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454 Replace Repower or Rebuild?

L

Lionel2100

New member
First, thank you for the assistance on my other thread. So now I’m at the point where it’s the repair, repower, replace question. Obviously the largest financial decision I’ll have to make other then purchasing the boat. Here is the situation: The boat is an ’85 Silverton aft cabin. The hull is rock solid. I do not wish to ever trade it or sell it, boat stays with me for life and is used as a summer live aboard or (when later retired) long distance coastal cruiser. The starboard 454 is seized and one cylinder is damaged from overheating. This engine has many new components on it and had about 1000 hours. Since I’m going to do this just one time, I would really like some advice from the smart people I keep learning from in these threads.

Choice #1 Bring in a new short block. This is choice #1 only because its what the marina wants to do. I view this as the worst choice, as I will end up spending a ton in labor to get the exact same performance as before. I have about 30 years of boating left in me and if I’m going to keep it that long, I feel if I’m going to sink a lot of $ into it, I should do it all at once when it make sense.

Choice #2 Repower with a new engine. This option appeals to me as the boat is somewhat underpowered. I would like to get more torque and get on a plane easier. WOT with a clean bottom, all laundry aloft and the wind behind me was about 21 knots. The boat was planning at about 15 knots. Unsure of the RPMs were accurate when planning, but it seemed to be over 3000. My concern with this is that I’m no mechanic. I have no idea what will work. My concerns are what will fit under the salon floor, will the new engine mount where the old one was and will the transmission and shaft fit. In short, I view this as an expensive choice, so diesel is out. I would only consider this option if it means a better power plant with minimal additional issues. My fear is that remounting a new engine/transmission would just end up as a fiasco of labor costs as mistakes are made.

Choice #3 Rebuilding the existing engine. Would it be possible completely disassemble the entire block and systematically rebuild and upgrade it? For example, could if I just get the cylinders rebored and new pistons used so that it comes back shiny new and stronger? Also, I read another thread where a 454 had the cam exchanged to give it more torque? And while I’m at it and the head it off, could I have it ported and all the valves checked/replaced? I view this as an attractive option because I feel like I could get a lot better performance, I know it would fit right back where it belongs, and its already got new carb, new starter, new belts, new pumps…..

Your thoughts are appreciated.
 
You talk about repowering the starboard engine and getting something with more umf. What about the port engine? you should try to match them for power and the other question is how many hours are on it. Are you going to have to replace it soon as well. Going with a new engine means all new external parts and possibly going to fuel injection which could be a pluss. The big question is how deep are your pockets and how much are you willing to spend.

I went with the long block out of the cost and have no regrets but going with a completely new engine? I would have if I could have.

Good luck and have a safe 4th.
 
I'm not a bottomless boat pit of cash lol. The port engine runs ok now, but both have over 1000 hours on them. It just occurred to me that I hadn't considered fuel injection. That would make a huge difference but that would also create a lot of cost. I priced them and there is a wide choice, all expensive, but again, I have no clue what to consider as options that would fit in the boat.

Thanks for the reply, have a great weekend!
 
..."Bring in a new short block. This is choice #1 only because its what the marina wants to do."

And they are correct!

Jeff
 
Jeff, why a short block and not the long block? with the long block you get the heads as well. The price is more but all in all you are pretty much complete.
 
What is the access like ? Could a compete engine be removed and installed without disassembly or taking the boat apart ? If not, it limits your options.
 
If your WOT was just over 3000 it sounds like you either were not developing full power in the engines you have (had) or you were over propped. Some research will tell you what performance you should obtain and what props are correct. I would repair to get it running right and then just enjoy it. No boat is perfect. Souping up engines can result in a lot more expense, little more performance, and additional maintenance. Since you intend to keep the boat long term you will find many opportunities to spend money on upgrades that will bring more enjoyment to your boating.
 
..."Jeff, why a short block and not the long block?"

That's what I meant to say. And forget about installing fuel injection. A properly tuned carb equals it for on-plane gas mileage.

Jeff
 
In a perfect world a detailed post mortem on the remains would be performed to determine the cause of the failure and then an informed decision on whether the engine can be rebuilt. The more practical way forward may be to procure a remaned long block of the same vintage and staying with the carbed system. If your other engine is running well and has been maintained, at 1000 hours, it is probably at its half-life. Hang in there and try not to get discouraged.
FL Panhandle
 
With 1000 hours, the heads are due for a refurb (both sides) so if you want the 'missing' torque, you'll likely have to do both sets of heads....

If you really want more 'umf', you need more cubic inches - a rebuilt set of 502's would be ideal....good news is most all of your bolts-on's would fit...just gotta get the correct blocks...

Its really gonna be driven by your budget....if you are serious about keeping it forever, the new option would be more expensive now but give you less headache in the future....
 
Forget the budget. Let's bolt a bracket to the stern and hang 3 300Hp. Outboards on it. Remove the tired engines,the rudders,struts & shafts. Get rid of all that weight and drag. That will add some cubic inches. She'd move then.
 
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