Engine on a 170

[Miguel]

I´ve been away from the forum for a long time, due to various reasons.  I have also been away from boating.  But fortunately I hope to be coming back soon, so HELLO AGAIN!
A week ago I tried to start the old 115 Mariner and it started giving all sorts of problems.  It only has spark on two of the four cylinders.  One power pack later, problem is still there.  As usual with ignition problems, the mechanic is guessing and I just received a new trigger which is waiting to be installed.  In any case,  I'm considering a repower.
Has any of you repowered a 170 or 175 with one of the four strokes, say 90hp or 115hp?  The Yamaha 115 4s is about 40 pounds heavier than my current engine, and my scuppers are currently underwater anyway.  I have some experience with the Yamaha 4S and really like them due to their fuel economy and quiet operation.  
I know the subject of power on this boat has been already touched upon, but I'm very interested to see if anyone has experience with these setups.  Any thoughts?

[RickK]

Hi Miguel - welcome back    Been wondering where you've been.
Sorry to hear about your engine, been sitting a while eh? I bought a rebuilt powerhead for my engine and am going to install the "new" engine when I'm done with the rebuild of her.

[Miguel]

Well, the engine had been sitting for about 8 months.  I'm fixed on the idea of getting it repaired, but I understand that it may be time for a repower.  I just wonder if the additional 40 pounds of the F115 will make a big difference.  I do not want to downgrade to a 90, because I feel that this boat's sweet spot requires a 115.  The problem I'm having is that in Panama, the only 115 2 strokes still available are the Mercury Optimax's.  I´m fed up with the Mercury/Mariner electronics and the fact that there is one single dealer.  Yamahas and Suzukis  have really taken over the market.  
If and when I get the old one fixed, I'll take a little ride with a couple of 5 gallon buckets with about 8 gallons of water on the stern.  I'll throw a little bit more weight to compensate for not being able to place it farther back.  That should give me an idea of what to expect with the heavier motor, dont' you think?
In any case, I´m still waiting to hear from other 17 owners that may have the same setup.  None?

[RickK]

While you're waiting, how's the new canal coming along?

[Miguel]

It's coming along... But it is a big job and there is still a stretch ahead.
More than 3 million cubic meters (that´s about 4 million cubic yards for you) of concrete have been poured already, and we just received the first shipment of 4 gates (roughly 3400 tons each).  It keeps me busy, I tell you... I believe there are some photos and videos at micanaldepanama.com

Now, how come I can't get the damn motor fixed?  It certainly appears as if good outboard technicians are scarcer than nuclear physicists...

[GoneFission]

It's coming along... But it is a big job and there is still a stretch ahead.  

It certainly appears as if good outboard technicians are scarcer than nuclear physicists...

I believe that is true...    

[slvrlng]

Welcome back Miguel! Have you checked the compression on all the cylinders yet? To have it running right on your motor you will need at least 105 to 110 psi on each. It will run below that but not as efficiently. Compression check is easy to do with 2 people. Please report back with what you find.

here is a youtube link on how to do this procedure

http://www.youtube.com/watch?v=eSmNMWTDtZE

[Miguel]

I have not checked compression, but the last time I used her, she was running perfect.  In any case, I know for sure that there is no spark on the upper two cylinders.  With these Mercury/Mariner's you learn to start by checking for spark...  In my experience, they are plagued with ignition problems.

[Miguel]

As it turns out, the trigger was bad.  Just had it replaced and now it fires right away.      

[RickK]

Good deal - hey, don't be a stranger, you have a lot of experience to share.  

[Miguel]

I'll certainly try to keep in touch, Rick...
I've been following your rebuild and have a lot of curiosity to see the finished product.