Rebuild or Repower?

[Kevin84]

A boat I'm considering buy (a Tayana 37) has an older Yanmar 3HMF installed in her. According to the owner, the engine runs, but it is not developing its full power. Here's my question. This engine is pretty lightweight for a boat this heavy. Only 30hp for 22,500#. Would I be better off rebuilding the engine (if that's what she needs) or just pulling the engine and repowering with a Yanmar 4JH5E (the engine the TY37 comes with now). A rebuild kit for the 3HMF runs a little under 2300 USD. While repowering with a new engine and transmission will run me between 14-17,000 USD not including labor. Does anyone have any experience using such a small engine in this boat?

[Target9000]

Do you know why the engine isn't developing full power?

[Kevin84]

No, not yet. I'm going down to see her in a few days. Will most likely hire a mechanic to check it out and see whats going on with it. It may just need a few minor repairs, or it could need a full rebuild. I'm planning on the worst if I buy her and budgeting to rebuild the engine. Just wondering if it would even be worth it though. The current engine was rebuilt in 2000. But I don't know who did the work or how extensive it was.

[Target9000]

A lot will depend on the condition of the engine overall and the reason for its not developing power. A new motor will be 20-25k if you hire out the work or 15-20k if you do it yourself. That is a lot of dough.

Expect 3k for a rebuild (bare bones), 5k for replacing "incidentals that might be worn", and at least 2k for the mechanic.

If it is "worth it" will depend on a LOT of factors. Like how much on the current motor needs to be rebuilt. When you start rebuilding you'll want to do everything you can while its out and that can get expensive. Also depends on if you're going to have to modify the engine bed, which can suck, or it might be no big deal, etc.

There is just not a simple answer. Sorry, I know that sucks to hear. But it is what it is.

[Kevin84]

Lol. No, its cool. The rebuild kit I saw looked fairly comprehensive. I'll still have to buy new hoses and belts along with maybe one or two other items, but in the end, it will probably still come out cheaper than a repower. The engine that is installed now was the engine that came with the boat when new. So I shouldn't have to rebuild the beds. And since I'm planning on replacing all her through hulls and seacocks, I might as well replace all the lines, right?

[Horror Hotel]

Engines can't be rebuilt endlessly, even if this is actually the first full on rebuild the life is not going to be the same as a new engine. Also shops who do rebuild engines and don't sell new will be apt to tell you rebuilding is a good idea. A good rebuild will cost half as much but last half as long. Either way if you don't do it yourself it will cost a lot more. I don't see a engine trans combo costing any more than 12k plus some odds and ends. The odds and ends will be another 2-3k, I can't see you spending much more than 15k for DIY. It's the labor that gets you but DIY is only for the mechanically inclined. Most yards mark up the engine like everything else, bills grow quick. I just bought a new 3ym30, $9200 w/ shipping, ready to run. Paid the yard $50 to fork it into the pilot house and that was the only marina services I paid for. Besides the 3 nights I spent at their work wall at $48 a day. After that I finished it up at a mooring ball, ordering from defender as needed. Don't be fooled it took lots of hours, any yard that quotes it out at 20 hours will screw you and you'll end up at 60 anyway. I talked to some very respected yards and got all kinds of quotes. The more tech questions I asked the more defensive they got, to the point where some flat out told me to piss off. A week before they were ready to do it. Most just want you to cut the check and not ask how 40hrs became 65hrs. I read somewhere online about a 3ym30 swap that cost 30k, 8k of it was glass stringer work. That guy got screwed super hard and thought it was a legit bill. Be vary careful. Good luck .

[CR38]

30 HP is not really sufficient for a heavy displacement boat like a Tayana 37. Even if it's running strong you may have a challenge to make decent headway in strong winds and current. I would think a 40hp is really the minimum and 50hp would be ideal.

[maine50]

You might want to see what will fit in your available space. The dimensions are usuallty available online. I have a 24k weight boat that had a 33 hp vetus I pulled ou and replaced with 38hp Beta Marine engine. Their 43 and up wouldn't fit. This might help you make a decision. Another alternative is to see what is available in the used market. You might be able to increase HP and still not buy new engine.

[captain58sailin]

I would replace all of the rubber hoses etc... if you are doing a rebuild, cheaping out on the hoses is an accident waiting to happen. Any of the rubber that is still in good condition you can keep as spares, the rest scrap.

[stevec195]

Back to the issue of "not developing full power". Are we sure that the prop is not just over pitched? Number of hours since overhaul and years since overhaul would also be a factor in the re-power decision matrix.

[Kevin84]

Thanks for all the info. The price for a new engine was quoted to me by a Yanmar dealer in Hilton Head, SC. The engine I was quoted for is what the Tayana 37 is delivered with now, so it should fit. I was planning on replacing all hoses anyway. It just makes too much sense not to. I'm not sure if the prop is over pitched or not. It a three bladed Max Prop feathering prop that was overhauled a few years ago. Possible it's over pitched, but not sure. If I decide on a rebuild, it will be primarily short term, just to keep the boat running and usable till I can repower.

Sent from my HTC6500LVW using Cruisers Sailing Forum mobile app

[stevec195]

I have a max prop as well, and at least for the classic model you can only make pitch changes in 2 degree increments. Often if the engine is underpowered for the boat-as in your case, the operator will opt to place the pitch on the high side so as to not be running at such a high rpm to get out of their own way. This will place an undue amount of thermal and mechanical stress on the engine IF you run the motor at wide open throttle for prolonged periods, but otherwise is not harmful. Sounds like your plan to continue operating for a while is the way I would go as well.

[stevec195]

Also, look into the Beta Marine product. They have great customer services and the parts for the engine itself are all obtained from the Kubota store.

[Rhapsody-NS27]

From what I read, everything seems to be about the engine, but what about the prop? Wouldn't changing to a different propeller help the engine move the boat too?

[a64pilot]

Originally Posted by stevec195

Back to the issue of "not developing full power". Are we sure that the prop is not just over pitched? Number of hours since overhaul and years since overhaul would also be a factor in the re-power decision matrix.

BINGO!
Before you even consider an overhaul, be real sure it's needed. I'd hate to have bought an overhaul when all that was wrong was a partially collapsed fuel line, clogged filter, obstructed exhaust, or it's propped wrong.
Is it hard to start, but the starter spins it really fast, still have lots of blue smoke even after it's warmed up? Have to add oil every time it's run for an hour or more? If not, maybe it doesn't need an overhaul.