Johnson 4 hp new impeller but still has prostate trouble

[wbmiller3]

I've got a late 80's early 90's 4 hp johnson that had no water flow at all until half throttle. Even then it just sort of dribbles out the exhaust. Replaced the impeller (old one looked fine) and no difference. Doesn't overheat but I'm sure it would if I ran at low rpm any length of time. It was in salt water with previous owner. Any idea's on flushing or cleaning out any deposits? Run it in a bucket of engine flush?

Thanks

 

[14ftgrumman]

Re: Johnson 4 hp new impeller but still has prostate trouble

Not really familiar with your engine, but possibly there is stainless steel wear plate under the impeller that should be changed out too. Also the housing, too. If there is a lot of clearance, it won't pump much water, as it's not pumping all the water that's in the housing.(leaking internally inpast the vanes of the impeller) Wish I could describe it better.

 

[2rz-fte]

Re: Johnson 4 hp new impeller but still has prostate trouble

my buddys tohatsu does that but when you drop it in the water it pees fine. just during flushing and idle does it barely wanna pee. it runs good so we dont mess with it.

 

[Vic.S]

Re: Johnson 4 hp new impeller but still has prostate trouble

Not following what you say about no water water flow and only dribbling out of the exhaust above half throttle.

The main exhaust outlet is underwater and that is where the bulk of the cooling water leaves. You cannot see it leaving from there!

AFAIK the 4 hp models do not have a cooling water tell tale, but you do not give the model number so cannot check for certain.

Are you just looking at water being blown out of the exhaust pressure relief port on the leg. If so you will only see a few drops or a mist from there and possibly none at low speeds. The real test is whether or not the engine is overheating. If it is not then maybe you are trying to fix something which is not broken.

 

[wbmiller3]

Re: Johnson 4 hp new impeller but still has prostate trouble

Thanks your prob right. I guess I thought it would pee out at idle like my 6 hp does. But it really doesn't have a place for that stream to come out like the 6 does. It runs fine so I guess I'll just leave well enough alone. thanks again for your replies.