interesed in a BF90

so

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saw a local ad for a 2016 Honda 90hp, it needs work. Talked to the seller, he bought it used a few months ago, took it out a few times. Last time out he heard ticking noise, checked oil after he got home found water in oil, local mech checked it and said #4 piston/rod needs replaced and head gasket is not leaking but couldn't confirm where the leak is from.
what could be the cause of the leak? what to look for when I go check out the motor (cylinder head has been removed so I guess i can check the cylinder walls). I've messed with a 85hp two stroke suzuki before but not these newer 4 strokes. Also can't seem to find a downloadable service manual on ebay for it, any pointer will be appreciated. thx
 
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racerone

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You will need a manual.-----And that is a job that requires a LOT of work.
 

airshot

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All signs that the motor was not cared for very well, what else will show up ??
 

MattFL

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So many possibilities. If it's not the head gasket, it could be a cracked cylinder, cracked head, hole in an intake or exhaust runner in the head, maybe a base gasket depending on the motor (I'm not knowledgeable on that specific model), etc.. Most likely it will need to be disassembled and inspected carefully to find the source. Also note that if it has been sitting for any time with water in the oil, especially saltwater, a lot more could be bad inside the motor from rust. If you want it for a fun project then go for it, but if the goal is a good running motor then that one might require more work than it's worth.
 

racerone

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To tear one of these down , I believe you first need to remove the lower unit.----Then work up from there.-----A lot of work.
 

ahicks

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A few thoughts. First, the Honda 90 is a pretty sturdy motor - making me wonder about the "local mechanic's" qualifications. My experience has been MAYBE 1 in 5 have a clue....have even had one of these pulled down? Thinking it's MUCH easier to condemn a motor and sell a new one for those with questionable abilities.....

These ARE a tough(er) motor to work on, especially if you're in a hurry. A HONDA manual (not Clymers) is an absolute necessity ($$$). So will will proper tools - like a torque wrench for example. They do come apart from the bottom up..... with the power head being the last major part removed.

As far as the oil and water mixing in a motor this age, I would be looking for signs of overheating. I've done a bunch of these because they sell cheap and aren't that hard to fix if you have some experience with them. An overheated motor can destroy a head gasket easily - and better than half of the one's I've done were fixed by replacing the head gasket with a lot of careful cleanup and reassembly involved. No guarantee here - just sharing some experience....

Then-
Exactly how was it determined the head gasket wasn't leaking?
Exactly what process was used to determine the rod and piston needed replacing?

Bottom line, I would not recommend a project like this to somebody that didn't already have a fair amount of mechanical experience..... -Al
 

so

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went to look at the motor. the powerhead was sort of taken apart and the cylinders have become rusty. will honing take care of it?

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MattFL

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That top picture is a ton of rust, I'm going to guess the cylinders are pitted deep enough that it's going to need more than a hone to fix it. Also the bearings inside the motor are also likely rusted, possibly the crank and rod journals too. Sure you can probably scrape the rust off, get it to free up and run, but I really doubt it's going to last a long time without a proper rebuild.
 

so

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That top picture is a ton of rust, I'm going to guess the cylinders are pitted deep enough that it's going to need more than a hone to fix it. Also the bearings inside the motor are also likely rusted, possibly the crank and rod journals too. Sure you can probably scrape the rust off, get it to free up and run, but I really doubt it's going to last a long time without a proper rebuild.

it's not frozen at the moment. i was able to turn the crankshaft with a wrench when i was there.
Also, any way to stop the rust from growing if i were to wait a few months before starting the rebuild?
 

ahicks

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it's not frozen at the moment. i was able to turn the crankshaft with a wrench when i was there.
Also, any way to stop the rust from growing if i were to wait a few months before starting the rebuild?
You could dry it best possible (I would use compressed air) then wipe it down with an oil soaked rag. Turn it over slowly to try and coat the rings, then oil it down again. Stored indoors out of the weather, that might buy you a couple of months.

If this motor is cheap enough, you might try looking around for another 90 with a serious lower unit problem, do a power head swap, and come out OK - IF - you need a 90.
 

MattFL

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it's not frozen at the moment. i was able to turn the crankshaft with a wrench when i was there.
Also, any way to stop the rust from growing if i were to wait a few months before starting the rebuild?
Buy a spray can of fogging oil and go crazy on it. The goal is stop the air contact with the metal.
 
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