Alarm during idle with 1988 80 HP MErc Outboard (newbie)

[kaempfe]

When I first get the boat in the water and run a low speed for a while, I get an alarm but it is not constant. It chirps a bit and goes off. Sometimes it may alarm a bit longer but goes away especially if a throttle up a bit. The mechanic said it sounded like it was overheating and the water pump impeller might be going bad. But it usually only does this early on or after I throttle down and idle. But this was just from hearing me describe the sound - he has not witnessed this himself. I also heard it could be oil mixture or oil flow related.

Any ideas? I can't put it in the water right now so I'm going off memory. I'm trying to put a list together of what I need to fix up before getting it back in the water.

If it is impeller related....how hard is the water pump to replace myself? Can you give me a brief checklist of what I would need to do so I can determine if I have the time to tackle this myself? I am willing to do it but I have two young children and commute an hour each way to work so time is not easy to come by.

Thanks!
Scott

 

[CharlieB]

Re: Alarm during idle with 1988 80 HP MErc Outboard (newbie)

If the water pump impeller is much over two years old it IS suspect.

Order up a water pump rebuild kit and a service manual. You can check here to see if your manual is still available for download.

http://forums.iboats.com/showthread.php?t=309079&p=2072211#post2072211

The whole job should be done within an hour, even with the kids hindering, I mean 'helping'.

 

[Texasmark]

Re: Alarm during idle with 1988 80 HP MErc Outboard (newbie)

When you get your impeller out if it is in really bad shape....where it looks as if it can't pump water very well, you might replace, or at least run a kitchen stove pot of water test on your stat...if you have one. I had an '84 85 4 in line and later a 115 tower sold to me new as a '89 model (been told on here that '88 was the last year they were manufactured.....but could still be marketed in '89 as an '89 model) and neither had stats. Don't remember when Merc dropped the old castings and went to the new 3 cyl enignes which have stats. Anyhew...if you do, opening temp is stamped on the pellet....currently 143F is the temp.

Mark

 

[kaempfe]

Re: Alarm during idle with 1988 80 HP MErc Outboard (newbie)

I have a 3 cylinder. I have a service manual but it is a bit vague for my liking and covers a period of time so I need to first decipher which instructions to follow. I'll see if I can figure out if it has a stat. It ceraintly has not had the impleer changed in over 5 years - it has not been run much but it has seen numerous winters outside. I think this is needed.

The mechanic gave me a rough estimate of $325 to replace the water pump. Will they automatically just replace the whole pump or will they charge less to replace the impeller. It seems high if it only takes an hour and the impeller is cheap.

I will look at this in ore detail this weekend....thanks!
Scott

 

[kaempfe]

Re: Alarm during idle with 1988 80 HP MErc Outboard (newbie)

One more thing....how would I know if the water pump itself, and not just the impeller, is bad? What are the tell tale signs or tests that I can do??

 

[Texasmark]

Re: Alarm during idle with 1988 80 HP MErc Outboard (newbie)

Both the pump and the impeller can wear out. The impeller is a rubber "toothed" device which is driven by the drive shaft and acts as a displacement pump at low speeds and centrifugal pump at high speeds. The blades are made of rubber and need to remain flexible to perform the intended function.

Failure mechanisms are usually blades getting brittle (with age and no rotation) and breaking off, or taking what I call a "set" whereby the pump has remained inactive and the blades that were compressed during that time remain compressed when the pump is set in motion and do not expand out to the walls of the pump to force water into the powerhead whereby it is unable to pump the required water to the powerhead at low speed.

The SS liner of the pump can wear also, but it takes a long time, depending upon quality of water. It's amazing how a piece of rubber can cut into steel, especially stainless steel, but it does, in all kinds of applications and in doing so, produces a leak.

Additional wear parts with/in a kit are seals for the crankshaft, especially the one that fits below the pump and seals the lower unit. It is extremely important as it keeps water out of your gear box.

My impeller was replaced back in 2004 and my pump works perfectly. I boat in clear water and when not boating, I "touch" the start button every week or so to keep the impeller rotating to different positions.....compressed and relaxed. I usually run in a small lake and have an over temp alarm. If it were to fail me it wouldn't be that big of a deal. If I were going to run off-shore it would be a totally different story.

If you have a stat, and with a 3 cyl you probably do, it is a bulge (separate cover) on the rear of the engine's rear water jacket (that the spark plugs are mounted through). Probably at the upper left corner and is held in place with 2 screws. Obvious once you know that you have one and look at the rear of the powerhead.

I usually just use blue RTV to glue my cover back after inspection. I am not close to a dealer and the RTV does an excellent job in making the torn up gasket reusable.

Mark

 

[BatDaddy1887]

Re: Alarm during idle with 1988 80 HP MErc Outboard (newbie)

It is a fairly easy fix to change the impeller yourself. You need to get the new kit which consists of a new impeller and gaskets (about $20), put the motor in forward gear, drop the lower unit....don't forget the hidden bolt under the trim tab anode, remove the pump housing bolts, change out the parts and make sure you put the shaft key in place as you found it. When replacing the LU (lower unit), you may need to turn the prop to line up the shaft for correct insertion. There are numerous threads here with detailed info and on youtube you can see several people do it on Merc engines. Your manual should also cover this. Teach yourself to save money by doing it on your own.

 

[kaempfe]

Re: Alarm during idle with 1988 80 HP MErc Outboard (newbie)

Thanks....I will order the impeller kit and go from there.

 

[kaempfe]

Re: Alarm during idle with 1988 80 HP MErc Outboard (newbie)

Hi.

The local shop had the impeller but the not the kit with the gaskets. This is the 1988 80 HP 3 cylinder motor (b373411) which has the metal housing. The mechanic/owner seemed very knowledgable and said this was a very robust impeller design and I didn't need the gaskets, metal plate, etc. He told me to assess the condition of the gaskets and he can get them if need be. He said just make sure the plate has no hard water deposit etc.

I believed him but now I'm second guessing myself. I really wanted to do it this weekend but if I decide to wait for the gaskets - it might through me off my schedule.

So....I'm looking for a sanity check. Am I crazy to pull this all apart and only replace the impeller or should I bite the bullet and switch the O-ring, metal plate and gaskets that are in the kit that I would need to order?

Thanks!!
Scott

 

[kaempfe]

Re: Alarm during idle with 1988 80 HP MErc Outboard (newbie)

How do I find the stat? Is it near the impeller or somewhere else? I can't find it in the service manual. IT is a 1988 80 HP 3 cylinder (B373411)

Thanks
Scott