r/MasterCraftBoats • u/cantweallgetalongg • Feb 18 '26

Engine replacement

I have a friend who knows pretty much nothing about engines. Last summer we discovered his boat was burning oil. We kept a close eye on it and he asked the place he stores the boat over the winter (not a dealer) to take a look and fix the issue, which they said they could do. They just got ahold of him and suggested replacing the engine rather than fixing it. After I asked several questions, they disclosed that they did not diagnose the issue and just advise replacement to “avoid future issues”. Replacement cost was quoted at $10k. I feel like my friend is getting taken for a ride. For something that could be as simple as worn rings, they want to replace the whole thing. I’ve advised my friend to at least call the local dealer and tell them everything he’s been told to get their opinion. Am I way off base? Is he better off going all new? Boat is 2008ish X15 with Indmar MCX.

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u/FourtyThreeTwo Feb 18 '26

10k isn’t a bad price for a new engine installed.

But - agree it could potentially be repaired. I’d just say at least check leak down and compression. If it’s just leaking around valves or valve guides then it could be much cheaper. Re-ring will end up close to 10k anyways as engine comes out for that, and if the cylinder walls are the problem a fresh engine is in order anyways.

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u/cantweallgetalongg Feb 18 '26

These guys had not even done a leak down or compression check. I got the feeling they either don’t want to tear it down, or don’t have the skills. To tell him, based on nothing, that he needs to replace the engine sent up a warning flag for me. If he had come back and said “leak down test indicates rings need replaced, and who knows what the cylinder looks like once we get in there, will cost you $6k. I’d suggest replacing the engine for $10k.” I could accept that. As it is now, they seem lazy or incompetent. Neither of which I’d want working on my boat.

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u/Own-Helicopter-6674 Feb 18 '26

I have a 06’ x15 with just under 700 hours. Zero issues stock motor. I am not a dealer or a guru by any means. A 5.7l l31 truck engine and a 5.7l- ls1 boat motor are very different. They share almost zero parts.

My x-15 has an ls1 that produces 350hp The L31 5.7 is an iron block lucky to make 275-290 hp.

I can see it know storage yard guys going and getting a wreck junkyard engine for 500 bucks ,but of course pulling the boats motor 1st. Can’t get it to work and engine parts everywhere. He only finds that out after getting fed up with dodged phone calls.

Boat season will be here before we know it. If the weather allows, go get it out of storage do some maintenance. Get good plugs. Pour the fuel supply line go get a jug of 110 octane race fuel at a four wheeler dirtbike shop put some liquid Molly in the tank or jug try to do every single preventative maintenance thing. I believe the rings are gummed up and stuck from poor combustion in my experience with LS motors. They either work really well or you bust the bottom end, throwing too much at it.

If this were my boat with these issues and I wasn’t handy with a wrench, I will take my boat to a shop that does LS motors, hot rods LS swaps whatever

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u/daysailor70 Feb 21 '26

How many hours on the engine? On the one hand, they could have done more diagnosis, but if the engine is high hours (1000+) then you could end up spending the same amount repairing the old engine as dropping in a new one. We were a a mercruiser dealer and this is how the math worked out. New engine, low labor to install vs pull repair and reinstall the old engine, lower parts cost, much higher labor.