replacing impellor vs. water pump?

[duckinit]

I have a 1977 Mercury model 200 20HP motor and I am having water pump / impellor problems. I have owned the motor for 5 years and have done the basics with it - changed plugs gas lines and have tried to keep the gas as fresh as possible. I started to notice about a year ago that the engine was not spitting water the best. It spit water but was not a hard stream or water. This year I ran it once and ran great, but in preparing for another trip I started the engine with water muffs on the motor and I just got a trickle of water to come out. After it did not start spitting I shut the engine down. I am pretty sure that over the years the impellor needs to be replaced. My question is can I do it myself? I am fairly good at taking things apart and putting them back together, or am I better off leaving this one and the headaches with it to the professionals? If I can do it I have heard anything from dont waste your time replacing just teh impellor do the entire water pump assembly. I have the Seloc engine repair book for this model engine. Any advice is apprectiated. Thanks in advance to any help. The People at Iboats and Iboats forum are the best.

 

[WillyBWright]

Re: replacing impellor vs. water pump?

You won't know until you get in there if you'll need a whole pump or not. If you want to do it all in one shot and not have to run for parts, buy the whole pump. Mercury's pumps don't include the base. You have to get that separately. Sierra pumps come complete. If you have the manual and a few common tools, you can do that job yourself. The hardest part is getting it back on the motor, and that should be expalined pretty well in the manual. Good luck.

 

[JasonJ]

Re: replacing impellor vs. water pump?

It is very easy, and yes, just replace the entire pump. You can get away with replacing just the impeller, but you get the best result from replacing the entire pump. The surfaces that the impeller rides against can become grooved and worn over time, which can reduce the pressure. You can inspect the surfaces and if they are smooth, they may still be usable. One other thing, the tell-tale output always seems reduced when running on muffs when compared to running in the water. On my 69 Merc 1250, the stream is not that great on muffs, but is quite strong when in the water. Either way, good luck...

 

[jason621973]

Re: replacing impellor vs. water pump?

just did it on my 69 800 today hardest part was getting lower unit back on

 

[BW23]

Re: replacing impellor vs. water pump?

Get the complete kit.<br /><br />During reinstallation of the lower gearcase, it is much easier to allign the shift shaft if you disconnect the shift cable from the linkage.<br /><br /> Make sure the gearcase is in neutral and the motor shift linkage arm is in neutral.