Mercruiser 250 Temp Water flow Question

[i_build]

Just got a new (used) alpha 1 out drive and the impeller was missing fins so I swapped out the pump lower and upper housing and impeller. The boat was sitting for about 4 months on the trailer before I got the newer drive. Took her out and after running on a plane for about 10 mins she gets up to 180*. She was staying at 165* before I put the new drive in.

I disconnected the feed hose that goes to my engine from the drive and I have a strong flow with the engine idling. What "strong flow" means to me... is it seems like I have the same pressure as my garden hose. At idle she stays cool consistently and after 5 minutes throttling back from hitting 180* she cools down to 165*. New manifold also installed 3 months prior to the original drive failing. I did not change the riser but she ran 3 months at 165* before the drive went bad even for long runs on a plane.

Is it possible that 4 months of inactivity could have degraded the riser? Is there more of a definitive way of me testing the flow coming from the drive to know that it is right? The problem only shows after running on a plane at about 3600 rpm after 10 mins... not sure if she would climb in temp any higher. Would like to rule out any possible issue with the supply coming from the drive before I start throwing money at the riser or circulating pump... Just don't know how to test that supply from the drive to get a definitive result (other than my visual judgement of the water coming out the end of the hose).

Please let me know if possible. I can make video if that will help.

Raw water cooled in the Gulf of Mexico.

Thank you in advance.

 

[achris]

Exhaust bits don't like sitting around doing nothing. Manifolds and elbows build up rust faster, especially flaky rust, when sitting doing nothing...

How old is the elbow? Much more than 4 years with long periods of sitting is enough to cause them to clog....

The way to test the drive water output is as follows....

https://www.google.com/url?sa=t&rct=...xLJkyJclvLTmqh

 

[i_build]

Awesome test. Thank you!

And I am pretty sure the elbow is above the 4 year mark. Priced the elbow at about 180$ provided the test works out well... will get the elbow first.

 

[crazy charlie]

Replace the tstat.clean /check the check balls in the tstat housing.pull the riser and poke through all passages with a coat hanger if anything looks crusty which can easily be the case.make sure you used the correct riser gasket without gobbs of sealant.dont use any sealany.my point is to start looking at the easy stuff first without investing any money yet.backfulsh the powersteering cooler.

 

[achris]

Replace the tstat.clean /check the check balls in the tstat housing.pull the riser and poke through all passages with a coat hanger if anything looks crusty which can easily be the case.make sure you used the correct riser gasket without gobbs of sealant.dont use any sealany.my point is to start looking at the easy stuff first without investing any money yet.backfulsh the powersteering cooler.

No check balls, no power steering cooler. It's a MC-1 inline 6, 165....

If the engine temp is good up until the engine is over 3,500rpm, then starts getting hotter... On those engines, that a classic blocked elbow...

 

[i_build]

Thank you for your help. achris it's crazy that I didn't know who you were up until I saw some of your videos and most of them I had already watched even before I saw your 'my videos' links. Thanks for all of your help and videos.

Was there any reason why you gave up on the 165? Was it just beyond rebuilding or were there other reasons. I have seen a number of posts that say the 165 inline 6 is a reliable engine.

 

[achris]

...Was there any reason why you gave up on the 165? Was it just beyond rebuilding or were there other reasons. I have seen a number of posts that say the 165 inline 6 is a reliable engine.

I had rebuilt the engine and it was running very well. One problem was the gimbal housing, too much corrosion. And the drive had a cracked gear in the top housing. The options were to try to find a good second hand MC-1 gimbal housing, and in 1994, that put them all at 14 years or older, and 99% of boats in Australia as salt-water, so that wasn't looking too good. The other option was to sell the boat and buy something with a newer engine... So we (wife and I) looked at how much we'd get for the Bertram, how much a new engine package would be and looked at what was available for that money... Not much really. Just be buying as many problems as we already had, and in an inferior hull.... So, out with the 165, in with a brand new 4.3LX, and sell the 165. Best decision we ever made....

The 165 is a reliable engine, but for it's capacity, it's not a great producer. 4.1 litres making 165hp... the 4.3 makes 205 without vortec heads, almost 230 with, and uses far less fuel doing it..... Apples and oranges. And the 4.3 is just as reliable, and doesn't develop that horrible small end knock the 165 is infamous for.

Hope that answers the question.

Chris........

 

[i_build]

Got the new riser and installed it. At the dock I let her sit at 2500 rpm for about 10 minutes and the temp did not go past 165*... Was Happy... Then I dropped her back to and idle for about 5 minutes and just before I was getting ready to put her back on the lift I just brought her up to 3200 RPM for about 10 minutes... She hit 180* unfortunately... really discouraging.

I have not done the flow test in the manual you provided... I don't know if pieces of the original impeller from my replacement drive might have made there way up into my cooling system somewhere. It was a used drive that I wanted to make sure shifted and worked before putting in a new pump. Little did I know the impeller would only have 1 fin left in tact. I did find 1 fin lodged in the lower portion of the pump and hope that the rest made it through the drives prior owners cooling system.

Will get some measuring containers and do the flow test next... I really don't think it is the flow as it gushes out of the line at my homes garden hose pressure... as opposed to how I witnessed my original drives bad impeller water pressure before I replaced that pump... but will confirm via the test.

BTW the manifold is half a season old, riser (brand new), Impeller and pump lower and upper portions are brand new. Only thing I think left to replace is the circulating pump.

Please let me know if you have any suggestions... It's just really odd that besides sitting for 4 months, the only thing I changed was the drive and now I have cooling problems. Before that... reliable 165* rock steady after running on a plane for long periods.

 

[kenny nunez]

If there is no pieces of the impeller causing a blockage and the water pump is fresh,here are a few other suggestions. Are you sure that the gaskets on either side of the stainless water pump plate are not reversed?
A quick water test is to first warm up the engine, turn it off then remove the hose from the drive pump at the thermostat housing, start the engine and point it Into a bucket then try to stop the flow with your thumb or the palm of your hand. If you can stop it then either the plastic water pocket is melted or the hose from the bell housing to the gimbal housing is leaking.
If that is in good order remove the circulating pump to check if the impeller is not rusted away or slipping on the shaft.
It may also be possible that @ 3200 rpm at the dock you were picking up exhaust bubbles into the pump suction which will create a steam pocket around the sending unit and there is no problem so take it for a cruise to be sure.
Another check is to replace the hose from the thermostat to the manifold with a clear one, if you get bubbles at that point it will be a combustion gas leak, since the engine is rebuilt most likely that will not happen but it is just another test.
These are some of the things I encountered in my 35+ years at my shop.

 

[i_build]

Thanks Kenny... Tomorrow it's raining all day down here in 'Sunny' Saint Petersburg FL... will see if I can sneak in the tests if there is a break in the rain and post back.

 

[kenny nunez]

That rain is sure playing havoc with the 24 Hours of Daytona!

 

[Lou C]

If the boat was ever docked or moored in salt water then you can have marine growth inside the drive water intakes and water passage. I had this problem with my Cobra and had to split the drive and clean out that area to solve a mild overheat. I wound up removing the water intake screen and left it out because I had a chronic problem with barnacles growing in it for several years. Now I can rod out the water intake holes as needed.

 

[i_build]

The replacement alpha 1 drive I just installed was a freshwater only drive.Very clean inside and out besides the old impeller.

 

[i_build]

Here is a youtube video of me attempting to stop the pressure with my thumb. Since this is kind of a judgement call measurement could you take a look and let me know. I could not stop it completely with my thumb. This was at idle.

Chris that noise in the background is as you mentioned with the inline 6's. I tried adjusting the valves but I think I have a stuck lifter in there. It goes away and comes back and would have to be singing while I made this video.

https://youtu.be/-4kpK83kfuI

Thanks in advance.

 

[kenny nunez]

It looks like you have good pressure. I do not remember what the volume per minute is so maybe Chris has that information. I also once encountered the large hose from circulating water pump collapsed on the inside and not letting the water circulate, just another thing to check. Is the small bypass port clear inside of the thermostat housing? Is your circulating pump the original style with the cast iron impeller? If it was replaced with a stamped steel impeller style it may be rusted away.
On the lifters, I always turned the nut down no more than 3/4 of a turn from “0” clearance without the engine running. Remove the spark plugs and turn the engine by hand and watch if any of the rocker arms are out of adjustment.

 

[achris]

... and just before I was getting ready to put her back on the lift I just brought her up to 3200 RPM for about 10 minutes... She hit 180* unfortunately... really discouraging.....

Are you doing this in neutral? If so, there may be the problem. Does it do it when you're running in gear?

Chris.....

 

[i_build]

Prior to the riser change the overheat occurred on a plane. Testing the riser install I was at the dock in neutral. Sounds like I need to take her out for a cruise to test properly?

 

[achris]

Yes. Can't run in neutral at that speed because the water pump isn't being fed water and it can't just suck enough in. Have a look at the intakes, they are shaped so water is fed up to the pump as the drive moves through the water...

 

[i_build]

Took her out and she got to 180*. Came right back to the dock at idle and she cooled off. Pulled the thermostat housing and found the issue. Those pieces of the impeller jammed themselves up into the narrowest part of the housing. I removed those chunks and now she holds at a little less than 160* at WOT for 10 mins and probably more but that's what I ran today. I know I needed the riser anyway as that was one of the original parts to the cooling system and I was not sure how old it was. Thanks guys for all of your help. Might be able to go catch some grouper now.

 

[kenny nunez]

Were the pieces stuck in the small by-pass port? Glad to to hear that you was able to find the problem.
When I first bought my Donzi the engine driven pump was burned up and I could only find 4 of the impeller pieces, I took every hose off and the thermostat housing, I never could find the rest, I guess they are in the lower section of the block.