Possible 470 exhaust leak, yes I know what they say about them, run away.

[bently]

I have a 1977 Glastron SSV 175 with a Merc 470, I got it out of storage and just before I reinstall the heat exchanger end caps I fired her up and I could see exhaust smoke coming out of the uncapped heat exchanger. Does that mean I have an exhaust leak, bad gasket or a crack somewhere? My oil is nice and clean with no water in it, when I ran the motor for the short time it seamed the closed cooling system built up alot of pressure, could exhaust be getting into the antifreeze also, thanks.

I appreciate any help, I know I will get a little ribbing but that makes this site so great.

 

[Don S]

Re: Possible 470 exhaust leak, yes I know what they say about them, run away.

I have a 1977 Glastron SSV 175 with a Merc 470, I got it out of storage and just before I reinstall the heat exchanger end caps I fired her up and I could see exhaust smoke coming out of the uncapped heat exchanger. Does that mean I have an exhaust leak, bad gasket or a crack somewhere? My oil is nice and clean with no water in it, when I ran the motor for the short time it seamed the closed cooling system built up alot of pressure, could exhaust be getting into the antifreeze also, thanks.

I appreciate any help, I know I will get a little ribbing but that makes this site so great.

No, it means you need to put the end caps on the heat exchanger before running it so the water will get to the exhaust to cool it, or you will burn everything up.

 

[EddiePetty]

Re: Possible 470 exhaust leak, yes I know what they say about them, run away.

Don is dead on the money! But why would you run the engine with the end caps off? You did have the muffs on...didn't you?
If not.....the water pump (at least the impeller) is shot.

 

[stonyloam]

Re: Possible 470 exhaust leak, yes I know what they say about them, run away.

That was probably exhaust coming from the hose attached to the exhaust elbow, that hose is normally filled with water exiting the exchanger into the exhaust to keep everything cool. Starting without cooling water coming into the exchanger was unwise at best! You have for sure trashed the impeller in the outdrive and may very well have burned up the the exhaust shutters. Under no circumstances start that engine again without cooling water flowing through the exchanger. Before you even think about putting it in the water you need to replace the impeller and pump housing. The 470 is very sensitive to overheating so you need maximum cooling water through the exchanger at all times which means a impeller and pump housing in top shape. Good luck.

 

[achris]

Re: Possible 470 exhaust leak, yes I know what they say about them, run away.

I'll add to that... You may have also melted the water pocket cover in the bottom of the top housing. If you've done that too.... You'll get overheating problems regardless of how many water pump impellers you put in... When you split the drive to do the water pump, have a look up into the top box and THOROUGHLY check that water pocket cover.

 

[bently]

Re: Possible 470 exhaust leak, yes I know what they say about them, run away.

Yes, I was planning on replacing the water pump impeller and etc. I ran the engine for like 30 sec. If that 30 sec will do that much damage, everytime you start your own 470 on muffs or in the lake everone needs to replace everthing. You do not get instant water flow through everything in 30 sec.

 

[stonyloam]

Re: Possible 470 exhaust leak, yes I know what they say about them, run away.

When you start your engine on muffs or in the water the pump housing is already full of water and so is the exchanger so the water flows almost immediately (just cranking the engine over should start the flow). The problem comes when the dry impeller rubs against the dry walls of the housing, and the damage can occur very quickly. Similarly unless the water from the exchanger is being dumped into the exhaust to cool the gasses damage to the rubber parts can occur.

 

[achris]

Re: Possible 470 exhaust leak, yes I know what they say about them, run away.

This is a scan from one of the Mercury technicians training handbooks. Have a look at picture #3, that was 30 seconds. If you think you didn't do any damage, go right ahead and run the engine, but you'll be back here with "I overheated my 470, what now?" As well as fixing the water pump (and whatever else has been scorched) you'll be up for some very expensive repairs of the engine too.... So, fix it now (cheapest option) or fix it later (expensive option), you choice.... But you will be fixing it, one way or the other...

Chris......

 

[Rake722]

Re: Possible 470 exhaust leak, yes I know what they say about them, run away.

Only way to find out if its burnt is by putting her in the water and test drive.
I agree with the others having had alot of unwanted experience of late.

In my case the water pickup hose was leaking and lead to an overheat.

I replaced the impeller 3 times and the full WP housing with OEM Mercruiser.

 

[bently]

Re: Possible 470 exhaust leak, yes I know what they say about them, run away.

I should have listed the fact that the PO plumbed in two 3" heat exchangers. Can this stay as is or should I look for a 4" and get rid of both 3" heat exhangers.

Can a new water pump even keep two 3" heat exhangers full while out on the lake?

 

[stonyloam]

Re: Possible 470 exhaust leak, yes I know what they say about them, run away.

Sure, should be fine. In fact if the exchangers are clean and the impeller and pump housing are in top shape ONE 3" exchanger will work. The main reason (IMHO) that they went to a 4" exchanger is that people were neglecting the impellers which led to reduced raw water flow through the exchangers resulting in overheating. The 4" exchanger gives more room for error. There are plenty of 470s out there with 3" exchangers that are running just fine. So if you instal a new impeller and housing and change the impeller at least every other year you should be OK.

 

[achris]

Re: Possible 470 exhaust leak, yes I know what they say about them, run away.

I should have listed the fact that the PO plumbed in two 3" heat exchangers. Can this stay as is or should I look for a 4" and get rid of both 3" heat exhangers.

Can a new water pump even keep two 3" heat exhangers full while out on the lake?

Are these heat exchangers plumbed up in series or parallel? It will only work properly if they are in series, and the 2 water flows (raw water and engine coolant) are running in opposite directions.

 

[bently]

Re: Possible 470 exhaust leak, yes I know what they say about them, run away.

They are in series, the hoses go through one then the other. There are no "Y's" in the connections to run them in parallel.

 

[achris]

Re: Possible 470 exhaust leak, yes I know what they say about them, run away.

They are in series, the hoses go through one then the other. There are no "Y's" in the connections to run them in parallel.

That's a good start. Does the water flow through each side of them run in opposite directions?

 

[bently]

Re: Possible 470 exhaust leak, yes I know what they say about them, run away.

Does anyone have a diagram with shows how a single 3" heat exchanger should be plumbed. When I try to view the service manual, my browser locks up. I am planning on completely replacing the water pump and then get back to one 3" heat exchanger. The end caps for my current heat exchangers are worped and do not seal all the way around, can I just have a shop make me some out of steel plate that is a little thicker so it will not bend when the bolt is tightened?

 

[achris]

Re: Possible 470 exhaust leak, yes I know what they say about them, run away.

 

[natemoore]

Re: Possible 470 exhaust leak, yes I know what they say about them, run away.

When my brain farted a couple years ago, I smoked the impeller in less than 30 seconds of running without the muffs on.

 

[bently]

Re: Possible 470 exhaust leak, yes I know what they say about them, run away.

Thanks for the diagram. I have seen the car guys use this motor in street rods and have an upgrade to the closed cooling system water pump that eliminates the cam seal issue. If your motor does not have the power steering, they mount either a belt driven or the newer electric auto water pump. They cut off the end of the cam and use epoxy to seal the openning. They then seal off the inlet to the head and add a nipple, make block off plates for the new water pump add nipples to the elbows and use hose to connect the pump for the propper flow. No more water in the engin oil, ever.........this is the link to their post (pages 6 & 7), they also have a tons of performance upgrades for this motor, lots that are bolt on.

The elusive 224/3.7 MerCruiser banger - Page 6 - THE H.A.M.B.

 

[stonyloam]

Re: Possible 470 exhaust leak, yes I know what they say about them, run away.

I have seen the car guys.....................................pump for the propper flow.

For our boating purposes it is WAY easier to just replace the seals and add spedi sleeves. Takes about 4 hours and costs about $100, and should last a long time. I have had my boat since 91 and replaced the seals once about 10 years ago without sleeve, still holding fine. Will do it again if need be. As for the oil in the crankcase, if you keep the waterpump weep hole clear any fluid leaking past the high pressure side seal (front seal) will leak out and there will be no pressure to force the coolant past the rear seal. If the hole is plugged (and some people plug them to fix the "leak") you can get coolant into the oil. Use a toothpick or wire to make sure the hole is open (lower starboard side of the pump). A lot of the things that car guys do are not very useful for boats because they tend to look for max horsepower at high RPM, while we are looking for max torque at low (300-4400) RPM.