Closed Cooling System on Port Engine Running Hot(ter)

[achris]

Having been a mechanic in the pleasure boat industry for many years, stay with the I/Os. Outboards of 'yesteryear' were a lot easier to work on, yes. Modern outboards, especially the 4 strokes, are as much a pain to work on as the I/Os, but you don't have the luxury of buying 'off the shelf' parts for them. If the IAC on an outboard dies, you have only one place to buy it, the OEM... And they make you pay for that privilege... No rushing off to autozone with an outboard....

Chris....

 

[HT32BSX115]

Having been a mechanic in the pleasure boat industry for many years, stay with the I/Os. Outboards of 'yesteryear' were a lot easier to work on, yes. Modern outboards, especially the 4 strokes, are as much a pain to work on as the I/Os, but you don't have the luxury of buying 'off the shelf' parts for them. If the IAC on an outboard dies, you have only one place to buy it, the OEM... And they make you pay for that privilege... No rushing off to autozone with an outboard....

Chris....

Yeah. And I think this problem is going to turn out to be something simple too.....

 

[tpenfield]

Well, if the truth be told . . . my brother hit a rock with his outboard this past weekend . . . we fixed it with duct tape

 

[Lou C]

Whenever I get tired of working on the I/O and think I want a modern outboard I look at the price of Yamaha parts; that usually convinces me to stick with what I have!
Getting back to the problem, I wondered if the hotter engine might have had more internal corrosion thereby slowing hear transfer? The engines were run a long time in lake water but raw water cooled. Still you can have some corrosion. I wonder if chemically ckeaning the block & heads might help.....

 

[tpenfield]

Yes, my heart is not set on the lean condition/fuel rail pressure being the cause of the overheat. . . it may be something real simple like you mentioned. I do have a sense of urgency about the lean condition, as it can lead to bigger issues. So, for me it is a matter of fixing the issues that I find and working from there.

I have thought about sediment or rust scale inside the engine block (however, the engine block looks really good from what I can see so far). If the fuel pressure issue does not pan out, then I am headed in that direction though.

Another tidbit that I may not have mentioned is that I took off the exhaust tube that connects the elbow to the y-pipe in order to expose the exhaust flappers. I only did this on the port side cylinder bank (port engine), still need to get to the starboard side bank. 1/2 of the flapper is missing :noidea: . . . so I was thinking that it may be lodged somewhere further down the y-pipe, etc.

Thinking that an exhaust restriction could cause the same sort of overheat problem, I took my inspection camera and snaked it down the y-pipe as far as it would go to see if there were signs of the flapper remains down there. None that I could find . . . I do have the exhaust 'tubes' rather than the 'bellows' on the transom assemblies, so the flapper could have been ejected entirely. It seems like the flappers are only good for a few years. Maybe I should get new ones at this point, just so I have functioning flappers.

Anyway, exhaust restriction is just another possibility that I have been considering.

Longer term, I do want to get a boat that can handle the slop a bit better . . . but maybe I could stick with an I/O setup. I do have dreams about twin Mercury Verado's and the super charger 'whine' bringing a boat up on plane in about 2 seconds. Might stretch the boat budget though . . .

 

[achris]

....Thinking that an exhaust restriction could cause the same sort of overheat problem, ...

Not at idle.

 

[nola mike]

Somewhat off topic, but how do the electronics determine a lean condition? In a car you're running closed loop with feedback from the o2 sensor(s). Do you have them on the fi boat engines?

 

[tpenfield]

I know that my engines, having the MEFI-1 controllers, do not have O2 sensors. Some of the latest versions of controllers may have them. :noidea:

I wondered the same thing about the controller data from the Diacom software. The "Fuel Mixture Status" indicated 'Lean' . . . I wonder if it is getting that directly from the ECU or calculating it based on the individual pieces of data, such as RPM, Injector Pulse, Manifold Pressure, etc. :noidea:

 

[nola mike]

I was wondering if you were in fact running lean. The ecu can guess at what the mixture should be (and adjust fuel delivery accordingly), but without measuring downstream gasses how can it say it's lean? And for that matter, if it does think it's lean, why doesn't it compensate by increasing fuel delivery? Bear with me as I'm now doing car diagnostics, and I'm not sure how well it translates to marine efi. Normally if a lean condition is detected, the ecu compensates by a combo of limiting air intake and upping fuel delivery. That shows up as "fuel trim" on a scan tool, and corresponds to a deviation from ideal a/f mixture. If it gets far enough away from ideal, it triggers a check engine light. In your system I don't see how it could compare actual v. Ideal. But still, before signaling lean I would think that the ecu would have to be outside of what it considers a normal fuel delivery v a given Maf. A wide band o2 sensor in your exhaust could tell you your mixture directly. Again, I don't know if there's anything comparable in the marine world.

 

[HT32BSX115]

A wide band o2 sensor in your exhaust could tell you your mixture directly. Again, I don't know if there's anything comparable in the marine world.

Something tells me that the newest marine engines ARE closed loop partly because they have "cat" convertors.....

I do have dreams about twin Mercury Verado's and the super charger 'whine' bringing a boat up on plane in about 2 seconds.

Might stretch the boat budget though . . .

I think it would be cheaper to pull those 454's and bolt in bored/stroked 454's or built up 496's!

1/2 of the flapper is missing

. . . so I was thinking that it may be lodged somewhere further down the y-pipe, etc.

Haven't we had more than a few people here have overheats due to obstructions in the exhaust y-pipe?

 

[tpenfield]

I was wondering if you were in fact running lean. The ecu can guess at what the mixture should be (and adjust fuel delivery accordingly), but without measuring downstream gasses how can it say it's lean?

The only thing that really pointed to a lean burn was when I originally looked at the spark plugs. They were definitely running lean. I think that this engine used to run rich a few years ago . . . so much that it had carbon build-up. Looks like that issue is solved

I got the Diacom software to try to further diagnose the lean burning condition and compare it to the 'good' engine (starboard engine). The Diacom did not show any codes or significant operating differences between the engines, so that was somewhat of a dead end. The controllers are the first generation of the MEFI and do not have much sophistication and certainly don't compare to current day automotive ECU's.

What seemed to confirm, or at least correlate, to the lean condition was that the fuel pressure regulator on the port engine was about 20% out of spec. The starboard engine was right at the lower end of the spec (34 psi)

Since then, I have been waiting for Mercruiser parts to arrive, as the after market parts were NG. It seems that all of the fussing and fixing that I have done so far has improved the port engine at cruising speeds, as it does not seem to go above 170, where it used to go to 180, but the idle temp is still alarmingly high (165-167)versus the starboard engine (148-150). . . that symptom may be pointing to a coolant circulation problem.

More to come once my new parts arrive.

 

[Lou C]

"I got a new thermostat and tested it on the stove. Starts to open at 160 F and wide open at 170 F
but the idle temp is still alarmingly high (165-167)versus the starboard engine (148-150)"

...after I read your 2 statements above, I started thinking.....

Ted, I read through all of this again, and here's my question. If your stat's are 160 units, and start to open at 160 and are fully open at 170, why then do you feel that the idle temp of 165-167 is alarmingly high? It really should be that high based on how the 'stat is behaving. I think it may be that your other engine might be idling cooler than normal...perhaps that stat, is not closing all the way as it should....
On my '88 OMC, raw water cooled, it came with a 160 stat. I've tested a few of these, the exact same way as you did with that same thermometer! And they usually opened a little sooner than yours. However, I'd like to see a test between both of your stats, in the same pot of water. My engine never idles lower than 160, usually between 160-165. If it runs cooler, (120-140) that is a sign that the stat is starting to stick or there may be a grain of sand or flake of rust keeping it from closing. The only time I get a reading of less than the stat's rated temp when all is right, is sometimes right after getting on plane, it will drop slightly below 160 but will stabilize at 160-165. Then if I slow down, to idle after coming off plane, it will rise briefly to 175 and then cool back down to 160-165. Always been this way.

 

[captkevin]

Lou i had the same thought. If the thermostats 160 degrees is the starboard engine running too cool at 148-150?

 

[HT32BSX115]

Lou i had the same thought. If the thermostats 160 degrees is the starboard engine running too cool at 148-150?

I didn't look back through the posts......but I think he swapped T-stats didn't he?

 

[Lou C]

The other thing I thought of was that Ted drilled holes in the stats to increase flow but this could have the effect of the engine temp stabilizing at a lower temp than the rated temp of the stat.
Not sure if the stats were switched side to side.

 

[achris]

So why is the port engine taking longer to 'cool off' after a run?

 

[tpenfield]

Just to clarify . . . yes I drilled a few (3) 1/4" holes in the t-stats to provide some by-pass during warm-up. I did this because there did not seem to be enough by-pass within the system prior to the engines reaching operating temperature (which is about 10 minutes for a cold engine under no load) during this time the coolant in the exhaust manifolds did not get hardly any flow and would get very hot. Once the t-stats did open, allowing full system flow, the very hot coolant would flow into the engine causing fairly dramatic temperature swings. As soon as I drilled the holes, the temperature rose during warm-up in a steady and consistent manner.

These holes are not enough to cool the engine under load, I replaced the t-stat on the port engine early on in the process, and also drilled 3 holes, they are a bit smaller maybe 3/16". I also tested the new and old t-stats for the port engine. The new one before going into the engine and the old one after it came out of the engine. Both started to open at 160 F and were wide open by 170 F.

Keep in mind that over the 4 years of operation with the closed cooling systems I got;

Years 1-2: Both engines 155-165 all day long.
Year 3: Port 165-175 and a longer recovery time. Starboard 155-165 all day long.
Year 4: (this year) Port 170-180 and longer recovery time. Starboard 155-165 all day long.
After fussing and fixing, the Port seems to stay at 170 and still has a longer recovery time.

 

[tpenfield]

DRAMA ALERT, DRAMA ALERT !!! :violin:

So, I sent the aftermarket fuel pressure regulators back to the eBay seller after having tested them per the procedure in the Mercruiser Manual #16, pages 5C-61 & 5C-63, which call for the ignition to be turned on for 2 seconds and observe the pressure gauge connected to the schrader valve.

Pressure is supposed to be 34-38 psi and holding. My original regulator on the port engine was 30 psi. The starboard engine was 34 psi.

Neither of the new regulators would pass this test. One regulator would hold at about 25-28 psi and the other regulator did the same but would loose pressure after about 3 more seconds. I further tested on a bench using air pressure and niether would hold 34 psi and one leaked air constantly regardless of the pressure.

So, I sent them back to the eBay seller, who tested tested them (not sure of the procedure he used). He has refunded my payment, but also let me know that the regulators tested at 35 and 33 psi, and that I needed to refer to the Service Bulletins on the regulators to get a proper test.

Well, I looked for service bulletins on these regulators and the VST system in general, and have not found anything that supersedes the testing process in the manual. Can you guys point me in the right direction on any service bulletins. :hail: The seller also asked early on in our dialog if I had tested the regulators while the engine was running, (which I am not really able to since I have to remove the intake plenum to get to the schrader valve. My understanding is that with the engine running the pressure should be 37-43 psi (higher than the static testing of 34-38 psi).

Not that it is a big deal, since I got refunded the $$$, but I would like to fully understand the regulator testing and any service bulletins, so when my Mercruiser OEM parts arrive, I can be sure to test them correctly, etc.

BTW - I did try the 'eBay' regulator in the engine and the engine seemed to quickly heat up faster than I had ever seen it, to a point where I felt it wise to shut it down. :facepalm:

 

[Lou C]

While the holes are too small to cool the engine I was thinking that they could have an effect similar to a stat that does not close all the way with lower than expected temps at idle. Why not call the company that sold you the closed cooling kits and see if you can talk to a tech guy and see what they think.

 

[tpenfield]

While the holes are too small to cool the engine I was thinking that they could have an effect similar to a stat that does not close all the way with lower than expected temps at idle. Why not call the company that sold you the closed cooling kits and see if you can talk to a tech guy and see what they think.

Hi Lou,

Not an issue really. I think HT (Rick) and I discussed the t-stats a bit way back when I installed then, as he has the same kit. More my preference than an absolute requirement. My thoughts are that with the by-pass holes, the t-stat will tend to open less to regulate the temperature. . . the engines worked fine with them that way and the starboard engine still works fine.

Any help of the pressure testing for the fuel regulator? I have yet to find a service bulletin that outlines a different procedure than the manual has :noidea:

the Manual says 34-38 psi with just the ignition turned on . . . but it seems that we have kicked around 37-43 psi as the spec. pressure . . . wondering if that is while the engine is running and getting the vacuum assist :noidea: I'll keep digging, but if someone can point it out in short order that would be helpful. Thx.