Merc 170 cooling problems 1986

[Clipsie]

I recently purchased an older boat that has an merchant 170 w/ alpha 1 out drive I have learned a little to late that those motors had cooling problems due to the fact that they have a alum block and a cast head ......with a sealed cooling system....the stator has been changed so I now am charging with a alternator ....is there anything that I can do to keep the motor running cool and prolong the life of the boat so I can enjoy it without sorting about cooking it?

 

[Faztbullet]

Re: Merc 170 cooling problems 1986

It should already have the larger heat exchanger but replace the impeller in outdrive every 2 years,make sure antifreeze is at 50/50 mixture,pressure cap is in good shape and never never start it without have water hooked to it.

 

[JerryIrons]

Re: Merc 170 cooling problems 1986

I have the exact same engine and year of boat, you have 170 horses of power there, lots of torque I think you will be happy with it. My boat is 18.5 ft long and I ran it all year long on lake erie with no complaints. Faztbullet has good advice, also I would make sure to check your coolant and oil levels before/after every trip. I bought a radiator cap with a temp gauge on it as well because I was paranoid. Get the good mercruiser muffs, the ones with the pin that goes through the outdrive, doesn't slip off and burn up your impeller. Also did you winterize? Very very very important. Water still in the block can freeze = cracked block = replace engine. The nice thing about the dual cooling system is that this boat is very easy to drain - one plug.

 

[guyaverage]

Re: Merc 170 cooling problems 1986

Eight years of 470 ownership tought me a few lessons about keeping this hot-headed beast running cool:

-Change the impeller every 2 years at most, every year is better.

-At least once a year, inspect the water hose in the bellhousing to make sure its in good shape, and check the water hose that runs from the connection at the transom (back behind the engine) to the heat exchanger. The way mine had been routed, it was rubbing against the engine and had kinked down to about 1/4 its normal size.

- Clean the heat exchanger. This involves a gallon of muriatic acid (Home Depot/Lowes), a big plastic bin large enough to hold the exchanger, old clothes, EYE PROTECTION, rubber gloves, and a constantly running hose, and baking soda (to neutralize acid spills if they happen). There are several write-ups on the Breezeworks 470 forum on how to do this, there might be here on iBoats too, though I havent searched. If you dont feel comfortable doing it yourself, have a radiator shop do it. The amount of crud and corrosion that have taken up residency inside the exchanger all these years will amaze you, and the effect it will have on running temperatures is worth every dime you pay a shop, or the $10 and 1 hour you spend on it yourself every few years.

 

[stonyloam]

Re: Merc 170 cooling problems 1986

?????? There is (anyway should be) NO water in the block, it should be permanently filled with 50/50 automotive type antifreeze and the block does NOT need to be drained to winterize. Only the heat exchanger needs to be drained.

 

[JerryIrons]

Re: Merc 170 cooling problems 1986

Yes you are right, if water is left in the system and allowed to freeze, the block will not be affected, but the heat exchanger will, (and possibly other things like outdrive if left up) and be ruined so in the end it's not as big of disaster, but the point I was trying to make is to make sure you winterize the engine.

And just to clarify for anybody else, my heat exchanger has 2 drain plugs. One is for the closed cooling system, the other one (aft) is for the freshwater drain. Make sure you use the correct drain plug or you won't remove the water you are trying to.

 

[stonyloam]

Re: Merc 170 cooling problems 1986

Yeah I kinda thought you were talking about the heat exchanger, but the OP is new and I wanted to make sure he did not get the wrong impression. Back to the OP, the thermometer cap is a great idea, am going to add one myself this coming season. The 470 should have a 165 F thermostat and operating temperature is 165 to 200 F, closer to 165 is better. An annual compression check and cooling system pressure check are a good idea, they are good information for monitoring the condition of the head gasket and cooling system. You can borrow the tools from Autozone.

 

[Clipsie]

Re: Merc 170 cooling problems 1986

thank you

 

[JerryIrons]

Re: Merc 170 cooling problems 1986

Stony I'm glad you said something, I re-read my post and it isn't as clear as it could have been...
Also that's a good idea of annual cooling system pressure check, I hadn't thought of that but can see how having a baseline of your system will help you when there is a problem. (I do check compression) My thermometer cap at the least tells me that my gauge on the dash is accurate, I mean what are the odds both could be wrong