Can run with no thermostat as a test on a temp issue?

[USA_boater]

Boat sat for 5 yrs before I bought it (has 4.3 GL-C). If it idles on trailer it will not overheat but will go up 3/4 temp gauge...taking RPMs up a bit will drop temp to just above half but not ever run below half once warmed up. I changed the impeller today and found it did have one torn vain missing about half of it; the rest were brittle but intact. After changing impeller, the temp gauge behaves the SAME with the new impeller (on trailer).

So next i took off the t-stat housing and found tons of rust/flakes in the intake and in the hoses and the t-stat was full of buildup and rust. I ordered the wrong t-stat kit so I have to re-order and while I'm waiting, I'm going to scrape loose the scale in the intake through the t-stat hole and then shop vac it out. I am also going to loosen the rust in the hoses and shop vac those too and then maybe replace the circulation pump hose that is sorta brittle and has lots of rusty buildup in it. I'll then clean the t-state housing inside with scotch brite, wire brush and WD40 and then get it as clean as I can where I can reach inside it.

BUT I do have a spare gasket and wondered if I could run it to flush the trash with no t-stat installed and also see if it heats up the same or if it is any better running with no t-stat. Can I do this and what else should I be doing to try and make sure this boat is lake-ready as far as the temp issue???

I already changed the oil and filter and fuel filter and poured seafoam in the gas...the boat HAS RUN on water twice since I got it; it was the second time out for testing that I noticed the temp creeping up so it prompted my actions I had already planned to do to come sooner rather than later.

 

[tpenfield]

No numbers on the temperature gauge?

We we will allow you to run the engine without a t-stat for testing purposes.

Keep in mind that you may have rust flakes clogging the water passage ways in the exhaust manifolds and risers as well, which restricts the water flow through the engine.

 

[Lou C]

Exactly as Ted said, you likely will see the same thing if you inspect the outlet ports of the exhaust elbows. You might consider removing the front circulating pump (pick up a new one, the bearings are probably going to go bad next lol) and with the block drains open, flush the block out with a garden hose using the water pump intake port on one side of the block. Rod out the block drains with a pick first. You will be surprised what comes out! Then remove the exhaust elbows after draining them and inspect the manifold to elbow gasket sealing surface. If eroded they can be decked by a machine shop but if there is a lot of flaking corrosion it might be time to replace them. All of this is why I say closed cooling should be standard (at least a half system) on cast iron inboards. For now though if the engine turns out to be good, just flushing out the block and replacing the exhaust, thermostat and maybe the housing should help. As far as the impeller, did you also replace the wear plate? If these get scored, even a new impeller won't pump correctly.

 

[Scott Danforth]

find the missing impeller piece that is part of your problem. it went somewhere and is now blocking flow

no - you cant run without a t-state, running without a thermostat will run hotter in many casesas the water flow will be too fast and not be able to pick up heat. it also affects the flow/distribution to the motor and exhaust.

if your carbureted and raw water cooled, its a 140 degree thermostat.

 

[USA_boater]

okay thanks fellas here is my response and questions:

I did do the cleanup as I mentioned in original post...I just bought the boat and am trying to get to use it some THIS season. I figured I'd have to replace the risers at some point due to age and sitting (is that what u meant by elbows???). I was hoping to do "some" repair and get it good enough for a few outings and then attack it further when summer is over.

- When I replace the stat is there any procedure that must be done to purge air from the system? I saw the t-state housing had a purge port like some cars do.

- Do you think I could get away with doing the stat, impeller, circ pump, flush as Lou said, and then also pick the drain ports out?

- If no to above question, will I need gaskets and such for the risers? How hard are they to remove/install?

- Are you sure the VP 4.3GL has a wear plate? I saw vids of Merc Alphas that had it but no mention of one on VP in the tutorials I viewed before I swapped out the impeller

- I am hoping as I work on this there is no chance doing one thing at a time leads to the fix just being nullified by being clogged again by loose rust flakes (such as the new stat when i install it). Can I do everything but the risers and give it a try without the risers rust clogging up the new stuff if I don't take them off until after season ends?

- Stat that came out said 160*, the p/n sierra lists is a 150*...can you point me to a correct 140* kit? My gauge is 0-220 and I guess it runs 190-200 if gauge is accurate.

I REALLY hope the block & heads are okay!!! I'd love to upgrade the intake manifold too if its bad but I hope the risers, pump, impeller and t-stat and a good flush is all it will take. I won't have the time and funds to mess with anything beyond that for awhile...I will try what you guys said and report back.

THANKS SO MUCH - LOU, I SENT YOU A PM WHEN I JOINED...you saw me on the old JU forum back in the day.

EDIT: I know about the block and manifold drains...how do you drain/ream risers if not removing them? Can you just remove the metal plugs (hex head I think)? Or will draining and picking out the other 4 drain ports be sufficient? And I stress, once the system is opened up, is there any concerns of starving the engine of cooling from ait pockets like on a closed automotive system? This is a raw cooled, carb 4.3GL-C

 

[Scott Danforth]

get two manifold to elbow gaskets. pull the elbows off the manifold and inspect

there is also a drain on the intake manifold where the thermostat is. dont forget that when it comes time for winterization.

if your motor is running 190-200, something is wrong. at most it should be running 10 degrees higher than the t-stat rating

get an IR thermometer to verify.

 

[USA_boater]

Thanks, I have an IR but haven't tried that yet; but when the boat is idling on trailer, the risers and exhaust manifolds are not hot to the touch at all...maybe warm to luke warm...The t-stat housing is off while I'm waiting on parts so I won't be able to try the IR thing until I get it all back together..I went ahead and ordered a new circulation pump too. If I am just getting elbow gaskets, is that so I can inspect the water ports and sealing surface of the risers and exhaust manifolds? Or is that so I can look into the ports and try to remove scale and any obstructions? I want to be clear on what I'm doing if I do take the elbows off...I would rather just wait until end of season and replace them as a maintenance item since they are 14yrs old and the boat was run mostly in a lake with higher salt content as compared to regular freshwater lakes (Texoma).

 

[USA_boater]

Well I replaced t-stat and water pump and rodded out the block & manifold drains and flushed the block and manifolds as you guys instructed (with water pump off)...lots of trash came out and I did this until clean water with no more flaky trash.

I then ran it on the trailer and saw some improvement. After idling for 20-30min, it would go just above half but not as high as before, then if I take RPM's up in neutral, it would drop back to half...not sure what half is on the gauge (are gauges split 50/50?). gauge has 120 on bottom and 220 on top so half should be 170*? So it would seem on trailer idling a long time i never go over maybe 175-180ish Then a few revs and it goes down closer to half way point. It isn't overheating though but until I take it to the lake I won't know for sure...But my work definitely paid off and thanks for the advice...

I am not going to open the exhaust until after season but I did buy some new OEM riser to manifold gaskets. Do people just typically replace the risers or are the manifolds replaced along with them typically?

 

[Bondo]

I am not going to open the exhaust until after season but I did buy some new OEM riser to manifold gaskets. Do people just typically replace the risers or are the manifolds replaced along with them typically?

Ayuh,..... With both, it comes down to how much cast iron is left at the gasket matin' surfaces,.....

Yer lookin' for good clean flat surfaces, atleast a 1/4" wide to support the gasket,.....

 

[USA_boater]

Okay then, I guess I'll find out when the time comes...I used Indian Head gasket shelac on the wp gaskets and no leaks but on t-stat housing, I only used it on one side of the gasket and the non shelac side is sweating a little (seemed to stop after warm up). That got me thinking, on the exhaust gaskets, are you supposed to use any chemical sealant (copper spray maybe?) on the gaskets to seal them? I don't want any leaks if I do all that work to replace manifolds and risers.

I so much with they made headers for the 4.3 GL but I guess it would get too hot in the engine compartment?