Alpha 1 gen 2 5.7L overheating

[mrjamieson]

Hi folks, Sooo, I have a 1992 Wellcraft 233 project boat. Brand new Marine Power 5.7 Vortec, EST, carb, electric fuel pump engine along new new Mercruiser 1.47 outdrive, new transom assy, transom plate, P/S cooler, coupler, etc... It's raw water cooled. Just started it up, with the good flow to the muffs and it proceeded to overheat. The dash gauge got up to 180 within 5 minutes. (My infrared thermometer stopped woking) The old engine had the obsolete "flat" t-stat housing. This has the new style housing with the "T-ball" and 140 degree t-stat. I took the input hose off the t-stat housing and ran the engine @1000 rpm's for 15 seconds and didn't even get a gallon of water BUT prior to that I was getting water out the back from the brand new y-pipe and flappers. Now, because of health reasons all the new parts sat in the garage for about 14 months. Could the impeller be bad because it sat for so long?? Any help would be appreciated.

 

[Rick Stephens]

First thing is to pull and hang the IN line at the thermo housing - the one coming from the oil cooler and transom. Hook up muffs, water full on, fire up. Do you get at least 5 gallons a minute flow from that hose? If not, then something is plugged or impeller is bad.

 

[mrjamieson]

First thing is to pull and hang the IN line at the thermo housing - the one coming from the oil cooler and transom. Hook up muffs, water full on, fire up. Do you get at least 5 gallons a minute flow from that hose? If not, then something is plugged or i

 

[mrjamieson]

First thing is to pull and hang the IN line at the thermo housing - the one coming from the oil cooler and transom. Hook up muffs, water full on, fire up. Do you get at least 5 gallons a minute flow from that hose? If not, then something is plugged or impeller is bad.

Should I be at idle? I was at 1000 rpm's for 15 seconds and didn't even get one gallon. I think I might pull the drive and hook the hose right up to the transom assembly.

 

[achris]

Should I be at idle? I was at 1000 rpm's for 15 seconds and didn't even get one gallon. I think I might pull the drive and hook the hose right up to the transom assembly.

That test must be done in the water, not on the hose at home.

 

[mrjamieson]

Not sure what you mean. I want to eliminate the impeller as the cause. How do you recommend suppling water to the t-stat housing?

 

[achris]

. I want to eliminate the impeller as the cause.

Then remove the drive and put a hose into the water passage in the bell housing.

... all the new parts sat in the garage for about 14 months. Could the impeller be bad because it sat for so long??

If the impeller just sat in a bag, no. If it was installed and sat with a set on it, then I'd bin it and start again.

Chris........

 

[dubs283]

Not sure what you mean. I want to eliminate the impeller as the cause. How do you recommend suppling water to the t-stat housing?

Seems like he's recommendingthe test Rick mentioned should be performed with the boat in the water, not running on muffs.

Based on your first post, even running on muffs you should have better flow than you describe. As others have mentioned, the issue is either a faulty impeller/sea water pump issue or a blockage between the pump and t stat housing.

IME aftermarket sea water pump/impeller repair kits have quality issues and are not recommended

 

[mrjamieson]

Then remove the drive and put a hose into the water passage in the bell housing.

If the impeller just sat in a bag, no. If it was installed and sat with a set on it, then I'd bin it and start again.

Chris........

Thanks Chris. I wasn't sure what test you were referring to which had to be done in the water. I'll pull the drive, test the flow and replace the impeller.

 

[Lou C]

The reason why the raw water flow test should be done in the water is that the hose water pressure can mask a weak impeller.

 

[Rick Stephens]

That test must be done in the water, not on the hose at home.

No. Purpose here is to find out if any water is getting through the impeller. That test is fine at idle on muffs. Best place to start to find out if the impeller works at all. Silly to haul it to a boat ramp just to find you don't get any water through the impeller.

 

[mrjamieson]

Seems like he's recommendingthe test Rick mentioned should be performed with the boat in the water, not running on muffs.

Based on your first post, even running on muffs you should have better flow than you describe. As others have mentioned, the issue is either a faulty impeller/sea water pump issue or a blockage between the pump and t stat housing.

IME aftermarket sea water pump/impeller repair kits have quality issues and are not recommended

I ordered the impeller kit BPI12080 From Basic Power Industries. Should I get the OEM mercury parts only??

 

[mrjamieson]

I ordered the impeller kit BPI12080 From Basic Power Industries. Should I get the OEM mercury parts only??

Also, should I replace the impeller housing too?

 

[Rick Stephens]

Most rubber parts bought OEM from Mercruiser will last longer than aftermarket. Especially true of bellows, but also of impellers. Merc gets the rubber right every time.

 

[mrjamieson]

Most rubber parts bought OEM from Mercruiser will last longer than aftermarket. Especially true of bellows, but also of impellers. Merc gets the rubber right every time.

Update. Took the outdrive off and used the hose. Ran the motor for about 10-15 minutes. All is well. Normal readings all around. Rpm's between 600-1500. The gauge ran a little higher than the infrared thermometer but then I noticed I used teflon tape on the temp. sender. Let's see what happens after a change the impeller.

 

[achris]

... then I noticed I used teflon tape on the temp. sender. ...

Yeah, that's not good. Need to remove it and pull all that tape off. If you feel the need for a 'sealer' try Loctite 515...

Chris..

 

[Lou C]

I recall thinking of this when I I stalled the temp sending unit in the intake (had to clean up all the rust & paint) so what I did was thread it in to see about how deep it threads in. Then I just used a bit of Evinrude gasket sealer on the threads at the very end of where it threads in to prevent leaks but not the full length of threads so as not to interfere with the ground path.

 

[mrjamieson]

Update. I installed an OEM impeller. SAME PROBLEM. I then matched the new Sierra temp. gauge with a Sierra sender. NO teflon tape this time. Better results but still ran hotter than I like. Built a container to submerge the outdrive and ran it. Everything looks good. The gauge never went over 170 from idle to 1000 rpm. Eventhough the old engine ran fine on muffs, this one will not. Lesson learned. Forget muffs! Thanks Achris and everyone who took time to respond.

 

[nola mike]

Update. I installed an OEM impeller. SAME PROBLEM. I then matched the new Sierra temp. gauge with a Sierra sender. NO teflon tape this time. Better results but still ran hotter than I like. Built a container to submerge the outdrive and ran it. Everything looks good. The gauge never went over 170 from idle to 1000 rpm. Eventhough the old engine ran fine on muffs, this one will not. Lesson learned. Forget muffs! Thanks Achris and everyone who took time to respond.

Your lesson is backward. You should run on muffs, not in a container. 170' at idle with a 140' stat is way too hot.

 

[Rick Stephens]

Running a Merc outdrive in a bucket of water usually doesn't work out well. The pump needs to be fully submerged, and that is tough to do. Those pumps can not pull water, they have an open vent air bleed port to prime them - meaning they prime by submersion. Mostly they get burned up when attempting to run in a bucket.

If you do not have enough water pressure/flow to run on muffs at wherever you are working on the boat you need to fix that. Go somewhere else or improve your hose flow - that's the lesson.