'86 Hunter 34 coolant through exhaust

[Db421]

Just replaced my impeller (missing 3 vanes, found 1) and wondered how much water I should expect to see coming out of the exhaust. It's hard to tell from the cockpit how much is flowing out through the exhaust, If the water was warmer I'd just jump in and take a look. I can't imagine everyone with this boat jumps in the water every time they want to know if the pump is working. Amy tips?

 

[jviss]

Look up the raw water pump specs to see the flow spec at a particular RPM. Get a bucket and time how long it takes to fill it from the exhaust. Calculate the GPM, compare to spec. If there's a big difference, you might have an obstruction.

 

[Don S/V ILLusion]

If the missing two blades aren't in the pump housing, the only other place they can be is in the heat exchanger.
Regardless of the current flow rate, they can move around and block it later. Either way, you should find them.

 

[dmax]

The missing blades may also be in the hose from the pump to the heat exchanger - I found two in mine from a PO. You definitely want to find them as Don says.

 

[Capt Robbie]

not sure what the exact amount is, however it’s approximately two gallons a minute at idle. This is based on how much non toxic antifreeze is used to winterize the engine. Can’t really see the exhaust flow unless standing on the dock. Maybe if you hold a mirror on a pole you might be able to see it. I’ve kinda just been able to hear the exhaust water splash and just know by the sound that it’s ok. Unfortunately this listing technique is not going to help, however eventually you will be able to hear that it’s good.

 

[Ralph Johnstone]

If you've got a Yanmar engine, feel the mixing elbow at idle. It should be slightly warmer than hand temperature.

 

[RoyS]

Temporarily disconnect the small hose at the top of the mixing elbow and direct it to a bucket. Start the engine and watch the bucket fill. At idle I would expect the bucket to fill in about twenty seconds. The exhaust hose will not be damaged in this short test without cooling water.

 

[Db421]

Great answers guys---I definitely plan on finding the other two vanes but I just wanted to be sure of a relatively easy way to check flow. I'll put my go pro on a selfie stick for starts, then try disconnecting the small hose on the mixing elbow. I can hear water splashing and see some spitting. Also, no idiot light yet. I'd like to put a real temp gauge in but that's another issue.

Thanks!

 

[jviss]

Great answers guys---I definitely plan on finding the other two vanes but I just wanted to be sure of a relatively easy way to check flow. I'll put my go pro on a selfie stick for starts, then try disconnecting the small hose on the mixing elbow. I can hear water splashing and see some spitting. Also, no idiot light yet. I'd like to put a real temp gauge in but that's another issue.

Thanks!

One of those non-contact IR thermometers is a great tool on a boat. I got mine for about $15, as I recall. You can measure the temp of the thermostat housing, which is a good indicator.

 

[markwbird]

You should be able to see it and hear it coming out the back. It's not continuous. It "spits" every few seconds. If its not working properly the engine will overheat and you will get an alarm. Make sure the alarm is working. The pieces of the old impeller are probably lodged in the heat exchanger so you should open it up and clean it out. Also, it is very common for soot to build up in the exhaust elbow and clog it. Pull the raw water hose off where it attaches to the exhaust elbow and look to see if there is soot. If so, you can clear it with a screw driver.

 

[Tally Ho]

I can usually hear a change in the tone of the exhaust on my O’Day 322 with a Yanmar 2GM20F engine. But my exhaust is also above the waterline and easily visible from the helm.

My Hunter 280 exhaust was under water…made it hard to see ;-). But I could still hear a difference in the tone.

Greg

 

[stuendan]

Assume your motor is a 2gm20F - the manual says 422 gal/hour @ 3600 rpm or 7 gal/min. Assuming a linear relationship between revs and flow, you should be getting around 1.5 gal/min at idle (750 rpm). This checked out for me when I tested the system following an overheat after forgetting to open the cooling water seacock (I've since replaced the impellor)! To measure the flow I took the hose off between the vent loop and the exhaust bend and attached a 5/8" pvc line from the vent to my bucket, then ran the motor at idle.

My exhaust is under the water, and the note does change with and without cooling water but a flow switch in the cooling water inlet line is the best bet. I have yet to install mine but intend to use the spare alarm and light on my engine panel which is there for a sail drive leak, to alarm when there is no cooling water flow.

 

[jssailem]

Even if the exhaust is underneath the boat, most are at or very near the stern. Back the boat into a slip and check the exhaust out while standing on the dock. If looking is not enough, get in a dinghy and snug it up to the stern, lean over the side of the dinghy and feel the water.

 

[flightlead404]

Great answers guys---I definitely plan on finding the other two vanes but I just wanted to be sure of a relatively easy way to check flow. I'll put my go pro on a selfie stick for starts, then try disconnecting the small hose on the mixing elbow. I can hear water splashing and see some spitting. Also, no idiot light yet. I'd like to put a real temp gauge in but that's another issue.

Thanks!

We live in midtown (Atlantic Station) when not on our boat (returning mid April, currently on the hook in Cocoa FL). If you need help, tools, another set of eyes, or crew pm me.