Alpha Sterndrive water/exhust question

[NConroy]

I recently replaced the lower drive water pump on a eight year old Alpha One Gen II sterndrive. When remounted and on test with the rabbit ears, engine temp is OK at idle, will not test at higher revs until I get it in water.

My question is, how do I tell if I have transom or thru prop exhust. On test, all of the exhust and a lot of the water was comming out from the transom area. But some water was comming out the prop area (prop removed). Can anyone give me an overview of the two types of exhusts systems on the sterdrive. Also the water outlet.

The more work I do, the more I see needs to be done. I thought replacing the water pump would be a good preventitave maintance project. The reaility is that I now need to replace the thermostat (very small project), and am wondering if I should be replacing the exhust tube and bellows, gimbil bearings etc. Where does all stop? Considering the cost (time and cash) it may be better to just get a referbished stern drive.

Anyway, the last few line were just a little rant, but I would appricate any help with the exhust and water outlet question.

 

[HT32BSX115]

Re: Alpha Sterndrive water/exhust question

Howdy,

You have "thru prop exhaust" unless you have large holes in your transom for exhaust. (you could have both if you had exhaust diverter valves AKA "Capts Call" )

Almost all Mercruisers have a path for water and exhaust to come out of the bottom of the transom. It's so it drains all the water when the boat is out of the water. You'll see a little exhaust there too....

Why do you think you need to replace the thermostat? They don't fail very often.

If you're replacing the raw pump, and the old one was shredded, you may have pump remnants downstream of the pump crammed into either the PS or oil coolers and/or thermostat housing.


If it's 8 years old you may not have to replace the drive and exhaust bellows. (but if the drive bellows is leaking it may be defective.) The exhaust bellows is not a big deal....you can even run without it...[I wouldn't]

If you have already pulled the drive, and everything in there is rusty, you may have to replace the U-joints, yoke and gimbal bearing. You don't know until you get it apart.

The gimbal bearing lasts a LOT longer than 8 years though.

It all depends on how well the previous owner took care of it all. Was it left in salt water and not serviced every year? poor maintenance can ruin a drive very quickly. My 66 Marktwain (150 Mercruiser) was well maintained and lasted 39 years before I sold it!

Go to http://forums.iboats.com/showthread.php?t=288430 and look around. There's a lot of info there.


Cheers,


Rick

 

[NConroy]

Re: Alpha Sterndrive water/exhust question

Thanks Rick
Boat came from Florida to UK in 2004. Than came to Ireland in 2006. I can say that since 2006 it has only been in lake water, taken out each winter.
I bought it in 2007. I do know that previous owner had no interest in the maintaince element of boat ownership and judging by condition of engine compartment, not much attention was paid to that area.

I am glad to hear that the bellows, gimbals etc should last longer than eight years.

I only replaced the stern drive water pump because I reckoned it had not been replaced since new and was worried the impeller may have been damaged by normal "wear and tear" over the last eight years. Various sources recommended yearly change for impeller, others said three to four. One site rated the Gen I for 50 hour and the Gen II for 200. In fact the impeller was perfect and I am pretty sure this was first change. There was leaking from the gasket at base of stainless steel housing, but no apparent damage.

I had noticed the temp never went above 110 degrees when running. When I checked the thermostat while I was doing the pump replacement, found it was partially open when cold. New one on the way.

I had always thought that it was a thru prop exhaust, but on test did not see much exhaust coming out of prop, so just wondered? Are there any checks I should do to establish why exhaust is mostly coming from transom area.

Best

 

[HT32BSX115]

Re: Alpha Sterndrive water/exhust question

Which engine is it? (Year model, serial etc)

It's possible that you have a "flapper", (exhaust shutter), (or a piece) that has broken off and is lodged in the exhaust bellows or in the exhaust path in the drive.

It's normal however for see exhaust and water exiting in the lower part of the gimbal on the outside when you're running on a hose adapter.

Also, since you don't know if it's been done (I'm assuming it's a "raw" salt water boat) you should probably remove the risers and carefully inspect the risers and manifolds for corrosion and then of course, replace the riser gaskets. When you get the risers off you can have a look at the water shutter(s) in the exhaust Y-pipe or downtube etc.

Those sometimes break off and end up down in the area leading to the exhaust bellows to the drive...

 

[Rocky_Road]

Re: Alpha Sterndrive water/exhust question

Don't get too alarmed...on the 'muffs', 90% of the water/exhaust will exit around the transom, and only a small amount from the prop.

All that changes...on the water!

Go boating!

 

[Schmoe]

Re: Alpha Sterndrive water/exhust question

I second that!!!