Stringer 800 now runs hot ONLY at WOT

[studdy05]

Just replaced and fully rebuilt an 800 stringer that sits on a 83 5.7 L V8 because it was running hot. Found a fully destroyed impeller, and kept finding little impeller pieces everywhere in the upper during rebuild.

Had it out a few times since the rebuild, and at idle the temp is fine. Under power at 2000 to 2500 RPMs the temp is midline on the dial and smooth running. At 3000 I see a little more creep in the dial toward the out of bounds area.

At 4000 RPMs - my WOT - under power, it actually wants to enter no mans land and run hot. Of course I won't allow that, and I back down to 2200 RPM's and within 20 to 30 seconds I cool right back to midline on the temp guage.

It's no fun to run if I can't gun. Please pitch any sugguestions ... thanks.

 

[studdy05]

Re: Stringer 800 now runs hot ONLY at WOT

BUMP...someone has this answer...lets hear it!

 

[chiefalen]

Re: Stringer 800 now runs hot ONLY at WOT

you sure you got all the pieces out of the outdrive passages also?you got all the pieces in the intemediate housing?you also got all the pieces out of the hose that runs to the thermastat?in the thermastat housing no pieces in there?if all clean than the engine mounted water pump how are the vanes on that?you have a strong telltale stream of water on the ball gears on the outdrive.good stream of water comming thru the propeller?

 

[captk]

Re: Stringer 800 now runs hot ONLY at WOT

you might try running with clear hoses to see if you are getting air bubbles in the cooling water. Did you change the housing and plate and seal it with perfect seal?

 

[WizeOne]

Re: Stringer 800 now runs hot ONLY at WOT

is your guage calibrated? what thermostat are you running? have you tested it in heated water that is the same temp as the rating.

push comes to shove, I like to check the temp with an infrared temp gun. I was showing an overheat and the gun showed the engine was fine. I had a wrong sending unit installed.

also you could temporarily run a clear hose up from the outdrive and check for bubbles and even disconnect it at the thermo, momentarily to check the flow at higher rpms.

 

[79Glastron]

Re: Stringer 800 now runs hot ONLY at WOT

If the water supply is ok and the stat is ok, I would check to see if you have a rust plugged exhaust manifold and riser/elbow. They will clog up and cause a lot of problems too. One more item, is the engine water pump working correctly? The impeller could be worn and/or rusted away. Good luck!

 

[studdy05]

Re: Stringer 800 now runs hot ONLY at WOT

you might try running with clear hoses to see if you are getting air bubbles in the cooling water. Did you change the housing and plate and seal it with perfect seal?

This is where my inexperience shows. I TRIED to get a near perfect seal on the new housing plate, and all the way back out of the upper unit and even the connections to the lower unit. Never ran vacuum tests and other than that I dont know how you can tell.

Also what would bubble suggest if you found them? (imperfect seal???)

On such an old boat, I am seriously considering testing the therm reading but wanted to rule out my rookie errors first before testing the hopefully good equipment.

Risers are clean and not blocked btw

 

[studdy05]

Re: Stringer 800 now runs hot ONLY at WOT

Replaced power steering pump yesterday...and this is highly related.

It ate power steering fluid like mad. None was in the bilge...until it got hard to steer. I was treating these as two seperate issues.

My guess is that the power steering cooler - which is the first stop out of the intermediate housing before the thermostat - is clogged because the internal coil is busted from being frozen. (A new winterization issue manual does not mention that and Don has said buy the real things not Seloc etc.)

Did notice slight film on water yesterday while stopped but had just greased lower unit tilt arms so I didn't know exactly what the film was from. I now highly suspect the coil is broken.

Going to replace the radiator, refill the new power steering pump with fluid, and head back to the lake to confirm this issue is resolved and will repost.

Just makes too much sense.

 

[WizeOne]

Re: Stringer 800 now runs hot ONLY at WOT

You cannot have an 800 stringer if you have 'lower unit tilt arms' and power steering.

 

[Manipulator]

Re: Stringer 800 now runs hot ONLY at WOT

If you have a 83 then its a stringer. I have the same set-up too. I was thinking the same thing as far as the cooler being clogged. Getting through to the bottom of the thread I see you caught it too. I would imagine you have some debris in there from that blown out impeller. That is where I would look, looks like you need to address the power steering leak anyway. Another thing to consider is the swivel bearing. Exhaust can enter into the cooling in the upper unit and cause air bubbles. Typically a simple fix is to grease the heck out of it. Look towards the front of the lower unit, you will see a hole there, that is there so you can grease the bearing. You will need a small grease gun with a small nozzle.

 

[studdy05]

Re: Stringer 800 now runs hot ONLY at WOT

Gonna bump this again. Few things have changed since last post.

First, I burned up my gears in my upper (unrelated issue - didnt add enough lube after resealing it..stupid costly mistake...hint for newbies - under pressure of new seals give that oil plenty of time to drain down or measure!)

Second, Manipulator was right, I did have a crack in my exhaust seal. I changed that, lubed the dickens out of it, and that helped.

However, I still borderline over heat at WOT. I took the exhaust manifold and risers off last season and I think they are either the originals or dang near close to it (83 model).

I added a 12v inline sea water assist pump to really push the water through the engine thinking I just didn't know how to correctly install an impeller though I have done it now 10 times at least. The inline assist pump kicks in manually at the helm when I over heat - heck I can put out fires with all the pressure I have. I know this is not the problem, now. I got sea water. Boy do I have sea water. Even with all that, I can still get close to redline at WOT after 2 minutes. (2200 RPMS is OK, but I cant plane out at that.)

When the lake water warms up this summer its gonna be worse, I am sure.

New thermostat.

New hoses.

I am down to risers, exhaust manifold or timing too far advance issues. At least I think that is where this leads.

Is there a way to tell which way to look? One riser seems alot hotter than the other but smarter folks than I say this is often normal.

 

[studdy05]

Re: Stringer 800 now runs hot ONLY at WOT

For giggles I just went and bought a new temp guage and sending unit, this one with actual water temp rather than just cold normal and hot like the original 83 was.

Installed it.

In the slip it idles at 160 degrees, throw the gas to it to 4000 RPMs and it bumps up to about 180 then trickles back to 168 or 170 and sits.

Now that is not under load, which I know is different, but the guage behavior is now telling me something wildly different than before.

Can someone with a 5.7L stringer 800 tell me what temp you get at WOT? And what is the danger zone HOT temp before you turn it off?

 

[studdy05]

Re: Stringer 800 now runs hot ONLY at WOT

Here are my results under a load:

160 degrees at idle
170 at 1000 RPMS
180 at 2000 RPMS
190 at 3000 RPMS

From 170 degree to WOT at 4200 RPM's I get about 4 minutes before it hits 200 to 205 where I shut it down.

Actually I dont shut it down, I throw it in neutral and move it to 2200 RPMS and it cools down to 175 in 30 seconds or so.

Ideas?

 

[GunHoInc]

Re: Stringer 800 now runs hot ONLY at WOT

So did you check your flappers as well? And how did your risers and exhaust look? Just curious to compare to my issues. LOL

BTW you can get an IR thermometer gauge at Harbor frieght for $50.00 a good testing tool to have.

dAvE

 

[GunHoInc]

Re: Stringer 800 now runs hot ONLY at WOT

In my Shop manual it says to check the timming and too much oil in the crank case will also give you a WOT over heat issue.

dAvE

 

[GunHoInc]

Re: Stringer 800 now runs hot ONLY at WOT

So how did the new manifolds and risers work out?

Paulie

 

[THE BEEF]

Re: Stringer 800 now runs hot ONLY at WOT

I have a 5.0 800 stringer mine runs steady 160 degrees all the time.
I did have an issue with over heating at one time .It was the swivel bearing seals going out.I greased the poop out of them 12 shots of OMC triple guard grease. took care of the problem the rest of the season. The seals are there to keep the grease in . When you grease them like that it seals the water pump pickup on the upper gear box from exhaust gases getting sucked in around it.
Beef

 

[studdy05]

Re: Stringer 800 now runs hot ONLY at WOT

I replaced the swivel bearing seals, and regreased. As the water has warmend up in the Gulf, so has the temp issue.

And now I have also replaced these items:

both manifolds
both risers
both head gaskets...and I thought head gaskets were gonna be the winner
engine water pump

Took it for a quick spin and for all that ... I got the exact same overheating results...didnt change not one thing except my wallet...

In June I removed the thermostat and saw some improvement in that I only will overheat now if I push it over 2800 RPMS...and at about 2200 RPMS it runs just great.

I am all the way back to where I began, which is pulling the upper and a new sea water pump. This time, I bought an entirely different upper, yes I now have two, and am going to swap it out.

As I pulled the boat out, I got a nice little suprise on my intermediate housing.

It's the other pic...so I am replacing the Intermediate next week as I replace the Uppers.

And yes I am going to regrease the fire out of that swivel bearing...but truth be told, nothing in the entire cooling system is left that has not been replaced new or replaced with heavily vetted used OMC OEM equipment. I have spares of everything.

 

[studdy05]

Re: Stringer 800 now runs hot ONLY at WOT

I noticed something different in the old and new intermediate housings.

On the very bottom of my old one, there is no plate on the bottom of my exhaust hole. Never has been.

My new IH has a plate over the very bottom of that hole. Hard to see in the old pic but obvious in the new one.

Could it be that the lack of the plate causes water to flush up into the exhaust under high speeds and restricts the flow of water out of the elbows causing enough restriction to heat my engine?

I mean there is a hole there that is exposed without that plate on it that would be at the right angle to allow water to come right back up in my tailpipe if you will.

Just throwing this out there...the plate on the new IH has thrown me.

 

[BLDFW]

Re: Stringer 800 now runs hot ONLY at WOT

I replaced the swivel bearing seals, and regreased.
........

And yes I am going to regrease the fire out of that swivel bearing...but truth be told, nothing in the entire cooling system is left that has not been replaced new or replaced with heavily vetted used OMC OEM equipment. I have spares of everything.

I've been following this and wanted to ask you about your regreasing steps....

I just replaced nearly all the seals in my outdrive including the swivel housing seals. Was I supposed to have greased the 1" wide gasket like liner inside the swivel housing? Or is that more for worn out seals?

Thanks.