Rebuild or Repower?

[bobconnie]

As a old time diesel Mech, Ive re-bilt many engines. But theres a BIG difference between a re-bild, and an overhaul !! In almost all cases in an overhaul you have a re-ring and a valve job, new rod bearings, maybe a re-bilt or a new oil pump! Where as a re-bild includes all new bearings includeing the cam bearings, boreing or replaceing the cylinders, new pistons ect ! Theres a big difference !! You can do a overhaul in place most times if theres room, but to do a REAL re-bild the engine must be removed and done from top to bottom !! Bewhere some folks overhauls !! LOL Ive found over the years that poor maintainence is the big problem with most marine engines!! Ive seem a blank look on to many owners faces when ya ask em when they last set the valves !! LOL or even changed the oil and filters ! Ive had a couple of my perkins engines run for over 20,000 hours and stil not burn more then a qt between oil changes !! And not LEAK !! Most folks would be ahead of the game if they took a course in engine maintaince course or geta mechnic to spend an hour or two showing them a few things !! Just my 2 cents. Ive seen to many engines come into the shop for re-bilds that sure did not need them !!!

[sailorchic34]

Questions. Does the engine start up easy and idle well. Any smoke at start or idle. If it starts easy, within a few seconds of cranking and does not smoke, it's probably just a clogged discharge elbow. If your getting lots of black smoke at high RPM it could be a fowled prop or a bad injector.

Diesel engine rebuilding is not too hard. Seems even poor blonde sailor chics sometime rebuild diesels. Really only need basic tools and a good engine machine shop to do the machining. The hard part is making the special tool needed to pull the inner crankshaft nut off in front of the timing gear.

What worked for me was for every thing that was removed, all the nuts, washers and bolts for each piece went into individual labeled ziplock baggies. It took me a month start to finish to pull the engine, rebuild it in the cockpit and reinstall it after taking it to and from the machine shop. The machine shop takes about a week as does getting the parts shipped from yanmar.

Here's a link to my summer of discontent: http://www.cruisersforum.com/forums/...ar-107705.html

[Kevin84]

Originally Posted by bobconnie

As a old time diesel Mech, Ive re-bilt many engines. But theres a BIG difference between a re-bild, and an overhaul !! In almost all cases in an overhaul you have a re-ring and a valve job, new rod bearings, maybe a re-bilt or a new oil pump! Where as a re-bild includes all new bearings includeing the cam bearings, boreing or replaceing the cylinders, new pistons ect ! Theres a big difference !! You can do a overhaul in place most times if theres room, but to do a REAL re-bild the engine must be removed and done from top to bottom !! Bewhere some folks overhauls !! LOL Ive found over the years that poor maintainence is the big problem with most marine engines!! Ive seem a blank look on to many owners faces when ya ask em when they last set the valves !! LOL or even changed the oil and filters ! Ive had a couple of my perkins engines run for over 20,000 hours and stil not burn more then a qt between oil changes !! And not LEAK !! Most folks would be ahead of the game if they took a course in engine maintaince course or geta mechnic to spend an hour or two showing them a few things !! Just my 2 cents. Ive seen to many engines come into the shop for re-bilds that sure did not need them !!!

Maybe I should clarify here. I am budgeting for a rebuild as described here. The kit that I've found includes new pistons, rings, valves, etc. For a job like that, I will probably hire it done as all the yards in Charleston charge an arm and a leg for DIY storage. Usually around 1,000 per month for a boat the size of the TY37. So the cost would quickly add up if I was trying to do it myself.

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[CarinaPDX]

It is wise to budget for the worst case, but I really doubt that it will be needed. Right now it is not possible to know what the problem is, but if you do buy then once you get your hands on her it will probably yield quickly to some poking around. It could be fuel starvation from dirty filters or water buildup in water-separating filters or air being drawn into the fuel system, which would be cheap to fix. It could also be that the valves haven't been adjusted (very common) or she could be over-propped, both discussed earlier. These are all far more likely than an engine with fewer than 15 years on it needing a rebuild. Unless there is blue (not black) smoke coming out the back and/or lube oil spraying around in the engine compartment you probably have a serviceable engine. Assume the worst for negotiating - just don't believe it yourself!

Greg

[captain58sailin]

The other posters bring up a very good point. It would be a great idea to go through the trouble shooting process very thoroughly, you may not even need a rebuild or overhaul. So take your time and maybe save some money.

[Kevin84]

Originally Posted by captain58sailin

The other posters bring up a very good point. It would be a great idea to go through the trouble shooting process very thoroughly, you may not even need a rebuild or overhaul. So take your time and maybe save some money.

That's what I'm hoping for. If I can get the engine running strong for a few hundred verses a few thousand, I'll be a happy man.

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[Kevin84]

Ok, found out a little more about what's going on with this engine. She apparently starts and runs fine. Until you hit higher RPMs. Then, though it still runs ok, it starts pumping out black smoke. So doesn't "sound" like it needs to be replaced.

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[Sailmonkey]

Originally Posted by Kevin84

Ok, found out a little more about what's going on with this engine. She apparently starts and runs fine. Until you hit higher RPMs. Then, though it still runs ok, it starts pumping out black smoke. So doesn't "sound" like it needs to be replaced. Sent from my HTC6500LVW using Cruisers Sailing Forum mobile app

That sounds over propped to me

[a64pilot]

Black smoke is usually excess fuel or not enough air, still doesn't guarantee its not shot though, but if it has good oil pressure at idle when hot, and doesn't have any blue to the exhaust, it may be just a clogged exhaust elbow, or maybe fuel injectors, maybe

[a64pilot]

Or yes, overpropped

[Cheechako]

I think your boat is underpowered, so I would upgrade in HP if possible. Motorsailing into heavy chop, my guess is you dont move much....?

[a64pilot]

You know he started the thread by saying it was underpowered at 30 hp for 24,000 lbs.
But I thought 1 HP per thousand was acceptable, if it isn't what is?

[CarinaPDX]

Badly adjusted valves can also cause black smoke and lack of power. Adjusting the valves should be high on the list of tasks once the boat is purchased.

Underpowered? The context matters. It is definitely not underpowered for a traditional auxiliary. It is a little underpowered by modern motorsailor standards. Yes, there will be times where having an extra 10-20 hp would help when pounding to weather to get somewhere, but this should be relatively seldom and will if anything make the trip more miserable if shorter.

If the engine is fundamentally sound then unless the OP likes throwing around $20k it is not worth worrying about.

Greg

[Celestialsailor]

I've seen poor injectors do that. They can easily be rebuilt. 1hp per 1000lbs. is minimum. Against current and wind, 3hp per 1000lbs. is nice. I weigh 17,000 fully loaded and have a 46hp. Max power is at 2800 rpm. With current and wind, I run 1400 rpm. and hit 5kts. against wind(15kts) and a 2 kt. current, I run 1800 rpm and do 5 kts. so I do have good reserve power. I burn about 3/8 of a gallon an hour. If I had to really work the engine, say 2200 rpm. I would imagine consumption would be well over .5 of a gallon an hour. It's always a balance of power, speed and consumption.

[cwyckham]

Originally Posted by Kevin84

Ok, found out a little more about what's going on with this engine. She apparently starts and runs fine. Until you hit higher RPMs. Then, though it still runs ok, it starts pumping out black smoke. So doesn't "sound" like it needs to be replaced.

Sent from my HTC6500LVW using Cruisers Sailing Forum mobile app

Is this in gear or out of gear? If it's still smoking out of gear at high revs, then it isn't the prop, obviously.