Rising Engine Temps Changing Thermostat, Risers and Manifolds anything else?-gctid405703

[Guest]

I will try to make a long story short.

Boat 2252 Ciera Classic year 2000

305 Mercruiser Alpha One Gen 2 Raw Water Cooled

Starboard side riser always hotter then the port side.

Had the boat since 2004 and to my knowledge the manifolds and risers have never been changed. I planned on doing it at the end of this season but have run into temp problems. Last year I changed the water pump, this year before I put her in I changed the impellar. I have been out 2 or 3 times a week since June. The temp has always been steady at just under 170. The boat sat for a week and I decided that since I was going to Florida for a week I wanted to run her good to try and clean her bottom. Well after running for about 15 to 20 minutes at about 4000 rpms I saw the temp gauge begin to spike, it almost hit 200. I backed off the throttle and it dropped quickly. I slowly opened her up again and the gauged climbed but not as high as before but still higher than normal. I eased it back down to about 3000 rpms and she seemed to run at a steady temp but higher than normal, 175 or so. I could see the gauge flucuate when the Tstat opened and closed. At lower speeds everything pretty much seemed normal. Came back from Florida a week later and took her out today. She seemed to be running a little hot then at one point the the temp dropped like a stone, then rose a bit, then she went back to running about 175 to 180. Again when running at lower speeds all seemed normal. I am thinking that I have restricted water flow through the system. I am attributting the temp spikes to pieces of crude from the risers and or mainfolds blocking more of the passages and then freeing themselves. After I got home I spent the better part of this afternoon reading the riser and manifold threads. I read the thread about loosening the bolts while the motor is hot so I went out to give the bolts a once over. They are all easy to remove. Now I have been shopping aroung for mainfolds and risers. I found this place from one of the posts http://www.mercexhaust.com/

The prices seem very good for both the osco and the mercruiser replacements. I am going to replace the t-stat tomorrow and order the manifolds and risers. Even if the T-stat turns out to be the problem 11 years on the manifolds and risers is way past the experation date. My questions are....

1) Could I possible be missing something else that could be giving me this problem? Such as a bad guage or some form of flapper valve.

2) Are after market risers and manifolds ok to go with or shoulf I stick to OEM?

3) Does the type of gasket matter?

4) Since I will have the manifolds out what else if anything should I change? Spark plugs come to mind, anything else?

I plan on going with the plank across the gunnels and winch strap idea and using anti-sieze when I reinstall the bolts, Thanks for reading and adding any tips or suggestion.

[Guest]

The one thing you didn't say is are you in salt or fresh water.

The manifolds risers ect will last 20 plus years in fresh water maybe 5-7 in salt.

Your thermostat housing may have a balancer rod between the two sides, make sure this is not stuck.

Definitely change the thermostat 160 for fresh water 140 for salt.

This is likely your engine:

http://www.mercruiserparts.com/Show_Pictures3.asp?dnbr=884715&ivar=images/COMMON/1719.png&inbr=8182&bnbr=170&bdesc=Thermostat+and+Housing

If not find it here:

http://www.mercruiserparts.com/selectSerailRange.asp?doc_nbr=5%2E0L+CARB+ALPHA%2FBRAVO

Cheers

[Guest]

Sorry, I am in salt water. I looked in the manual and it says the t-stat is a 160.

[Guest]

It sounds like you have good plan together. In my opinion aftermarket manifolds are ok. I just put a set of Osco manifolds, risers and spacers on my 5.0. They fit like oem and I have had no issues. Spark plugs are a good idea while the manifolds are off. Take a look at the ignition wires, distributor cap, and rotor as well. If they have been on for a long time maybe it's a good time to change them too. You can get to them easily with the manifolds still installed though so you could always replace them later. Take a look at the starter. I would at least clean the connections at the starter while the manifold is off. Also take a good look at any cooling hoses feeding the risers or manifolds and replace any that look suspect. It would also be very easy to do a compression test while the manifolds are off. When installing my manifolds, I was able to hold the manifold against the cylinder head and get the bolts installed several threads at the ends of the manifolds. I was then able to slide the gasket in after the fact. The new gasket I installed had a cutout to go around each end bolt for the manifold so there was no need trying to struggle with lining up the manifolds and gaskets at the same time. I also replaced the water shutters/exhaust flappers at the same time. The starboard side was very noisy. Inspect the rubber elbow couplers and replace them and the clamps if needed.

Matt

[Guest]

kwmeyer13 wrote:
Sorry, I am in salt water. I looked in the manual and it says the t-stat is a 160.

You can suite your self, however, the T-stat may have caused your problem.

Salt starts leaching out of water at 150 and will leave deposits in your engine and cooling system.

That is why 140 is recommended for RWC engines operating in salt water.

The engine is more efficient at hotter temps so many people install FWC kits on their engines. Then only the heat exchanger sees salt water.

[Guest]

What is the exhaust/flapper thing? Is it hard to change? How do I know if I have a problem with them? Is doing a compression test hard? What tools do I need for it? Thanks

[Guest]

check737 wrote:
You can suite your self, however, the T-stat may have caused your problem.

Salt starts leaching out of water at 150 and will leave deposits in your engine and cooling system.

That is why 140 is recommended for RWC engines operating in salt water.

The engine is more efficient at hotter temps so many people install FWC kits on their engines. Then only the heat exchanger sees salt water.

I have limited experience with marine engines so I was going to just go with what the manual said. I never heard anything about salt verse fresh water operating temps.

[Guest]

kwmeyer13 wrote:
... My questions are....

...

4) Since I will have the manifolds out what else if anything should I change? Spark plugs come to mind, anything else?

I plan on going with the plank across the gunnels and winch strap idea and using anti-sieze when I reinstall the bolts, Thanks for reading and adding any tips or suggestion.

Hmmm, it seems like you are going to start changing parts. How would you feel if you changed the manifolds and risers and you had the same problem? One manifold running hotter than the other is common on Mercruiser V-8 engines? Often the cause of the problem is not what you think it is originally. The problems you describe could be from a multitude of reasons, ranging from a blown head gasket to a bad temperature sending unit.

I would start here: http://www.boatfix.com/how/cooling.html

First, you could remove the drain plugs on the manifolds and see if crud comes out, or if the passages are blocked. If it drains fast and clear, then it would indicate there is not much sediment floating around. If you want to further ease your mind about the manifolds, you could get your gasket kit and take off the risers and elbows. That will allow you to see if there is "crud" in the cooling passages, and if there is, to clean it out and see if it solves your problem.

Also, I understand that things can happen like this when a cooling hose collapses. Take a close look at your cooling system and identify all the parts to it. Think about what could cause your condition. Your current theory is a intermittent blockage of (a) exhaust cooling passage. If this happened, I imagine your exhaust elbow would become as hot as a skillet and the bellow on that side would get hot or start to burn.

[Guest]

kwmeyer13 wrote:
What is the exhaust/flapper thing? Is it hard to change? How do I know if I have a problem with them?...

It seems very unlikely to me that your water shutter would suddenly shut itself and stick closed at high RPMs

[88fourwinns]

First question, is the boat slipped in salt water South Shore LI or trailered? Because that can make a big difference.I have a lot of experience with moored in salt water boating. Ten years worth up on the North Shore.You should start with your raw water flow, and verify that it is adequate. If the boat is moored or slipped in salt, even if you had the drive painted with Trilux anti fouling, you will get barnacles growing in the water intakes, sometimes covering them, in certain fouling conditions. It has happened to me over the years, and what I do is I jump in the water at low tide and take a thick stiff wire and I rod out the holes. OMC used a screen in the water intake, the barnacles grow behind the screen, I had to remove it to be able to clean them out. BTW, neither Merc nor Volvo used screens on the water takes, but they have more and smaller holes, OMC has 4 big ones. Most outboards have screens.I had a similar problem with my boat after going on vacation for 2 weeks, before that it was perfect, running at 160-170 (Most all OMCs had 160 stats). Then after we came back, the engine was running 10 degrees higher but manifolds (1 season old) were much hotter, there was some kind of a blockage in the thermo housing and I heard it clear itself while checking the raw water flow (low because of barnacles as noted above). After that it was fine again.Your manifolds and risers are past due. In salt 5-7 years tops. Get an IR heat gun, best diagnostic tool, for troubleshooting heat problems. They will start to get hotter as they clog, of if your raw water flow is restricted, but they can rust through and put salt water in a cylinder without warning (except difficult cranking--hydrolock).In salt water I have heard the story about having to use a 140 stat because the salt drops out of solution over 160*, but I have not seen evidence of this on my engine, and I have looked inside the cooling passages I can see. Beyond that, if I could find a 140 stat for the OMC/Volvo housing, I'd use it but to my knowledge no one makes one. Only 160s and most newer Mercs come with 160s too.So start at the entry point (drive water takes) check raw water flow, take off the thermo housing and rod out all the passages, test the thermostat and replace those manifolds.Get an IR heat gun and take readings when its running at the right temps on the gauge. Check under the thermo housing, and the risers and manifolds. Check both at idle and after running on plane. Then you have a baseline, if temps start to rise you know to look for issues.Mine runs between 160-172 on the dash gaugeThe intake manifold right under the thermo housing, is 155-160Manifolds, idle is 95-110, after running on plane, 123-135, after idling in, they drop back to 100.Here's what my OMC one piece manifolds looked like after 5.5 seasons, new vs used. I was able to rod these out, but I had a new set that I put on. You can see one outlet is totally plugged, but that was only half of my running hot issue last year, the other was the damn barnacles in the water intakes.

[img]/media/kunena/attachments/vb/709629=30298-omc manifolds.jpg[/img]

[Guest]

kwmeyer13 wrote:
... I could see the gauge flucuate when the Tstat opened and closed...

Conjecture!

[88fourwinns]

Actually I can see this sometimes, when it warms up it will go a touch over 160 on the gauge, then it will drop back to 160, that when you can tell it opened. Another way to tell (at least on raw water cooled OMCs and Volvos) is to check the temp of the hoses feeding the manifolds. When the stat is closed, they will be cool and about the same temp as the raw water intake hose. But when the stat opens, it allows hot water out of the block and this mixes with the cool water in the thermo housing and the feed hoses for the manifolds will get warmer, not hot but warmer. In fact this is the OMC way of checking quickly to make sure the stat is working. If those hoses start out warm, and the engine does not reach op temp, the stat is not closing, if they stay cool but the engine runs hot, the stat is not opening. Another use for the IR heat gun that helps you figure out things quickly.

[Guest]

The boat sits in the canal behind my house in Freeport. I do regularly clean the drive, trim tabs and such. Last time I did not specifically check the intake ports, so yes that could be an issue. I will make sure they are clean. I am not changing random parts in hopes of correcting the problem. I plan on changing the T-stat because I am not going to try and take it apart the put an old 15 dollar part back in the engine. I know the general life span of manifolds and risers are 5-7 years. These are 12 years old so I felt it was long over due. Do I hope this corrects the problem? Yes but if not then it is on to the next step. I just want to eliminate a few things. Perhaps I should have clarified better that the other things to consider changing would be things like plugs and wires because the manifolds are out not parts to replace in hopes of clearing up my temperature issues. So in a nut shell if I still have the temp issue after the manifolds and risers it will suck but I will deal with it and not wonder if the manifolds and risers are creating this.

[Guest]

kwmeyer13 wrote:
... Perhaps I should have clarified better that the other things to consider changing would be things like plugs and wires because the manifolds are out not parts to replace in hopes of clearing up my temperature issues. ...

Understood. I hope I didn't sound condescending.

[Guest]

kwmeyer13 wrote:
I have limited experience with marine engines so I was going to just go with what the manual said. I never heard anything about salt verse fresh water operating temps.

If you want to run the hotter t-stat then you should look at ceramic coated exhaust.

They are made for salt water applications.