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My 1999 DF50, while old, had ~300 hours and developed low compression on cylinders 2 and 3. It was sluggish on water, eventually wouldn't start with all spark plugs in. It had also overheated after WOT on water a couple times during it's life. I took it apart and noted leakage across head of #2 and #3. Also, the wall of short block between lowest water jacket and oil housing area cracked due to corrosion near bottom of jacket, adjacent to crankcase. I picked out a lot of corrosion from water jackets of shortblock and head, some passages were completely blocked. I considered weld repair, but ultimately decided that both the head and short block were beyond repair. I received replacement parts from ebay: a used shortblock "with good compression" per the seller and a slightly used head with 2 anodes and cooling passages still have original paint. (My original head didn't have any anodes). I hope the future 1+2 internal anode configuration helps. I recognize that letting the engine warm up on the garden hose wasn't sufficient for avoiding corrosion with this engine, and will need to be more proactive in the future, maybe I'll try the vinegar/water bucket idea.
I ended up going ahead and separating the engine holder, oil pan, drive shaft housing and lower unit. The poppet housing had some corrosion around the poppet and the water tube seal, so I'm replacing those and doing a little sanding and touch up paint where it was corroded. I also noticed the head of the water tube retaining bolt broke off, so I need to fix that somehow
On all the housings, I've tried to clean out any corrosion from the cooling passages, and re-prime and paint where badly corroded except the cylinder water jackets because they aren't really accessible.
I'm preparing to put it back together, and have a few questions. Thanks!
After head gasket install and head bolt torque, I plan to try a low pressure leak down check as a precautionary measure before assembling the cams/chain/oil pump housing/etc. As I’ve never done this before, I suppose I’d be listening through the openings at the bottom of the shortblock for potential piston ring leaks, and through intake and exhaust ports for valve leaks (with a stethoscope). I also expect the total % leakage should be 10-20%. Any suggestions?
I'm leaning toward skipping oil pump rotor inspection because the Phillips head screws for rotor plate are tight, aren't budging with my 3/8" drive impact driver, and I don't want to break them. There were no signs of oil circulation issues, I was just following the service manual and thought while I had it apart I should check it out. Any suggestions how to disassemble?
If oil seals on upper and lower end of crankshaft appear okay, can I just keep them in-situ and continue using them? There was no oil leaking on my old shortblock, but now I'll have a different used shortblock.
Anything special I should do before starting this Frankenstein up for the first time?
I hope to use the boat in both fresh and saltwater. Anode options seem to be 55321-87J00=zinc, 55321-87J01=aluminum, which is best for combination use?
I ended up going ahead and separating the engine holder, oil pan, drive shaft housing and lower unit. The poppet housing had some corrosion around the poppet and the water tube seal, so I'm replacing those and doing a little sanding and touch up paint where it was corroded. I also noticed the head of the water tube retaining bolt broke off, so I need to fix that somehow
On all the housings, I've tried to clean out any corrosion from the cooling passages, and re-prime and paint where badly corroded except the cylinder water jackets because they aren't really accessible.
I'm preparing to put it back together, and have a few questions. Thanks!
After head gasket install and head bolt torque, I plan to try a low pressure leak down check as a precautionary measure before assembling the cams/chain/oil pump housing/etc. As I’ve never done this before, I suppose I’d be listening through the openings at the bottom of the shortblock for potential piston ring leaks, and through intake and exhaust ports for valve leaks (with a stethoscope). I also expect the total % leakage should be 10-20%. Any suggestions?
I'm leaning toward skipping oil pump rotor inspection because the Phillips head screws for rotor plate are tight, aren't budging with my 3/8" drive impact driver, and I don't want to break them. There were no signs of oil circulation issues, I was just following the service manual and thought while I had it apart I should check it out. Any suggestions how to disassemble?
If oil seals on upper and lower end of crankshaft appear okay, can I just keep them in-situ and continue using them? There was no oil leaking on my old shortblock, but now I'll have a different used shortblock.
Anything special I should do before starting this Frankenstein up for the first time?
I hope to use the boat in both fresh and saltwater. Anode options seem to be 55321-87J00=zinc, 55321-87J01=aluminum, which is best for combination use?