Mercury 115 Powerhead Blown

[gregdan24]

This is my first post here, so first an introduction, I am from SW MI and have owned my 1988 Fisher 18FS with a 1988 Merc 115 L6 since new. I have run across this site a few times when searching the web for info and appreciate all the advice you folks give to those in need. I hope someone can help with my questions.

Last year my motor lost a couple of cylinders - no compression. Not sure exactly why, but it had problems for about 4 years and I tended to run it pretty hard. So, live and learn - and slow down. While searching for options, I ran across a used powerhead at a local dealer. The lower unit on this motor was trashed. It doesn't have a sticker, but based on the stripe colors, etc., it appears to be an identical match to mine and looks to be in good shape. They are going to pull it out of storage, check the compression and call me. The problem is they are asking $1,200 for the powerhead only, which seems a bit high. The other problem is, even at this price I don't thing I can get power on the back of the boat for less. Remans look to be nearly $2,500.

Can anyone tell me what price range one could expect for good used powerhead? Thanks in advance for any advice/experience. -Greg

 

[Bob_VT]

Re: Mercury 115 Powerhead Blown

You have a PM

Welcome to iboats!

 

[Faztbullet]

Re: Mercury 115 Powerhead Blown

Thats way to much for that powerhead !! You can buy a whole boat ready for the lake with same motor as you have for $1600.00
http://nashville.craigslist.org/boa/1008198074.html

 

[sschefer]

Re: Mercury 115 Powerhead Blown

Can anyone tell me what price range one could expect for good used powerhead? Thanks in advance for any advice/experience. -Greg

Greg, I would save your money and get something that you can see running. If you run them hard then there's no room for a storage room powerhead in your life. A rebuilt powerhead can be a hit and miss thing. They all offer a money back guarantee but they won't pay for your labor or you lost boating time.
If you are mechanically inclined enough to replace a power head you should just rebuild the one you have if it's not too far gone. Otherwise, do like Faztbullet say's and start watching Craing's list for a complete boat and motor. Keep the motor and sell the boat with your bad motor on it and not only will you get your old motor hauled away for free but you might even get some cash out of the deal.

 

[gregdan24]

Re: Mercury 115 Powerhead Blown

You guys have given me some great advice. I am now leaning towards a diy rebuild. I've rebuilt other motors (MC, jetski) but was a bit leary of this one because of the ring compressor set required. But today I had a chance to talk to my buddy (he's about 90...smart guy) who works for his brother who owns the small marina about 4 doors down from my house (I know, why didn't I go there first you say...). And there's a guy less that 20 miles away that does marine machine work. So I'm going to tear it down and see what I have, bore/re-slug the cylinders that need it, deglaze and re-ring the rest. He'll let me borrow the ring compressors - or I'll likely walk it down and let him do it for the price of a nice dinner out. So if all goes to plan I should get out of this for a little more than half the price of that used powerhead...a much cheaper experiment! I have a Seloc manual that seems pretty good. I would be grateful for any tips on other things to look out for when tearing down and inspecting. Thanks again folks! -Greg

 

[gregdan24]

Re: Mercury 115 Powerhead Blown

Thats way to much for that powerhead !! You can buy a whole boat ready for the lake with same motor as you have for $1600.00
http://nashville.craigslist.org/boa/1008198074.html

Man that motor looks good in the pic. I'm just about tempted to give the guy a call and buy it! Would cost me about $250 in diesel to make the round trip though. That bass boat would probably be a nice little rig on the lake I live on too.

 

[Chris1956]

Re: Mercury 115 Powerhead Blown

Greg, Merc uses a set of specialized ring compressors to install all six pistons, which are connected to the crank, all at once. When I rebuild my inline six, I remove all the connecting rods from the crank, and put the roller bearings and cages into a dixie cup marked with the cylinder number. I then bore or hone the block, and install all the pistons into the bores. This can be done with your fingers or a screwdriver. Now install the crank and individually stick the cages and roller bearings onto the bearing surfaces with grease, and install the rod caps, one at a time.

This method takes some extra time, but it can be done by one person, and doesn't require special tools.

BTW, You need to fix the cause for your engine to need a rebuild. That means clean and rebuild all carbs, rebuild the waterpump, rebuild the fuel pump and do a link and sync on the motor. if the motor overheated, it is likely that number 1 and 3 cylinders took a beating, and are the ones w/o compression.

 

[gregdan24]

Re: Mercury 115 Powerhead Blown

The bad cylinders are 4 and 5. I rebuilt the carbs year before last and the water pump last year (stupid me the one in there was the original...). Still need to rebuild the fuel pump though. I really appreciate the tips on getting the pistons in separate.

Here's the kicker...the shop called me on the used powerhead and said the cylinders were scored so they bored and put new pistons in it. 5 are .015 over and 1 is .030 over. Said the crank and rods are good. Still $1,200 to me though. Not a complete reman but better than used. Thinkin' I shouldn't pass up that deal given my powerhead is an unknown. Another decision to make.

When boring oversize is there any rejetting needed? Wouldn't think so as the compression should go down. So if anything it would run a little richer at WOT?

 

[Chris1956]

Re: Mercury 115 Powerhead Blown

Greg, The change due to boring is so small in comparison to the displacement of the cylinder, that it makes no difference in compression or jetting. The oversize pistons weigh the same as standard pistons, so you may mix and match.

 

[gregdan24]

Re: Mercury 115 Powerhead Blown

Thanks Chris, you have been a great help.