Smoke out the telltale!! Mercury 9.8

[Rodman738]

Recently purchased a 79 mercury 9.8. Motor will start,smoke will come out of telltale for a few seconds when water starts coming through telltale engine will stall! I'm no mechanic but I'm thinking I have a bad gasket? Just wanting a second opinion thanks. Love these Darn Mercury's!!

 

[Scott Danforth]

exhaust cover gasket would be my thought

 

[Scott Danforth]

nice looking Hellion in your pic

 

[Rodman738]

Thanks Scott! Hopefully I can get this Mercury running and get it back on the lake. I will probably just get a gasket kit . Probably as soon as I replace one another will go. Thanks for advice!! What kind of speed did you get out of your Hellion with 9.8? My Johnson overheated but I got 21 mph with it.

 

[Sea Rider]

Being such an oldie, replace head and exhaust gaskets, take advantage to decarbon piston heads, exhaust chamber and cylinder head, ckeck/replace thermostat/gasket, water pump's liner/impeller condition. Clean all water passages...

Happy Boating

 

[racerone]

??----There is no cylinder head on that 9.8 motor !-----There may not be a thermostat either.

 

[Scott Danforth]

Thanks Scott! Hopefully I can get this Mercury running and get it back on the lake. I will probably just get a gasket kit . Probably as soon as I replace one another will go. Thanks for advice!! What kind of speed did you get out of your Hellion with 9.8? My Johnson overheated but I got 21 mph with it.

I never finished it, sold it as a project the day after I installed the '85 electric start 9.8. the guy that bought it, said he hit 27.

I did make a custom set of mini trim tab for the boat. basically a half-scale set of bennet sport tabs. used turn-buckles for the actuators, however had found small hydraulic cylinders if I wanted to power them.

 

[MTboatguy]

I don't have a "Head" on my Merc 110, the plugs screw into a cylinder and there is a block cover that goes over it, which is part of the water cooling system. Many confuse this part as being a "Head" but it just contains the water.

It does not have a thermostat either..

 

[Rodman738]

The compression is around 110. With motor tore down for gaskets would it be wise to put new rings or anything else?
Thanks for all the great advice!

 

[MTboatguy]

Rings are not that expensive so if you have it torn down that far, no reason not to, check the cylinder walls for scores or a lip at the top to make sure it does not need to be bored out a bit. That said, my 110 runs about 110 on the compression test and I have never had any problems with it at all, so that is probably an "at your discretion" type situation.

By the way what is the serial number on this motor?

 

[Rodman738]

serial number is 5317208. I guess when I get it apart I can decide what I need to replace. Hopefully it doesn't need bored!
I wonder if gaskets drying out on these older Mercs is a common problem. I guess I can understand why on a 40 year old motor. Thanks for your comments!! Love these Old Mercs!!