70 hp Chrysler not pumping water at high speed

[frankd123]

Hi I have a 70 hp chrysler outboard (around late 60s I think) the problem is that when running at high speed the water pump doesn't stream any water.
At idle speed the water pump works ok and at middle speed the stream looks to be less

any suggestions on what could it be? do you think it is the impeller? by the way motor doesn't has a thermosthat istalled, the previous owner sold it to me as it is

thanks

 

[Darbyz71]

Re: 70 hp Chrysler not pumping water at high speed

Don't run ur motor ! Now that is a classic sign of a water pump that's either been sitting for some time or is just plain wore out. You need a new water pump before u chance burning ur engine up. What happens is the fins on the pump get preformed if they've sat a long time or there just wore down to the point of no return. At idle, ur pump is able to keep up but as your Rpms gain steam the pumps fins start failing and can't pump enough water for the motors demands. Replace your pump there $25 bucks or so and easy to install. Hope this info install helps out. God Bless

 

[Stachi]

Re: 70 hp Chrysler not pumping water at high speed

It would also be a GOOD idea to install a thermostat.......

 

[Darbyz71]

Re: 70 hp Chrysler not pumping water at high speed

Yes I agree, I missed u saying there isn't a thermostat installed. Yes with a good tight water pump and plates/housing installed you'll see water at high rpm's but your motor stil want be running at peak performance. Your thermostat regulates temp inside the motor thus creating the in spec operating range. Without a thermostat your motor will fight against a cold block giving you less performance while going almost unnoticable. Along the way with ur new stat make sure all your springs and grometts are also in good shape. Oh make sure you cover you new pump a d housing surfaces with vaseline to prevent burning up your new pump before water make it up to it. God Bless

 

[moparman]

Re: 70 hp Chrysler not pumping water at high speed

if your talking about the relief ports on the back of the motor ,they are mainly for low speed use, as the motor doesn't make sufficient exhaust pressure to force it out the bottom under the water[hence the term "relief port"],it allows it to bypass the bottom exhaust exit and go out the easier relief port on the back. As the boat picks up speed ,it's easier for the exhaust to go out the bigger opening at the bottom as the rpm's are increased and water is pushed out of the way via the lower foot. Hope i've explained it to where you can get the picture of how it works. If your not having an over heat issue, then the water flow is doing what it should do, but if you haven't replaced the impeller in the last 2or3 years ,then do so just as normal service. Hope this helps........MOPARMAN .............. ROLL TIDE