Water pump leak?

PutMeOnTheWater · Tuesday at 4:47 PM

I’m sitting here scraping old gasket off to replace this thermostat and realized it didn’t even have a thermostat in there. So it definitely wasn’t stuck closed!

ESGWheel · Tuesday at 5:15 PM

Oh wow! So going to need some history here. Is this a new to you boat, etc.? Since you have owned it have you been out and running around with no issue until you noticed this leak? Need to know all as there may be damage to the exhaust system components due to lack of sufficient water flow. My understanding is that the t-stat provides (even when fully open) enough flow restriction to divert the needed water to the exhaust. This is not good.

PutMeOnTheWater · Tuesday at 5:21 PM

ESGWheel said:
Oh wow! So going to need some history here. Is this a new to you boat, etc.? Since you have owned it have you been out and running around with no issue until you noticed this leak? Need to know all as there may be damage to the exhaust system components due to lack of sufficient water flow. My understanding is that the t-stat provides (even when fully open) enough flow restriction to divert the needed water to the exhaust. This is not good.

New to me, yes. I’ve taken it out 3-4 times. I ran about 3/4 of a tank of gas through it since I got it. I didn’t notice any temp issues before (although I could have missed it). One thing of note is that one of the exhaust (manifolds?) has JB weld on it and I did notice it leaking once around the hose clamp in the picture. I tightened it up and it stopped leaking.

PutMeOnTheWater · Tuesday at 5:23 PM

This is what it the flow looked like when I was running it the other night, after I changed the raw water pump.

PutMeOnTheWater · Tuesday at 5:24 PM

I hooked the garden hose up to each hose that runs to the exhaust and water flowed out of the back the boat on both.

ESGWheel · Tuesday at 5:55 PM

My understanding of how these water systems work on marine engines translates into:

The temp gauge would not register an overheat (more likely under normal) but your exhaust system would be cooking with no t-stat installed.
I would suspect the JB weld on the exhaust pipe is due to the prior owner mismanaging an overheating situation and thus cracked that pipe. I’ll bet those rubber connectors are new as the old ones may have melted.
A though inspection to determine the health of this motor as well as the original root cause that motivated the prior owner to pull out the t-stat is needed.

I am out of my depth with this one in terms of what running a motor without the t-stat installed would do to a motor. Need help.

@Scott Danforth can you please provide some guidance / suggestions?. Thanks.

Scott Danforth · Wednesday at 7:14 AM

do not run a boat motor without a thermostat. the thermostat is operated as a mixing valve to regulate flow to the exhaust manifolds

PutMeOnTheWater said:
One thing of note is that one of the exhaust (manifolds?) has JB weld on it

big red flag. look for other evidence of freeze damage to the manifolds themselves as well as the motor.

ESGWheel · Wednesday at 6:30 PM

Barring other input below are my suggestions. Being unaware of your skills and what tools you have, I will default that you are well knowledgeable and equipped. However, if there is any question on ‘how to’ or what tools are needed, please do not hesitate to ask. As a precursor suggest having the following gaskets in hand prior to starting: exhaust manifolds, risers and valve covers. Idea here is after these items coming off and no issues found, they can go right back together. One tool, that is not generally in tool boxes, is a radiator hose removal tool, link. These are handy little devices that make the job of pulling off hoses so much easier, like those large exhaust hoses. Note: my suggestions are based on the assumption your engine underwent an overheat (or freeze) that was not properly tended to.

Do compression test > note if anything other than good, stop here. Post results.
Take pics (and post) of spark plugs keeping their cylinder nos. in tack.
Remove and inspect exhaust manifolds and risers. Take lots of pictures and post.
Look around the motor looking for indications of water seepage and cracks.

BRICH1260 · Thursday at 7:17 AM

It`s not advisable to run the engine with the drive in the up position. Very hard on the U joints.

PutMeOnTheWater · Friday at 1:42 PM

BRICH1260 said:
It`s not advisable to run the engine with the drive in the up position. Very hard on the U joints.

Had not heard that before! I will take that advice going forward. Thanks

PutMeOnTheWater · Friday at 1:46 PM

ESGWheel said:
Barring other input below are my suggestions. Being unaware of your skills and what tools you have, I will default that you are well knowledgeable and equipped. However, if there is any question on ‘how to’ or what tools are needed, please do not hesitate to ask. As a precursor suggest having the following gaskets in hand prior to starting: exhaust manifolds, risers and valve covers. Idea here is after these items coming off and no issues found, they can go right back together. One tool, that is not generally in tool boxes, is a radiator hose removal tool, link. These are handy little devices that make the job of pulling off hoses so much easier, like those large exhaust hoses. Note: my suggestions are based on the assumption your engine underwent an overheat (or freeze) that was not properly tended to.

Do compression test > note if anything other than good, stop here. Post results.

Take pics (and post) of spark plugs keeping their cylinder nos. in tack.

Remove and inspect exhaust manifolds and risers. Take lots of pictures and post.

Look around the motor looking for indications of water seepage and cracks.

I will do. I’m decently skilled with the right guidance and my neighbor has or has access to most of this. He suggested doing a leak down test and also suggested just pulling the motor and leaving it in the garage over winter so we can take apart and access any damage. Question 1, is there any reason to go ahead and install the thermostat and try running it again to see if the overheating problem is solved with the thermostat actually in there (I don’t know why this would be the case, makes no sense that it would).
Question 2, do you think it’s worth pulling the motor or should I try the other stuff you listed above first? I’m not sure what extra stuff pulling the motor entails like how difficult it is to disconnect from the drive.

ESGWheel · Friday at 4:00 PM

You are lucky to have a helpful neighbor. But let’s walk before running. I.e. no reason to dive in deep and pull the motor from the get go. Also, a leak down test is only needed if you have low compression. And it only provides an indication of where the issue is (rings, valves, head gasket or combination).

My suggestions are:

Put back in the t-stat so you can run the motor but only to warm it up for the compression test. In fact, I would run the compression test cold, put in the plugs, fire it up, warm it up (10 to 15 min unless you see an issue) and the pull plugs and do that warm compression test. Recall that best to disable spark when doing the c-test.
Once cooled down, pull apart, inspect and post pics, results as suggested in post #28.

Then if issues found can make the decision to pull motor and make a fun winter project out of it.

PutMeOnTheWater · 2025-10-12T12:18:47-0600

I never thought to ask this but should water be coming out of the exhaust or just from the base of the drive unit? I’m unclear how this works. It’s currently only coming from the base of the drive.

Bt Doctur · 2025-10-12T12:25:15-0600

never grease or oil on those types of rubber products, use K-Y products

Jeff J · 2025-10-12T13:19:59-0600

You should get water out the exhaust. Not sure about anywhere else because I always use a run tank. I hadn’t seen one as bad as in the video but that may be because it is trimmed up.

PutMeOnTheWater · 2025-10-12T16:25:00-0600

ESGWheel said:
Barring other input below are my suggestions. Being unaware of your skills and what tools you have, I will default that you are well knowledgeable and equipped. However, if there is any question on ‘how to’ or what tools are needed, please do not hesitate to ask. As a precursor suggest having the following gaskets in hand prior to starting: exhaust manifolds, risers and valve covers. Idea here is after these items coming off and no issues found, they can go right back together. One tool, that is not generally in tool boxes, is a radiator hose removal tool, link. These are handy little devices that make the job of pulling off hoses so much easier, like those large exhaust hoses. Note: my suggestions are based on the assumption your engine underwent an overheat (or freeze) that was not properly tended to.

Do compression test > note if anything other than good, stop here. Post results.

Take pics (and post) of spark plugs keeping their cylinder nos. in tack.

Remove and inspect exhaust manifolds and risers. Take lots of pictures and post.

Look around the motor looking for indications of water seepage and cracks.

Okay I pulled the exhaust and took pictures. Looks like the starboard side (the side that has the JB weld on the exhaust pipe) has some evidence of getting too hot. Didn’t find any cracks or anything crazy. Looks a little rusty in there on both sides. These are the port side pics. I’ll put the other ones in a diff post to keep separated.

PutMeOnTheWater · 2025-10-12T16:27:04-0600

These are starboard side pics. Let me know if more/better pics of anything would be helpful.

PutMeOnTheWater · 2025-10-12T16:33:01-0600

I’m not sure if I go some water down into a couple of the cylinders when I removed the manifolds, but 1 cylinder on each side had some water in there. I dried them with a rag. Figured I should mention it. That’s what one of the pictures above is.

Also worth noting, in earlier comments I was referring to JB weld on one of the manifolds but I was calling it the wrong thing, it’s actually on the exhaust pipe.

ESGWheel · 2025-10-12T17:35:03-0600

Compression test?

PutMeOnTheWater · 2025-10-12T19:24:53-0600

ESGWheel said:
Compression test?

yes. Main find - Removed the plug for #4, water poured out. This was cold compression test as I had already removed the exhaust.

1 180
3 170
5 178
2 186
4 1st attempt 250 and shooting water. 2nd attempt 210 and still wet
6 182

Water pump leak?

Seaman

Master Chief Petty Officer

Seaman

Attachments

Seaman

Attachments

Seaman

Master Chief Petty Officer

Grumpy Vintage Moderator still playing with boats

Master Chief Petty Officer

Lieutenant

Seaman

Seaman

Master Chief Petty Officer

Seaman

Supreme Mariner

Petty Officer 1st Class

Seaman

Attachments

Seaman

Attachments

Seaman

Master Chief Petty Officer

Seaman

Attachments