See full version: How to Replace a MerCruiser Alpha Thermostat
Make note where the indexing notch or the wobble valve is positioned. Grasp the thermostat inside the housing with pliers. Pull the thermostat out of the housing and discard. Clean the mating surfaces to remove all traces of gasket material. [links]
The thermostat in your MerCruiser Alpha monitors the temperature of the engine. The impeller inside the out-drive sucks water into the engine. If the engine temperature is too hot, the thermostat opens to allow more water into the engine. If the engine is too cold, the thermostat closes so that the water cannot enter the engine to cool it. Replacing the thermostat in your Mercruiser Alpha is definitely a DIY project, and you can find a new one at your local boat shop.
Open the engine cover of your MerCruiser to access the engine. Locate the thermostat housing. It mounts to the top of the engine near the front. There are four hoses that connect to the housing and are attached with hose clamps.
Remove the two bolts securing the housing to the engine block. Pull the cover off the thermostat housing. Remove the gasket.
Position the new thermostat according the indexing notch or wobble valve. Place the new thermostat in the housing. Apply the new gasket between the cover and the thermostat housing. [links]
Another common typical example that we see all the time is the customer who has just started using his boat after it has been sitting for a year or more. "It was running fine for the first 1/2 of the day" they usually say. We usually find that the rubber water pump impellar blades have turned brittle from sitting. After the impellar was used for a couple of hours it crumbled to bits and the engine overheated. If your boat has been sitting for a year without being run, you should rebuild the water pump. here
For example, if you have just run aground on a sand bar and now you are overheating, chances are good you have sucked up some sand and possibly ruined your water pump impellar. Not only will you have to rebuild your water pump but you might have to backflush the cooling system to remove the sand. here
The water pump might be fine but it's a good place to start. The pump should be replaced each season. If you are overheating and you haven't replaced the pump for a while, do it. Replacing the pump will "kill two birds with one stone". Not only could it correct the entire problem but it will also get some scheduled maintenance out of the way. Even if it doesnt correct the problem at least you can rule it out as being suspect. [links]
Excessive overheating can ruin your engine.
If your engine is overheating turn it off and do not run it until you have fixed the problem.
Overheating is a problem which can be diagnosed through a process of elimination. The best way to tackle such a problem is to first consider the obvious. more
Align the thermostat housing on top of the mounting surface and reinstall the bolts. Snug them securely but do not over tighten. Tighten them to 30 foot-pounds using a torque wrench. Reattach the cooling hoses to the housing.
Open the engine compartment and locate the thermostat housing. It will be mounted on the front center portion of the engine block with four hoses connected to it.
Remove the old gasket material from the mounting surfaces with a razor blade scraper. Place the new thermostat into the housing in the proper direction. Apply gasket sealer to the mating surfaces and place the thermostat gasket over the opening on the engine.
Remove the two bolts holding the thermostat housing to the block with a socket wrench. Carefully pry the housing loose from the block with a small flat screwdriver. Be careful not to damage the housing or mounting surfaces. [links]
Examine how the old thermostat is mounted into the housing. The new thermostat will need to be placed in the same order to operate properly. Some models are equipped with a plastic spacer holding the thermostat in place that will need to be removed first. Remove the old thermostat with a set of pliers. [links]
Remove the hose clamps connecting the cooling hoses to the housing with a large flat screwdriver. Remove the hoses and inspect them for cracking and softness. Replace them if necessary. here
Post by CobaltRick » Wed Jul 10, 2019 10:34 am
Post by akorcovelos » Tue Jul 09, 2019 12:57 pm
ok.. I'm back.. Yesterday I bought a replacement thermostat from a local marine store just because it was convenient and I was already getting a few other things. Its a MerCruiser part that was claimed to work with my engine. Well, the long and short of it is that the t-stat didn't seat the way the old one did and I closed it up the best I could and eventually ran the engine but it was leaking through the bolts holding things together. So, I ended up watching a few YouTube videos on t-stat replacements on these boats and it appears there's a sleeve that's either plastic or brass (Depending on age perhaps) that is supposed to hold the t-stat in place down the "throat" of the opening.. It does in fact appear that I have a brass sleeve down in mine but I've got no ideas on how to remove it. Does this ring a bell with anyone here? I found a thread with some pics associated with this.. I guess I need to find a way to remove & replace my own sleeve .. I've got no idea whether I need a cut-out on mine or not.. If there are multiple designs for my year I'll have to look into that. Unfortunately I need to spend more time on this and just haven't had a large block of time to devote to it in the past couple of days. Hopefully I can get the sleeve out and put a new one in whether its plastic or brass and whether it has a cut-out or not.
[links]
[links]