head gasket/spark...200 Mariner

**Jobu68** · 07-21-2009, 07:50 PM

I have a 98 Mariner 200 2.5 and after correcting a water circulating problem, I have isolated a problem down to no spark or head gaskets. The top port spark plug looks clean, like brand new and I am going to first do a spark test and go from there. I bought a tester that the plug wire goes over and then the alligator clip clips onto the block for grounding. Does anyone know where to clip it on the block (thinking its aluminum and not a great conductor)?
2 after a compression test and if it's getting spark(bought a coil just incase), could anyone tell me any info they think will help in changing a head gasket? I know it's 30 psi on the torque wrench...is there any cement or grease used or just compression...what's a good method of cleaning old gasket...should it just come off after all bolts are removed?
I'm a total nube at this but have some mechanical expirience.

The original problem was I think corrected. It was barely pumping water and it would come out intermittantly. I put in new stats, impeller and housing. It pumps alot better now but I am getting water out of the propeller. (normal?) Now the problem is it runs rough during acceleration and tops out at 4700rpm not 5600 like before.

Brand new to this forum...someone from Classic SeaCraft sent me here.
Any help is welcomed.
Thanks,
Joe Reen

**Jay Smith** · 07-21-2009, 08:08 PM

Hi Joe welcome to Scream and Fly.......
You can hook your ground to any metal bolt or bracket to use your spark tester. Also to torque the heads I start off at 20-25 Ft lbs and go through the sequence start in the middle and work outwards in an X patteren making the X larger and larger.... I next re run the torque sequence at 38 on high performance engines an 35 FT on motors like yours. I use NO sealer on the gasket just make sure both surfaces are clean and free of debree...I use grease on the male bolt thread and light oil on the bolt flange to insure proper torque value... I DO NOT SUGGEST using the 30 lbs + 90 degrees like is on the heads unless you choose to repair LOTS of stripped female block threads...

Thats the way I do it,
Jay

**beamrverbeek** · 07-22-2009, 12:12 AM

alloy not a good conductor????? the service wire coming into your house is all alloy.

welcome aboard

**sxmerc** · 07-22-2009, 06:21 AM

As far as cleaning the head gasket, you want to use a razor scraper to remove as much gasket as possible. After that I like to use the 3M Roloc surfacing wheel to get the surfaces real clean. These wheels aren't as aggressive as some of the fiber resurfacing wheels,so you're less likely to grind to deeply.

**Jay Smith** · 07-22-2009, 09:59 AM

Thats works for me....

Jay

**Jobu68** · 07-22-2009, 06:27 PM

Thanks guys. I will poke around out there tonight after supper. I was planning on pinchin the fuel hose to run the compression and spark tests.
How many revs should I do on the comp and how many psi should I be expecting?
Thanks again,
Joe

**sxmerc** · 07-22-2009, 07:18 PM

Three or four revs should be sufficient. Gauges vary but usually 125 to 140ish. As long as they're all within 15% of each other basically.

**Bartman39** · 07-22-2009, 07:32 PM

Also if no spark then it may not be a coil issue either... Most of the time when there is no spark on one cylinder it can be a bad switch box... A fairly easy and simple way to tell is switch wires on the coil right beside it and see if the miss moves with the wires... If it does then its more likely a switch box and they should be changed in pairs... Although I keep a good single just to test with and buy a new pair when needed...

If its a head gasket the compression test will show for sure then a good inspection of the bore after the head is removed will tell you if a simple replacement of the gasket will work or if an in depth repair is needed...

Also is this an EFI motor or carb...? If its EFI then just unplug the ECU so the injectors dont fire also the EFI wont run... A little different with a carb motor...

**Jobu68** · 07-24-2009, 07:36 PM

Its a carburated motor.
I'm gonna try first thing in the morning. I noticed there was water coming out of the prop hub when I ran it on muffs...is that normal?
Joe

**sxmerc** · 07-25-2009, 06:30 AM

Water out of the prop hub is completely normal. Actually, I would be concerned if there were no water exiting there. This is the main exit for exhaust and water.

**Jobu68** · 07-25-2009, 12:02 PM

Here are my results.
cold comp test
top to bottom port 94, 101, 103 psi
top to bottom strbrd 93, 102, 104 psi
head gasket?
out of ideas.
all six cylndrs have spark...top port plug is cleaner than rest but shows some sign of ignition.
???
Joe

**Jobu68** · 07-25-2009, 05:30 PM

The gasket looked frayed around the cylinder opening (new gasket has a metal ring but old one was tattered/ jagged around all openings also I see no metal left). There was a little bit or corrosion/salt between the water jacket opening and the top cylinder.
Also signs of salt inside the head walls...normal?
The top piston has some minor scratches dings in it as does the head in chamber. I'm thinking when the ring disintergated it got chewed up in the combustion chamber...?
As far as I can tell the cylinder walls look scratch free. Pistons have alot of carbon soot but other than the dings they look to be in tact...not new but decent.

Going to put it back together and have a look at the starboard side.

thanks for the info...I listen to it all.
Joe

**Bartman39** · 07-25-2009, 07:59 PM

While the compression sounds low they are not to far apart for it to run ok but a leak down test is needed for sure... If a head gasket was leaking compression you would not see numbers that high... As for the dings and such it may have been from an old blow up and if were a ring destroyed you would not see much compression either...? Do you know the history of the motor...?

I would put new head gaskets on it for sure and trace down the coil wiring to the switch box it connects to and change it with a known good unit to test with and if it fixes the problem then put 2 new matching switch boxes on it...

**Jobu68** · 07-25-2009, 09:44 PM

Thanks for the reply Bartman.
It looks to me like the rings on the gasket broke up and got mashed up in the cylinder. I replaced the port gasket today and will do the right side tomorrow. I don't know much of the history but the gaskets did show some sign of letting water into the cylindar judging by the traces of salt left underneath.
After the other gasket is installed I will run a copression test and see. The spark test I did earlier was positve on all 6.
The only thing I did notice was that the prop had a lot of slop in it so I pulled it and it was loaded with with monofillament. the rubber bushing was actually wearing out in a diamond pattern so I will swap it with a new prop tomorrow too. It was so bad it had about 4 degrees of slop...it had to have been contributing a little to the problem.
It has a 15.25x15" now and I was thinking of going a little smaller diameter and larger pitch to get a bit more top end. The motor is on a 23' SeaCraft Scepter which is a little heavy for a 200 but has great out of the hole power but only 34mph top so I hope to gain a little by pitching up....Thoughts?
Thanks again for your help, this has been a great forum for me!
Joe

**Bartman39** · 07-25-2009, 10:52 PM

Could possibly be the sealing ring of the head gasket...? Never seen that before but hey in salt water anything is possible to see...

As for the prop going to a smaller diameter like a 14.25 and up maybe 1 pitch would be do-able but any more and it might lower the RPM`s to much and kill the hole shot...? Cupping will also be a factor, if its alot of cup it will lower the RPM`s but dig harder out of the hole... Keep the RPM`s in that 5500 range and the motor will live longer too... For more speed either a bigger motor or smaller lighter boat just the nature of the beast...

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