Replacing impeller. How often? Good Maintenance Manual?

[normo]

My comments and recommendations:
1) Impeller life can't be measured in years or even engine hours. Just a few minutes in heavy sand can do a lot of damage to an impeller. I suspect that running the impeller dry due to sea weed clogging the intake would overheat the impeller and shorten its life. If you want peace of mind you should inspect the impeller at some interval that a savy mechanic can help you with. Every two years works for me.
2) Check the water cooling stream frequently. Carry a coat hanger wire to unplug the hole if it gets clogged.
3) Buy a shop manual (approx $36 for a Tohatsu 50) and learn how to do the basic repairs. Changing an impeller is not a 15 minute job but it can be done if you can get into shallow water.
4) Carry the shop manual, tools and a few spare parts like plugs, impeller, gas tank connector, bulb etc. so you can make some repairs yourself. Trips can be ruined if you have an engine problem and service/parts are not readily available.
5) Replace or at least inspect the impeller every year or two depending on your usage. The side benefit of this is that removing and lubricating the bolts will help prevent them becoming frozen into the case threads. Freeing frozen bolts can be a frustrating and expensive ordeal.

[Catigale]

Replace or at least inspect the impeller every year or two depending on your usage

My two cents - the impeller for my MERC BF was $15....once I drop the lower unit and get it all apart for inspection...the new one is going in regardless..

the labor is the barrier to this job imho

[Dimitri-2000X-Tampa]

Ive been using Seafoam for years, its a great product. I cant find any here in Daytona so whenever my friends from Minnesota come to visit I have them bring me some. Just used it on my lawnmower, cleaned it out and now it runs like new.

Robert, Napa auto parts in Tampa carries both the spray and the liquid seafoam. For that matter, so does discount auto parts. You might try those in Daytona.

I'm also in that club of people waiting to change the impellor one of these days. My Merc 50 BF is 5.5 years old now and I expect it has the original in it. When it hit 3 years, I bought the replacement but still haven't installed it yet. Hope to find the time soon...but haven't had much lately.

[Rich Plumb]

I have an older Nissan 50 (1999) with about 350 hours on the engine, after five years of use. This summer I had a failure of the shift dog in the lower unit. While the lower unit was removed, I decided to go ahead and get the kit and change the pump impeller. I did not have any difficulty removing the four bolts holding the pump housing or changing the various pump parts. When reassembling, I used anti-seize compound on the threads and a little petroleum jelly on the rubber pump impeller.

One word of caution when reassembling the Nissan/Tahatsu lower end onto the power head. There is a long water feed tube that extends down from the power head and fits into a rubber grommet on top of the water pump housing. The first time I assembled the lower end on to the engine, that grommet had slid up the water feed tube and was not making a good seal at the pump housing. That caused the output of the pump to leak out with very little water pressure at the power head. You will know this if there is very little water from the pee hole and a lot of water gushing out between the power head and the lower unit. The solution, for me, was to lubricate the outside of that long water feed tube with petroleum jelly and make sure that the grommet was secure on top of the water pump housing before reassembly.

~~~~~~~~_/)~~~~~~~~
Rich Plumb, "Plumb Crazy"
2000, 26X, Covington, WA

[crackles]

Thanks for that.

An old mechanic friend has suggested a cup of metholated spirits into a full tank every few months is supposed to disolve any water in the tank and also cleans the carbi. Four stroke engines of course. Seems to work.

[midget]

Very strange! Due to this thread, when I came back in yesterday,I noticed nothing coming out of the P-hole ( Merc BF 50) The really wierd part is - no alarms, no noise, and no trouble getting home. Plugged in the waterhose when I got home and same thing, no P! Luckily the boatlift builders that were supposed to start building our lift at the end of October brought their barge today!!! Any ideas, folks? The kicker is NO ALARMS?!?!

[Rich Plumb]

I've seen this before where the tube that feeds the pee hole is plugged with a piece of weed or crud picked up in the water. Try doing a Roto-Router, by running a length of soft wire up the pee hole, while the motor is running.

~~~~~~~_/)~~~~~~~~
Rich Plumb, "Plumb Crazy"
Covington, WA

[Catigale]

I once gave the hose on a Merc BF a twist while attached and twisted the pee hole hose in to a kink....DOH!!!!!!

[Mark Prouty]

I've seen this before where the tube that feeds the pee hole is plugged with a piece of weed or crud picked up in the water. Try doing a Roto-Router, by running a length of soft wire up the pee hole, while the motor is running.

~~~~~~~_/)~~~~~~~~
Rich Plumb, "Plumb Crazy"
Covington, WA

Turning the motor off then on again several times can also dislodge a grain of sand.

[kmclemore]

Mud-dauber bees like to make nests in my motor's bleed-tube... I carry a bit of wire in the toolkit specifically for clearing it.

[Dimitri-2000X-Tampa]

I really need to learn when to keep my mouth shut...seems I must have jinxed myself with my previous post in this thread. I went out last weekend and my alarm went off...I'm assuming because of overheating. Also, the motor started running crappy, missing, etc. so I wonder if that is related too. It had run fine the last time a couple weeks earlier when I pulled the kids around on a tube.

There is water coming out of the p hole although not at a particularly good pressure. Water is really warm in FL this time of year so I suppose that does not help. I tried reaming the p hole and the intake holes with the inside of a pen...didn't seem to be any significant blockages but I have had a lot of mud daubers around the boat lately and some have mudded inside the cabin too.

What do you guys think, time to replace the impeller or could those mud daubers have caused a blockage further up in the plumbing enough to cause the flow to go down enough to overheat? The alarm started going off pretty quick after I started it...hope it isn't oil pressure related.

I presume there is a thermostat in there somewhere..maybe that is not opening right. When you drop the lower unit to replace the impeller, can you get to all the passage ways to make sure there are not any other problems? I have the 2000 Merc BF 50.

[Dimitri-2000X-Tampa]

Unbelievable...I went out yesterday and I got an overheat warning in cooler bay waters. I had replaced my impellor a few months ago but didn't get to use the boat at all until a week ago. I had tested it with the rabbit ears and got good pressure. Put the boat back in the water and got good pressure, took one slow speed trip for 10-15 mins and didn't have any problem. Then I went out for about an hour up to slow planing speeds around 4000-4500 RPM, no problems. On the way home, I decided to open it up all the way for a bit and after a few minutes of that, the overheat warning went off. Pee stream was now weaker but still coming out, tilted the motor up hoping to find a bag on it or something but it wasn't obstructed so I went the rest of the way home at slower speeds and it didn't overheat again.

This impellor is basically brand new and I'm figuring the installation should be good if it worked well for a while and seems to have enough pressure to handle lower RPM's. I'll try to ream out the pee hole just in case there is something in there but I have a feeling that is not going to help. Now I am second guessing my decision to use the old water pump housing (new impellor and plate). It did seem to have some slight grooving in it but I wouldn't have thought that would have made that much of a difference at high engine speed.

Anybody know what the symptoms of a wornout water pump case would be or have any other ideas?

[Catigale]

Yeeks that is a tough one Dimitri...is the reduced water flow now apparent at low rpm too? I guess that would point to the case being the problem.

This might be one of those cases where the Smartcraft thing could help you diagnose the problem (which could even be a bad sensor!)

I doubt you want to layout $1000 though...

[Ron]

The Honda owner's manual says nothing about impeller replacement. Does anyone have the service manual for Honda's BF 50 and know what it says concerning the impeller?

I was going to purchase the service manual, but now I'm not sure if they have a typo or if I would end up with the wrong manual. The site at : http://www.repairmanual.com/marine/4/12878 says,

OFFICIAL HONDA BF50 (5HP) MARINE MARINE SHOP MANUAL

click here for larger photo Provides service, repair and maintenance information for the Honda BF50 (5hp)Marine Marine engines.

Isn't the BF 50 a 50 HP?

[PeteC]

Isn't the BF 50 a 50 HP?[/quote]

Yes, the BF50 is the 50 HP Honda.

Call them to make sure it is the correct manual.

I have a factory Honda manual that came with my used 2001 50 HP Honda. The manual has a 1991 date on it but so far it has matched the motor. I used it to guide me on replacing the water pump impeller last spring.

Hopefully Honda has a manual with a more recent publish date.

The factory manual is well worth the money.