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I am looking at a 1978 31' Flying Bridge Cruiser. At this point I have not dug into the history of the boat enough to know the service history on the engines except that I am told that they are original. I have read some of the posts here about upgrading to diesels so I understand that that is one option. Can someone give me an rough idea of the cost of rebuilding or replacing the original Mercruisers?

Thanks,
Peter

there's a tremendous amount of variability depending on what all has to be done. You could be looking at anywhere from $15k-$50k+ for gassers and the high end of that or quite a bit more for diesels - maybe $75k ballpark if you are hiring someone to do the work?

Cheapest option would be remanufactured gas long blocks and change out "accessories" (alternators, pumps, etc) as needed. There's a lot of labor in that option though so that tends to be most practical if you are doing it yourself or if you have access to relatively inexpensive but reliable/qualified labor (if such a thing exists). The more "accessories" need to be replaced (likely pretty much everything for that old of a mercruiser), the better off you are just getting a new "bobtail" with a warranty. Cheaper route there would be something like a carbureted marine power 454 (see michiganmotorz for general pricing info), nicer/more expensive option would be something like a HO MPI captain's choice (no idea about the fit for a b31 engine room, you'd need to verify all that). Diesels you may have options like a reman cummins, but you'll need to call around for pricing. SBmarine is one place you get get quotes for reman cummins, but i wouldn't bother to call them unless you are willing to spend the coin. And keep in mind that things like shafts, exhaust, etc all need to be addressed for a gas to diesel repower, and they need to be done right.

Thanks for the helpful suggestions. Assuming I went with a turnkey package like the one from Michigan Motorz what could I expect in the way of labor costs to install? I am on Long Island if that makes a difference.

Thanks,
Peter

again it just really depends on your specific situation. Often when someone does something as intrusive as swapping engines they do a lot of other stuff "while they are in there" - like stripping out old wiring and harnesses, painting the bilge, maybe re-doing the mounts, battery trays, etc., etc. Some of it is stuff that you don't know needs to be done until you get in there, some of it is stuff that is kind of "personal preference." Also the specifics matter - if you are going from 454 to 454 with the same cooling and exhaust configuration, that might be less (in terms of labor) than switching to 6.0's for example. Very rough ballpark based on a estimate i got for a different boat is maybe $5-$10k in labor if you are sticking with the same engine type. But, again, it could easily be twice that, or a little less, depending on what else you are doing while you are in there, how good the access is, etc. also trannies are another expense, if needed.

I'm weighing in on this because I've been in your shoes. Since this is a boat you do not own, you have limited ability to really figure out what needs to be done. So if you move forward with it you are going to have to accept that there is a very, very wide range of possible costs with respect to repowering it. And the way things always seem to work, you should have a healthy reserve on hand so you can complete the project if it ends up being more than even the higher end of the range of what you planned for.

The issue is once you pull the engines, what are you looking at. Are the engine supports good? Do stringers need to be replaced, how about the bulkhead aft of the engines. Rudder shelf etc.

These are things we have all faced.

pschauss wrote:Thanks for the helpful suggestions. Assuming I went with a turnkey package like the one from Michigan Motorz what could I expect in the way of labor costs to install? I am on Long Island if that makes a difference.

Thanks,
Peter

Peter.... who used to have 2 31's out in Hampton Bays?

mike ohlstein wrote: Peter.... who used to have 2 31's out in Hampton Bays?

Not me.

Peter

I will add one more thing, If you were just dropping in new engines complete with Transmissions no other work I would have to guess around $30,000 if you pick the 10,000 package and no transmissions. That means touching nothing else. Unfortunately that is not happening. If you don't touch it and have it all done for you including what ever else you run into you could hit $50,000 easy depending on what has already been done to the boat.