Mercruiser issues

T

TPeace

New Member
Jun 15, 2009
23
Raleigh, NC
Boat Info
1977 26' SRV
Engines
Mercruiser 350 Alpha 1 Gen 2
Hi All,

Took our boat out for the first time Sat.
Had some issues and not sure what my next steps should be.
Checked all fluids and plug before going. I'm used to Outboards so this is all new. If someone has a checklist that would be great. I looked on here but didn't find one...
Anyway... we started out slow and I was watching my guages. I noted that the Temp was nearing 200 15-20 minutes into the trip. I also noted ther was a belt squealing but wan't overally concerned with it. We kept easing along and watching the guages and the temp kept creeping up... Now to close to 22 which is all the guage reads. My truck runs about this temp normally 200-210 but felt it odd for the boat. I decided to ease into a channel and check out the engine compartment. Prior to lifting the lid I noticed steam or something out of the vent in the back. I lifted the lid carefully and found lots of water in the compartment. Hit the bilge and pumped itoff and got towed in. I took a look at teh dock and the top hose on the water pump is off. The clamp broke and it got blown off I'm guessing. I didn't notice any type of a slick from Oil, Gas or anti freeze when the bilge pumped off so I think it was all water. What I need to know is what should my next steps be? I don't want to do any additional damage if I can help it and am hoping ther isn't any damage anyway.

Thanks
Tommy
 
Tommy, you are right to be concerned. I would say that the majority of engines which fail prematurely were ruined as a result of being operated at excessively high temperature. High temps really cause a lot of destruction within an engine. If your post reads that the temp hit 220 F, yeah, that is one hot engine. Hope it only ran for a minute or two at that temp.

I would run her at the dock for the next couple of weekends and make sure operating temp is in the norm and nothing else gives way. Keep an eye on the engine and the guage while running. Might want to get an instand read thermal temperature guage and takes some readings as well, in case your gauge is off.

Some may say to replace your impellor but a broken hose downstream of the impeller won't really cause any damage to the impeller so I wouldn't do it if it was recently replaced. If all looks OK, then after a couple of hours (total) running dockside, I would take her out and hope for the best for the rest the season. If it is the original engine, I would put some boat money aside for a replacement anyway.
 
gerryb said:
Some may say to replace your impellor but a broken hose downstream of the impeller won't really cause any damage to the impeller so I wouldn't do it if it was recently replaced. If all looks OK, then after a couple of hours (total) running dockside, I would take her out and hope for the best for the rest the season. If it is the original engine, I would put some boat money aside for a replacement anyway.
Click to expand...

I disagree here. If your water tube came off at the thermostat then that means you were running hot exhaust thru the prop without water to cool it down. It very easily could have melted the implellor within minutes. It still should have been pulling cool lake water, but you never know if the exhaust heated the water it was pulling in the drive.

I would Re-attach your water inlet to your thermostat with new hose clamps and start her up and see what the temperature does at the dock. If it stays cool at idle your implellor is probably ok, if it heats up at idle then an impellor replacement is likely.

If she stays cool, go for a spin. If it heats up with increased RPM's then you may have a exhaust manifold problem.

Good Luck!
 
So what would the temp normally read?
On the instant read thermometer how do you use that ?
The boat has one of the plungers for the bottom draw can
It be started with it and if so do you need the muffs on the
Outdrive?
Would the inlets on the outdrive not keep the impeller cool?
 
Depends on what thermostat you have, but probably around 150 (if your using the 142* thermostat).

I'm not sure what you mean by Plungers for the bottom draw. If your water is drawn thru the outdrive like most, then you will need muffs on it to start it out of the water. You may not get accurate temp readings on muffs though because the water supply is limitited and it might run a little hotter then normal on the muffs.

If your exhaust was at 220*, it very well could have fried your impeller even if it was pulling water from the drive. Hard to say though, your going to have to start her up and find out what she's doing before figuring out the next step.
 
The motor has a hole through the hull where it draws water up into the water pump I'm guessing. It also has the holes on the outdrive like an outboard motor. The boat came with a device that looks like a plunger for a toilet with a hose attachment. I was told it is designed to go over the strainer under the boat where the through hull piece for the water pump. maybe incorrect but that was the info. I was told you need it but not muffs some have told me you need both I'm not sure.

Tommy
 
Ahh ok. So you have a thru hull pick-up for your water inlet, and a plunger type muffs that screws into your garden hose for starting out of the water.

Well, you should only have one water supply. Follow the hose coming off your thermostat. It will either go to a hose on your transom (that would mean your water is being pulled from your outdrive and you would have to use muffs on the drive) or to a hose in the bottom of your bildge (meaning your thru hull pickup is connected and you would use the plunger type muffs on the water pickup on the bottom of the boat).

Good news is that if your using a thru hull pickup then your not using the impeller in your outdrive, so it wouln't matter if it got fried.

Bad news, is if your boat is still over heating after connecting the water supply to your thermostat, then your looking at exhaust manifolds and risers which is a pretty penny.

220* is pretty hot to run that engine. I hope you didn't suffer any damage.

Good Luck!
 
So what is a good temp? and how do you tell what thermostat you have?
 
My truck runs about this temp normally 200-210
Click to expand...

As pointed out, a boat engine operates in an entirely different temperature range. 150-160 is probably considered normal for your engine. If your lucky no damage occured. I would be careful and run it at the dock before I ventured out.
 
Ok.... I'm more confused about this engine temp...
I replaced the clamp on the hose and reset the hose onto the post. The water hose through the hull goes to the bottom post on the pump and the hose that came off was the top hose. This hose goes down one side of the motor across the stern of the motor and back up the other side.
There are no leaks when running it on the plunger. The temp started out slow but then proceeded to reach 170+ I shut it back down but before I did took my instant read thermometer and checked the temp of the water exhausting out of the area above the prop. It only reached 95*
Does this make sense?
 
I would change your thermostat next, and then let it run again. Let it go up to no more than 180. IOW, let it go past 170 and see if she keep rising. It should not go past 180 - no gas powered marine engine should operate at that temperature that I'm aware of. You may have also screwed-up the water temp sensor when you let her get up to 220+ so keep that in mind. An instant read therm of the water is pretty much useless. You need to get an instant read thermal therm and get a sense of the temperature of the metal components for which the cooling system is design to protect against excessive heat. Point the red dot at the manifold, thermostat housing and the valve cover, and tell us what the temperature readings are....
 
Yup replace the thermostat with a 142* that should keep your engine around 150-160. Water out the back doesn't mean anything, your worried about your engine temp.
 
Ok so how can I determine exactly what enging type I have so I get the correct Thermostat? Is there a plate on the motor somewhere? I looked but didn't see one.
I'd like to find out year and HP and such. Was told it was a Mercruiser 350 it has a Alpha 1 with VenSura SS Prop 14 Dia, 19 Pitch. Not sure any of that helps just sharing what I know.

Tommy
 
There should be a plate on one of your valve covers with engine info, but it wont tell you what thermostat. I can almost guarantee you need a 142*. Most 350's run with a 142*, and all of the older ones do.
 
Will look again in a few.... Thanks for all the info you guy's are very helpful to me as a newbie ;)

Tommy
 
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