98 Johnson 225 Temp Alarm / Overheating

[Bergertime]

Ok all the saga continues....  Left work a little early today and pulled the boat back to my house to start the work.  Here is what I encountered:

1) Before any mechanical work I put muffs on (duel feed model - Thanks Flounderpounder225) and started her up.  She fired right up and sounded normal but no water came out the pee hole or the vents above the cavitation plate.  I let her run (2-3 minutes) until the head was hot to the point where it was uncomfortable to keep my fingers on it for more than 6-8 seconds.  After no water flow and the increasing temperature I shut her down and re-attached the hose to the hose port to aid in cooling with the engine off.

2) I changed both t-stats and gaskets with no trouble.  The ones that I removed has some mild corrosion on them and a small piece of see weed.  However, a bath in boiling water after the fact resulted in the tops popping out as I suspect they should when working normally..  Anyway - have a couple extras now. :)

3) Ran the motor in the same manor as above with the same result.  No pee stream and no water from cavitation plate vents, increasing head temp started to make me nervous so I again shut her down.  

Based on the above I now suspect a water pump issue as some have suggested however I am still perplexed as I did observe a strong pee stream even when engine was running in safe mode back to the dock last Sunday.  I guess I still have question on engine water flow when on muffs vs. submersion.  Anyway - I have a mechanic coming by on Monday for some other stuff so I am going to have him pull the lower unit and check impeller etc.  I did not have any way to run the engine from a garbage can (mine will not hold water) but after the mechanic looks at it on Monday I will drop her in the river and test her out.  Just kinda weird I guess...  Thoughts?

I really had high hopes the t-stats were going to resolve...  Any new thoughts you all may have after today's developments

[wingtime]

I kind of suspected your water pump was either installed wrong or running it on the flush port melted it.  Running it on the flush port does not make sense to me.  I believe the water flow is in reverse when using the port.  So anything the pump tries to push up to the powerhead would just be pushing against the hose pressure trying to flow down.  The pumps will always pump better while in the water vs the muffs.  You should have water at the pee hole after say 30 seconds on a OMC shut her down.  If you had a Merc you would have to wait for the T-stats to open.

[dburr]

Drop the lower unit and open up the water pump and unless the uptake tube is plugged you will most likely find a glob of rubber/melted plastic where the impeller was or maybe the whole inner housing has spun..

[fitz73222]

Wing and deburr are correct with their analysis and summary. The waterpump has been damaged because of the earlier flush method. I'll give a brief description of how the cooling system works. First you will notice that the "tell tale" (pee water) is sourced from a lower point in the block in most cases from the exhaust plate between the cylinder heads. The typical cooling system gets the water from the pump into the exhaust portion of the block first. This is because the dry exhaust coming from the exhaust ports gets hot instantly as soon as the engine lights off. There is a baffle plate that separates the incoming cooling water from the pump and the dry exhaust. The water shield created on the outside of the plate, cools the dry exhaust temperature buy absorbing the heat generated. The tell tale outlet lets you know the water pump is working or not in this case. The block continues to fill until it reaches the cylinder heads at the thermostats. Small bypass water also fills the cylinder heads on the opposite side of the thermostat to prevent thermal shock when the thermostats begin to open. The thermostats essentially interrupt the water flow by limiting the flow until the thermostats reach operating temperature and begin to open and allow the warmed water to begin circulating through the block and head passages. This is when you will begin to see hot water start exit the vents above the anti-ventilation plate in the gearcase. Depending on outside air temperature this water will appear hot and steamy but is no where near 212 degrees; its just the difference between ambient temperature and the 120 +/- degree water exiting the the block. The thermostats will continue to feather the water in the block to maintain operating temperature. You may actually see the water flow reduce and increase out of the gearcase vents as the thermostats do their job. Additionally, most outboards use a secondary pressure control device sometimes known as a poppet valve to control water pressure at high speed that keeps the water from running through the block too fast that would otherwise not allow for good thermal transfer of the hot combustion temperatures into the flowing cooling water. So if you have a high speed overheat condition it's usually the the pressure control valve(s). Your engine may actually pump water when submerged but the efficiency has been compromised because of loss of contact between the impeller, baseplate, and housing. You should see transfer of rubber to the metal components. Purchase a new complete waterpump kit and replace everything. This should get you back to square one. Also make sure if the rubber impeller is missing portions of the vain (rubber paddles) you must account for all of the pieces to make sure no pieces are lodged in the water tube or in the powerhead base that could cause restricted waterflow. So lesson learned; run her on muffs to flush or use the flush port without running the engine. I think you'll be good to go from here so let us know the outcome.

[dburr]

Fitz, OUTSTANDING description sir!!!    

[Bergertime]

Well all.. I have some good news to report! My overheating problem has been resolved but it was a journey to get there... However, first off, I would like to thank all the folks that replied to my first post.  Your advice and insight was truly appreciated and as a first time boat owner I can't say enough on how valuable it was.

Here it goes...

Saturday - I replaced the thermostats that evening in hopes I could take my boat out on Sunday but after a quick swap out (very easy replacement btw) and a run on muffs (the dual feed model - Thanks flounderpounder225) my engine quickly heated up beyond the point where I could hold my fingers on the head for more that 5-6 seconds and I never received any water out the cavitation plate vents so I quickly shut her down.  Problem not solved by t-stat replacements but good maintenance anyway.

At this point I had a different marine mechanic already scheduled for Monday to do some non related work so I called him and gave him the heads up on the cooling issue which would now take higher priority vs. the original work I had planned.

Monday - Marine Mechanic showed up on time ready to work.  Throughout the day I was impressed with him so if you would like a referral and you live in the Tampa Bay area please PM me.  Although I don't have a long history with him I was impressed with his work and attention to detail.  Anyway, we started to work on the cooling issue and I showed him the problem again with muffs and his digital laser thermo indicated head temp quickly approaching 200 degrees.  Shut her down again. The steps to the diagnosis and the fix....

1)Pulled the lower unit and visually inspected the current impeller which was recently changed 3 weeks ago, yielded no clues.  Impeller was in great condition.

2)Pulled t-stat housings off and t-stats out and ran the motor.  No water coming out at the top but some coming out of the pee hole.  

3)Mechanic feared that the heads were severely salted preventing water flow as indicated by water coming out of the pee hole but not making it up to the top of the head.  Started to pull the head covers off.

4)Quickly found two head gaskets after several attempts at local part shops.  While in Marine Mechanic shop all three guys there were confident that it was a water pump issue and convinced me to replace the whole thing with a new kit since the prior swap-out was impeller only.  At this point I was willing to try anything especially a new water pump unit which is not extremely expensive and good maintenance anyway. Additional purchase.. now up to $200 in parts.

5)Taking of the head cover off yielded a moderate salting issue but more importantly uncovered two very close to failing head gaskets with a couple spots that were likely to develop into holes very soon.  Kinda some good karma there.  Mechanic cleaned the salt out of the head and remounted the covers.  Now on to the new water pump install.

6)Replaced the whole water pump - Here comes the culprit!  Upon inspection after the new-old impeller and pump was removed we found that the floor plate of the existing pump was concaved down towards the prop. This prevented the impeller from creating the suction and water flow needed to push the water up to the top and cool the engine properly.  When I observed the mechanic (Sunday) remove the impeller some force was needed to loosen the brass fitting which holds the impeller on which he applied horizontally to the drive shaft. The prior Mechanic (which I will never let touch my boat again) used significant downward force (hammer and screwdriver) to free the first impeller which forced the floor-plate to flex and bend downward.  This was not evident until the floor plate was pulled and inspected holding it sideways.  However, once viewed outside the pump the curvature was significant and obvious.  Lesson learned there.

7)Re-assembled the whole pump unit, re-installed the lower unit and started her again.  This time we had water flow out the t-stat housings and a pee stream that would strip paint!  

8)Put t-stat housings back in and let her run for a little more than 10min on muffs.  Outside head temp ranged from 115 to 128 degrees and stabilized there, cooling issue resolved Yay!

9)Took her out on the Bay last night with a friend for some evening fishing and she ran great with no issues.  Validation - problem solved.  Fishing was terrible though....no matter.. boat is running well!

Thanks again all!

BB

[pigbike]

Sounds like Fitz hit the nail on the head when he said to use a complete pump kit, not just a impeller. Then again the first guy (Bubba) beat on it, so who knows.  I have always heard to go the complete pump kit route.

Glad you finally have it working again.

[flounderpounder225]

Awesome outcome...   and thanks for the follow up!

[merlinroad]

For future reference my 1999 225hp Johnson operation & maintenance manual says you can run the engine from the flush port with the engine in the vertical position. If you need a copy of the manual PM me and I'll see what I can do.

John