdrives have engines right up against the transom.  On the Sea Ray at our dock that has out drives, there has to be at least 6" more between the transom and engine than on my Sig 300.  Also, V-drives place the transmission towards the center, so should be better weight distribution. Or am I missing something?

Nope, at least I'm not aware of you missing anything and interesting that you picked up on how most outdrive engines are pushed back to the transom since she was standing right at my boat and I was going to show her how my 8.1 was kinda all the way to the back and see what exactly she was referring to, but she talks a lot and I would've never gotten outta there.  But I bet it has to do with no transom shield to mount to or other little things like that which reduce that tiny little bit of space we already have.   Now I'm really curious to see what she has in her 35ft Sea Ray.  She mentioned a pair of Mercs so she must know the room (or lack thereof) making that comment.  She's also this "know it all" and frankly I don't have patience listening to them for too long.  Wasn't worth it.  But good point by you. 

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I/O's allow for trim adjustment which makes a difference in top speed, and if applied correctly better economy in similar hulls. A great side by side was my 30' Sea Ray Sundancer (twin 350 io) and my best friends 300 Weekender (twin 350 V-drives)  I was 7 miles per hour faster at WOT, and the helm was much more responsive at speed. His v-drives maneuvered better at the dock, but at 3,000 RPM I was doing 30 mph and he was doing 25.5. That said he burned 11 GPH at 3,000 and I burned 15.5. Of course the Sundancer was a bit heavier.

Another thing to consider is engine loading. A 28' boat with a single 8.1 is working both the engine and drive line much harder than twin 350's. Twin 8.1's will dent your wallet as they will go through 25 gph at cruise. V-drive shaft seals and/or packing is hard to get to as the stuffing box is under the engine, and alignment is a nightmare as you have to get the engine to transfer case and also case to prop shaft perfected. Straight inboards are much easier, but that does come at the price of more weight forward and compromised storage. The Hurth and Borg Warner velvet drive transmissions are bullet proof, and the shaft struts and cutlass bearings last a good long while.  Pluses and minus to all of them, but if you tend to boat in really skinny water, stick with IO's as you don't get a second chance with inboards.  W

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2 hours ago, Roady68 said:

I don't know about V-drives pushing engines back.  All outdrives have engines right up against the transom.  On the Sea Ray at our dock that has out drives, there has to be at least 6" more between the transom and engine than on my Sig 300.  Also, V-drives place the transmission towards the center, so should be better weight distribution. Or am I missing something?

Nope, not on that point.

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