Cost to replace a 135 hp Perkins?

I’m looking at a very nice Monk 36 with an engine at 7000 hours. It may be just fine but I’d like to know worse case. I see there are rebuild kits, also re-manufactured engines as well.
Also, my experiences with old engines ( non diesel) is they don’t up and die but wear out, get sloppy and the performance drops accordingly. Your thoughts.

7000 hours is a a lot, but maybe half life. In auto terms, a car with 100k miles assuming decent maintenance. Guessing main seals will start weeping at some point but only a guess. Not a known weak spot.

As far as full replacement 6.354, TAD diesel in Virginia is a good source, though you will need to remove/replace. Looks like you're in Vermont. Wouldn't be an awful drive if you have a pickup truck. TAD is also a good source for Perkins parts

https://www.tadiesels.com/perkins-63544.html

Good luck

Peter

If you ever have to replace the Perkins, and I suspect you never will, consider a remanned Cummins 6BT 210 hp. Newer Monk 36s were built with these.

David

Thanks for the inputs, so what might life expectations be for a well maintained Perkins?

15 to 20K hours? Depends on how it has been run and maintained.

Blues said:

Thanks for the inputs, so what might life expectations be for a well maintained Perkins?

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These old diesels don't die, they have to be killed. Salt water into exhaust manifold of broken raw water pump overheats without operator noticing.

But for pure refreshing of a worn motor with no other symptoms, I'd be surprised if it needed a rebuild before 12k hours, with 15k more likely. That said, many parts will be replaced along the way as maintenance items. Exhaust elbow replacement a couple times. Exhaust manifold once. All pumps at least once. Injection pump service once. Transmission is more fragile than the engine - may need a rebuild once. Injectors too.

It's a tough call not just on Perkins, but any engine. Very few recreational users wear out an engine. 9 out of 10 replacement engines are for other reasons.

I'd guess you can get a reman engine and gear for around $12k-$15k. Probably $3k to have it professionally installed.

If the boat is clean and engine checks out, very unlikely you will put more than a couple thousand hours. Even that is a stretch. However, as you can tell by your concern, resale will be a problem so you are right to seek a credit as you will give it back when you sell. Even then, getting people to look at a boat with 7000 hours could be hard. Most knowledgeable people on this list would sooner look at an older boat with 7000 hours in good shape than one with 700 hours because low usage is often a sign of neglect.

Peter

If you are really concerned about the remaining life of the engine, contact Ski in NC a TF member by a PM. Offer to fly him up to the boat, and bring all of the necessary tools to do a blow by test. If the test and overall look and feel checks out including oil pressure, overheating, cold start, etc., you won't have anything to worry about during your ownership. If you have to sell it within a few years, his test should be meaningful to a sophisticated buyer and you probably will get more in increased resale value than the cost of his work.

David

The path of least resistance is a quality rebuilt with like kind Perkins. Your not going to put a Cummins in place of the Perkins at twice the cost. Trans, exhaust hose, shaft, mounts, harness, control panel, gauges, and propeller are all somewhat different too. At 7000 hours you have lots of life left on the engine itself. It’s the bolt-on marinization bits that give trouble at higher hours. With a quality rebuild those bits are new or also rebuilt. Not to mention scope growth items “While you’re in there…”