mercury 800 hot tall tale stream

[CamelStyle]

I've got a ~1970s era mercury 800 80hp that I've been rebuilding that was given to me.
I rebuilt and replaced a bunch of things already including the water pump.
I took it out for a test run and noticed the motor running pretty hot to the touch and the tall tale was extremely hot.

I noticed on the exhaust manifold(baffle?) there was a brass cap and on the bottom of the exhaust cover there was a fitting with a hose that was capped. Should these be connected together? My tall tale is connected where the spark plugs are to a fitting there.

I opened them up (water jacket?) and didn't notice too much junk but cleaned them up afterwards but haven't closed it up yet.

As for the test run, I feel like my throttle cable needs adjustment I couldn't get past 2000 rpm and was bogging a-bit so I pulled the carbs to clean. I downloaded the service manual but cant seem to figure out what those 2 areas are for any help would be great

anyways on the picture in yellow was a hose that was capped and the red on top had a brass plug (is that used to flush? or should those be connected the yellow bottom one when i ran it in a barrel and took the cap out of the hose it had water coming out

 

[Scott Danforth]

when you replaced the waterpump, did you replace the tube seal at the bottom of the power head?

 

[CamelStyle]

when you replaced the waterpump, did you replace the tube seal at the bottom of the power head?

i had that taken apart and had some issues getting the copper pipe to fit.. possibly could of damaged something there... while putting it back together but i know for sure its seated correctly. not sure on condition of the seal

 

[jimmbo]

70s Era Merc 800 means 1970, 71, 72, or 1978
Before pulling the carbs off did you verify that they were opening fully? BTW, you don't adjust the Cable Length to get the carbs open fully. You adjust the length once the Idle Speed is set.
Now that the Carbs are off, you will need to verify and adjust the Sync between them and the Spark when you reinstall them.
The Teletale connection point has moved around on some engines over the years. I have seen them located on the Water Jacket Cover, near the Spark Plugs, I have also seen them on the top of the Water Jacket.
Which Service Manual did you download?

 

[CamelStyle]

70s Era Merc 800 means 1970, 71, 72, or 1978
Before pulling the carbs off did you verify that they were opening fully? BTW, you don't adjust the Cable Length to get the carbs open fully. You adjust the length once the Idle Speed is set.
Now that the Carbs are off, you will need to verify and adjust the Sync between them and the Spark when you reinstall them.
The Teletale connection point has moved around on some engines over the years. I have seen them located on the Water Jacket Cover, near the Spark Plugs, I have also seen them on the top of the Water Jacket.
Which Service Manual did you download?

I’m not exactly sure what year it is. I always thought it was a 1975…but could be 1972?
I had to replace the swivel bracket and the old one had the serial missing. It’s the red band series but the previous owner did some work to the motor so it’s hard to match up. Looks like it the block was painted black. WMK4 carbs.thunderbolt ignition.

I got the service manual from https://www.scribd.com/book/261448610

They looked like they were fully opening, what’s the best way to sync them?

As for the tall tale it’s hooked up from the back of the spark plug plate. Should I keep those 2 “ports” capped then ? Ones on the bottom of the water jacket and one above on the motor by the flywheel in the back like in my picture mentioned

Thanks

 

[CamelStyle]

For reference

 

[jimmbo]

Red Band(s) on the cowl means pre 1972, which means 1968-1971

 

[CamelStyle]

Red Band(s) on the cowl means pre 1972, which means 1968-1971

Interesting. How can I find out for sure ? Previous owner did work to the motor so there’s new and old parts mixed together. Either way I put the water jacket back on cleaned it up.

What should I do with the 2 ports on the top and bottom of the water jacket should I tie those into where the hose goes to the tall tale ? Or loop the bottom and top of the water jacket side together?

 

[CamelStyle]

Also I didn’t pull the jets or anything from the carbs just soaked them and used compressed air. Do I still need to sync them? Found the steps in the service manual seems excessive for just pulling them off

Thanks for the tips

 

[jimmbo]

You have to insure they are both fully closed at Idle, and that they start opening at the proper timing spec, and that they are fully open at WOT
Post a Pic of the Cowl Top and Wrap.

 

[CamelStyle]

Here’s the cowl and wrap and carbs that I cleaned

 

[jimmbo]

1968

Edit: 1969 would have had Merc 800 on the Side of the Top Cowl towards the front. 1970 and 71 would have had 2 thin Red Stripes above and below the word Mercury on the Cowl Wrap

Personally, I think the 68 and 69 Cowl Decals/Graphics are the best Mercury ever had

 

[CamelStyle]

Yeah it says merc 800 on one of the sides.. so is it a 69 then?

What are your thoughts on the 2 fittings should I leave them capped? I’m going to fire it up tomorrow and see if it’s still peeing hot after cleaning up the water jacket. I just didn’t see any water last time coming from the top just the bottom of the spark plug side that’s why I’m curious if they need to be connected but it should feed internally from the one side to the other I noticed on the plate there’s a hole.

I just don’t want to tear it apart again

 

[jimmbo]

1968


1969


70-71


72




You really need the Factory Service Manual to determine where the Teletale gets its water from. I will assume that someone has been in there and added a fitting at the top of the Block, or that was where the Teltale went originally as the fitting at the middle of the Waterjacket cover, was where I would hook up the Water Pressure Gauge Feed. As for the Fitting on the lower part of the Exhaust Cover, I have no idea what that one was about.
Do you have a Serial #, that would direct me to the appropriate Parts List?\

Edit. Checking a bit deeper, it couldn't be a 68, as 1969 was the first yr for the 4 cylinder 800

 

[CamelStyle]

Those all look very similar. Is there a serial number that’s not off the swivel bracket I can find? Since I had to replace that and it’s probably off a 72 that I picked up

Added a pic from before I replaced broken cowl support bracket.

Edit: 6386A4 Mercury 1975-79 & 1985 Swivel Bracket

 

[jimmbo]

hmm, the lower cowl cover is a 70 or 71
Possibly a FrankenMerc

 

[CamelStyle]

hmm, the lower cowl cover is a 70 or 71
Possibly a FrankenMerc

Haha it seems that way. I’m going to try a water trial again tomorrow after throwing the carbs back on and monitor the temp. Hopefully the cooling issue is fixed.

I’ve restored the interior of the boat so I had the quicksilver throttle mechanism taken apart and put it back the way it was but last weekend when I went WOT I was under 2500rpm. With the cables disconnected at the motor I was able to rev the motor way past that.

What should I be adjusting?

Thanks again for the frankenmerc help

 

[jimmbo]

Haha it seems that way. I’m going to try a water trial again tomorrow after throwing the carbs back on and monitor the temp. Hopefully the cooling issue is fixed.

I’ve restored the interior of the boat so I had the quicksilver throttle mechanism taken apart and put it back the way it was but last weekend when I went WOT I was under 2500rpm. With the cables disconnected at the motor I was able to rev the motor way past that.

What should I be adjusting?

Thanks again for the frankenmerc help

Was the engine in gear when you were doing these rev tests?
I will be honest, I don't know why you took the Shift/Throttle Control apart. If you didn't get it back together exactly how it was before... I would be looking at the Control, before trying to mess with the Cable length, as I said above, the Cable length is adjusted only to provide the correct amount of Preload on the Cable at Idle
From what I can see of the Control, it this one. Ignore the yellow arrow, it is there cause I used this pic trying to explain the Captain Overboard Switch to someone



Did you take any part of the Throttle Linkages apart on the Motor itself?

 

[CamelStyle]

Was the engine in gear when you were doing these rev tests?
I will be honest, I don't know why you took the Shift/Throttle Control apart. If you didn't get it back together exactly how it was before... I would be looking at the Control, before trying to mess with the Cable length, as I said above, the Cable length is adjusted only to provide the correct amount of Preload on the Cable at Idle
From what I can see of the Control, it this one. Ignore the yellow arrow, it is there cause I used this pic trying to explain the Captain Overboard Switch to someone

View attachment 386078

Did you take any part of the Throttle Linkages apart on the Motor itself?

I’ll be honest this is my first boat I’ve had seadoos and grew up on ski boats.
When diving into this project I didn’t have any clue what I was doing engine wise but I’ve rebuilt motors and done other projects with success.

When I first got the hull and motor i was able to fire it up so I concentrated on the interior and structure. I built a new transom so I pulled the motor and figured disconnecting the cables from the shift throttle control box would be easier than from the motor. Long story short I ended up tearing the whole motor apart just to replace the swivel bracket and then re wiring and other general stuff.

But while pulling the motor, I broke the shift linkage on the motor. Fixed that.. but had to take the cables off I marked them and put them back as it was.

Last week I got everything back together as it was when I got it. And here we are now.

- couldn’t get past 2500rpm with cables connected
- tall tale stream is strong but very hot I’d guess over 140f (I will bring a IR thermometer this time)

Otherwise it starts on a dime. Looks like previous owner rebuilt the innards.. rods,seals, etc

 

[CamelStyle]

So I fired it up in my barrel and after 5 mins at idle
I’m at 145-155f

Got into the liquor last night so I had a late start but with the carbs cleaned seems to be running great