Honda 50HP Cooling system issue (1999)

[MattFL]

I'm looking for someone who is very familiar with the 50HP Honda cooling passages for help on how to clean debris out. I've got a 1999 50HP Honda that suddenly developed an intermittent pee stream problem. The stream has good solid pressure, then suddenly the pressure drops very low and sometimes to a dribble. I've seen it happen while cruising, very solid stream then suddenly almost nothing. It's as if there is some debris inside the cooling system somewhere that suddenly blocks a passage way. It intermittently both in the water and on the flush muffs. If I turn the motor off and on again a few times, the stream will eventually return. It must still be getting good flow inside the motor because I've noticed the issue while cruising for extended periods of time at 5000rpm and it did not overheat, but this is our ocean boat so I really would like to get this resolved just in case. The blockage is not at the outlet for the pee stream as I've stuck a very thick and long weed whacker string up the tube while it is running to try to clear it out and that makes no difference at all. I've also replaced the water pump impeller (twice) and thermostat, but the problem persists. The wear plate and pump cup both look great, smooth and no grooves, and when it's working the pressure is excellent. All of the water passages in the lower unit are clear. Has anyone seen this before on a 50HP Honda?

Motor history; I bought this motor new in 1999 and it has been a year round saltwater motor since then. It gets flushed after every use and runs fantastic, so I would really like to get this fixed before it causes a real problem. I'm the only one to have serviced this motor and I've put numerous pumps in it over the years and no impeller has ever come out missing any pieces so I'm not sure what's in there.

 

[Sea Rider]

You have a 20 year oldie in use, if the motor was used exclusively on salt water and flushed after use, doesn't matter for how long you have flushed it with muffs, barrel as has already collected salt layers, crusts inside the powerhead's water passages. If plan using it at open waters with long cruises at speed. Need to remove the cylinder head, the exhaust cover and the thermo cover and mechanically scrape off all salt contents. Check water pump and thermostat condition, if so-so change both.

Short long story...This motor is flushed with high water pressure on muffs soon after returning to Terra Firme, has never had an overheat. The cylinder head, thermo and exhaust covers were removed after 500 worked hours for a full water paths
maintenance, check what was found...




Why is it that all boaters waits till the motor overheats, water paths periodic maintenance is all what the motor needs to run cool at speed for long time periods. Who does this type of preventive maintenance. No One LOL!!

Happy Boating

 

[MattFL]

Thanks for the reply. I'm sure I'm well over 1000 hours on this motor, it's on the 3rd hour meter and that one reads almost 400 hours (I didn't track where the previous ones died). I'm also sure there is salt built up inside, and it's probably a chunk of that which has broken off and is now causing the issue, but I will say that my thermostat cover looks no where near as bad as yours last time I changed it (a few months ago). I did a lot of googling and apparently this is a somewhat common problem on Honda's. I'm going to try removing the lower unit and the t-stat housing, then backflushing through the t-stat housing. This seems to have helped resolve the issue for some people. After 20 years in salt, I'm afraid removing the head and exhaust plate would lead to countless hours of fixing broken bolts. Keep your fingers crossed!

 

[Sea Rider]

Flushing through the stats won't help a bit if already having excesive salt built up layers inside the powerhead. My powerhead has a side flushing port attached to the exhaust cover which is used to flush the powerhead with a Karcher washing machine set at low pressure with thermo removed from cylinder head as to have 0 water restriction in the water passages while flushing with motor OFF.

Guess what, didn't clean the water passages whatsoever, probably only good for removing small salt crusts build ups inside the powerhead. If my motor didn't have any overheating issues with such salt build ups inside the powerhead, now imagine the salt quantity that will find on yours with already overheating issues...

Accoding to my experience dismantling powerheads on motors used on salt water, it's quite normal to break any bolt while is being removed due to salt intrusion on the threads that inevitably will harden and seize up the bolts....

Happy Boating

 

[MattFL]

I think you misread my original post; so far I've had no overheating at all, just something floating around that temporarily restricts the pee stream.

 

[ahicks]

I spend a lot of time messing with the 35, 40, 45, and 50hp Honda's. Call them a hobby if you like. I've seen the issue you are talking about on occasion. The problem with the Honda's that have been around sea water a lot is they have a tendency to break off bolts when pulling them down. Point being here you don't want to pull them down any further than necessary.

There's sort of a reservoir under the power head that might have a loose piece of crud causing your evil. The pisser is routed from this "reservoir". When they are doing what you are talking about they get a couple of short shots of air pressure while the engine is running on muffs.

What I generally do if I run across and engine that's full of lime, sand, or crud, is pull the lower unit and the t-stat housing. Then use air pressure to blow through the pisser backwards, and then the water pump tube. Don't use a LOT of pressure for fear you'll blow a good gasket out of place! Just a series of short spurts and see if you don't blow some crud up out of the t-stat housing. You could also pull the intake manifold and check there. There's an anode hiding in plain view there. If you haven't checked that lately, might be a good plan.

I would not pull the exhaust cover unless it's been pulled regularly. If one of those bottom bolts breaks, as they do frequently, you'll be pulling the short block for sure to drill and tap.

You can also hook a garden hose right to that water pump line. Slip a piece of water hose over it and clamp it. That'll rinse things out for sure, motor running or not.

 

[ahicks]

On the above, when rinsing an engine using a water hose hooked to the water pump tube, I should have mentioned that you want the t'stat housing removed during that process as well.

 

[Sea Rider]

Yep sorry skipped the having no overheating isues, when experiencing them you'll know what to do. Is not that motors are big bolt breakers, the issue is that nobody retorques exhaust and cylinder head gaskets's bolts soon after a new motor has ended its break in period or when new gaskets have replaced old shot ones mainly because not knowing anything about that procedure, need to take the motor back to the dealer for that job with added hand labor expense or in need to buy a good quality precise torque wrench for a DIY retorque work.

Will find that new gaskets have compressed a bit due to heat and what was factory torqued to will not remain same. If you retorque both gaskets back to specs you'll have fever chances of salt water intrusion on bolt's threads and consequently seizing and breaking exhaust and head bolts when removed.

If that motor was used religiously all year round on salt water for the last 20 years, expect to have huge salt layers and crusts inside the powerhead. Begins with peeing issues and will worsen over time developing overheating issues. If flushing with compressed air and removed thermo as suggested and still with no avail solving the peeing issue, you know already what's going on inside the powerhead,

Happy Boating

 

[MattFL]

Just following up; removed the lower unit and thermostat, blew air through the pee line then water down through the motor from the thermostat opening. A surprising amount of stuff came out the water pump tube! I stopped the water, let the water drain out, blew some more air then hit it with water again and more stuff came out. I repeated this process several times and kept getting more stuff, and some relatively big pieces. I'm in the middle of working on it now and got stormed out so I'm posting this while waiting for it to blow over, but here are some pictures of the bits in a 5 gal bucket for anyone else who might have the same issue, and some pictures just for reference of a 20 yr salt motor that gets year round use and flushed after every use. If the rain ever blows over, I'll get it put back together and I'll post back the results after testing.

 

[MattFL]

OK It's back together, and on the garden hose it's peeing significantly stronger, but I won't know if the problem is fixed for sure until after a few trips.

 

[Sea Rider]

If thermo housing looks awful, imagine all the rust, salt crusts already built inside crankcase which isn't seen unless having some sort of x ray vision LOL.

The only way to find out if motor will overheat is taking the combo for a long wot run. Motors usually don't overheat at idle, fast idle, say less than half throttle, but will eventually overheat passing half throttle as the internal temp rises.

Happy Boating

 

[MattFL]

I have no reason to believe it would overheat, it hasn't yet and gets run hard almost every outing. I'm just trying to fix a peeing issue, not an overheat issue. The thermostat housing isn't bad a tall, the cover has practically nothing on it and there's just a little crust in the passages, nothing major.

 

[ahicks]

I'd agree with you Matt, but I would add that I've worked on a lot of "salty" engines just like yours, and would encourage you to keep a close eye on it. They're famous for corroding in the area of the head gasket, to the point the gasket surface area shrinks/is eaten away to the point there's nothing left to seal. Could happen on the head side of the gasket surface, or the engine block side. Watch for a sudden loss of compression in one cylinder, or mixing water with the oil. Taken care of promptly, often there's a lot of life left in them afterward. I buy a lot of freshwater parts (heads, blocks, short blocks) from the midwest to repair these issues.

There's also an issue with the lower units. If the bearing carrier isn't removed and cleaned of corrosion occasionally, it's going to split the lower unit. Not a huge disaster, but it will require that the carrier be removed and the case welded up by a qualified welder. -Al

 

[MattFL]

Thanks for the tips! I'm sure corrosion will be the downfall of this motor at some point, but hopefully there are still some years left. It's probably not worth fixing any major issues on a 20+ yr old salt motor due to how many fasteners are sure to break off. Realizing this motor is getting long in the tooth, I bought a boat us membership for the first time a few weeks ago.

In regards to the lower units; have you seen any bearing issues? Several years ago my lower unit bearings started making a faint whirring sound, I couldn't tell you how many hours on it as there were a few hour meters and several years with no hour meter during its tenure, but I've always wondered if this was a common issue on this model. Rebuilt lowers don't have a good reputation locally so I just bought and entire new lower unit. Only about 330 hours on the new lower unit so hopefully it has some years left in it too. Keep your fingers crossed!

 

[ahicks]

I would make removing that bearing carrier part of your annual maintenance if you are looking to get max life from it.

 

[MattFL]

Time will tell if the peeing problem is 100% fixed, but I've had it out 2x now and the problem has not recurred.