Overheating trouble shooting question

[mr300z87]

I Have been trouble shooting an over heating problem and I have a question regarding water/exhaust flow on a Mercruiser Alpha 1 Gen 2. While running the engine on the hose I notice there are what look like exhaust ports on the bottom of both sides of the gimble housing one side has water coming out and the other does not. My question is should water and exhaust be coming out of both sides and through the prop? If so could this be caused by a clogged exhaust? Which in turn is causing a high speed overheat problem?

Going to pull the riser tube and end caps later today will post my findings. Hopefully with no broken bolts.

 

[Don S]

Re: Overheating trouble shooting question

What engine and year?
There are 2 idle relief ports on the lower part of the transom shield, they are NOT your problem.
Have you changed your raw water pump impeller? If yes, did you replace the gaskets on either side of the base plate of the pump?
Could you discribe your overheat problem for us?

 

[mr300z87]

Re: Overheating trouble shooting question

I have a 3.0L with an Alpha gen2 drive. Idle and low speed all day at 150 degrees. Within a minute of high speed starts get hot to over 200+ will not cool down at low speed until I shut down and restart. As I stated while on the hose I only have water out starboard side of the gimble housing.

 

[Don S]

Re: Overheating trouble shooting question

What year?

Have you changed your raw water pump impeller? If yes, did you replace the gaskets on either side of the base plate of the pump?

Alpha I Gen II could be anywhere from 1991 to 2010

 

[Bondo]

Re: Overheating trouble shooting question

I have a 3.0L with an Alpha gen2 drive. Idle and low speed all day at 150 degrees. Within a minute of high speed starts get hot to over 200+ will not cool down at low speed until I shut down and restart. As I stated while on the hose I only have water out starboard side of the gimble housing.

Ayuh,... Repace the impeller when you rebuild the raw water pump...

 

[mr300z87]

Re: Overheating trouble shooting question

Its a 1993. Going to order the pump kit and re build even though the previous owner told me he just did it at the beginning of this season??? I noticed the Mec part kit is about $150 but there is a Seirra kit that comes with the impeller and plate and gaskets $35, then there is a seirra Kit that comes with all about $100. I have leaned when working on my cars that a lot of aftermarket parts suck and buy mostly OE from the dealer. I that the same with marine parts.

thanks for the replys

 

[Don S]

Re: Overheating trouble shooting question

That 150 dollar kit is probably not necessary. It includes the SS upper housing that seldom fails.
I personally would get the OEM impeller kit, it includes the face seal and installation tool that is not in the aftermarket kits.

The OEM impeller kit # is 47-43026Q06

 

[mr300z87]

Re: Overheating trouble shooting question

Thanks for the part #. I think I read somewhere that the drive fluid need to be drained before I a can separate the lower unit. Is there a seal or gasket required?

 

[Don S]

Re: Overheating trouble shooting question

Yes, drain the gear lube. There is a small quad ring that goes around the oil hole between the upper and lower.
I would strongly suggest (Since this is your first time) to pull the complete drive off the boat, then remove the upper. It's just a lot easier putting it all back together when it's off the drive. Especially on your first try.
There is a gasket set between the drive and bellhousing (about 8 bucks).
Sounds like you are trying to do this with your eyes closed, here is a link to the OEM service manual. You might as well do the job right, instead of how you may think it should be done.
http://www.boatfix.com/merc/Servmanl/14/14cover.pdf

 

[mr300z87]

Re: Overheating trouble shooting question

Thank for the advise. I have a copy of the service manual it is probably where I read it. I have pulled engines from cars and am very comfortable with tools in my hand. Going to give it a shot.

 

[mr300z87]

Re: Overheating trouble shooting question

So here is what I have found. Since the PO installed the exhaust manifold end plates with out gaskets just silicone sealer they were leaking. I have removed them, the inside of the manifold seem OK and water flows through it (used my hose). I then removed the rubber exhaust tubes between the riser and the lower exhaust (they were leaking also) the riser seems rusty but not totally clogged but I can not really tell for sure with out removing the riser. Concerned about breaking the 2 bolts holding it on. Would a partially clogged riser cause a high speed over heat problem? Ordered the raw water pump impeller kit and will install it when it arrives. So at this time I am waiting for the gaskets and pump kit to proceed with further diagnostics.

 

[EddiePetty]

Re: Overheating trouble shooting question

......I notice there are what look like exhaust ports on the bottom of both sides of the gimble housing one side has water coming out and the other does not.

...combining the above statement with your other reported symptoms and replacements, I kinda believe you may have an obstruction within the exhaust passages, specifically broken shutter valve components lodged next to one of the relief ports.

Follow the preceeding suggestions and remove the COMPLETE outdrive to conduct your pump repairs. While the unit is removed/disassembled, troughly inspect the entire exhaust system for obstructions..

 

[mr300z87]

Re: Overheating trouble shooting question

If the broken shutter valve you mentioned is at the top of the lower exhaust tube. There is nothing there looks like it had been removed long ago as I dont see any pieces of it still in the tube. I will be removing the outdrive this weekend if time and weather permits. When I put my hose down the Lower exhaust tube water came out both ports. Waiting for parts, kids and WORK seem to get in the way of having fun.

 

[dingdongs]

Re: Overheating trouble shooting question

plastic tube could be melted when you split lower as well as an impeller.make sure also a good flow is reaching engine as could be blocked with impeller fragments anywhere around water passages.good luck.

 

[mr300z87]

Re: Overheating trouble shooting question

I always wanted to be a boat mechanic I even looked into going to school for it but 20 yrs ago my parents pushed me to get a clean hands job. I am in the computer business. Been working on cars (1968 Plymouth Road Runner and 1988 Nissan 300ZX still own both) as a hobby for years so this is my chance to do what I always wanted.
thanks to all for the advise. I will post my findings when I dig back in this weekend.

 

[mr300z87]

Re: Overheating trouble shooting question

I played boat mechanic today and here is what I found. pulled off the exhaust riser and 2 of the the 3 water passages were completely clogged on both the manifold and riser flanges and the riser looks to be clogged also. To make matters worse while I was cleaning the manifold flange the narrow areas near between the water passage and the exhaust is totally corroded away. Look like and am in need of a riser and manifold. The good news is all 5 manifold and the riser bolts came loose. Going to order ups some parts and try again. I hope the weather hold for the next few weeks.

 

[Simoniz]

Re: Overheating trouble shooting question

I played boat mechanic today and here is what I found. pulled off the exhaust riser and 2 of the the 3 water passages were completely clogged on both the manifold and riser flanges and the riser looks to be clogged also. To make matters worse while I was cleaning the manifold flange the narrow areas near between the water passage and the exhaust is totally corroded away. Look like and am in need of a riser and manifold. The good news is all 5 manifold and the riser bolts came loose. Going to order ups some parts and try again. I hope the weather hold for the next few weeks.

Consider it luck that you found out that the riser / manifold is nearly rusted through with the parts off the boat. Had the water broken through when it was in use, you would have had water running into the engine via the exhaust passages which would have ruined it in pretty short order.

 

[mr300z87]

Re: Overheating trouble shooting question

I was thinking the same thing. The guy I got the the Manifold from said in Salt water (NJ Coast) 5 -7 years is about it for a mainfold. I just got the boat would have been bad to waste a motor on my first outing. Could they have been originals???