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Conference vicki::boats

Title:	Powerboats
Notice:	Introductions 2 /Classifieds 3 / '97 Ski Season 1267
Moderator:	KWLITY::SUTER

Created:	Thu May 12 1988
Last Modified:	Wed Jun 04 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	1275
Total number of notes:	18109

1110.0. "POWER LOSS PROBLEM HELP FOR AN OMC 115 HP OUTBOARD" by POWDML::TARRASKY () Wed Sep 08 1993 16:57

    My Peer Weekend Mechanics, 
    
    HELP! I have a 1984 VRO (disconnected) 115 HP OMC Outboard that has
    developed a loss of Horse Power problem (almost unable on cold starting
    to get the 16 1/2' Wellcraft Bowrider on plane, after running 20 mins.
    or so, can't continue nor again bring it up on plane [makes me think of
    things electronic/electrical that heat up and fail], all while at full 
    throttle while pouring excessive fuel thru the motor, I know,  due to 
    the fuel missing from the tank after several attempts to fix the problem).
    The sound of the engine is less powerfull in tone, but no skips, cut
    outs, backfires, or misses, while revs seem up to what they were (I don't
    have a tach - so all I can do is use my senses which may be faulty), and 
    she idles beautifully while the plugs all seem a bit wet and are black.
    
    The problem began after I replaced my Power Trim and Tilt Unit which
    failed the previous weekend after 6+ solid hours of running fantasticly
    as it has all season. The replacement shook the motor for over 1 hour
    due to having to hammer out, after heating the tilt pin area of the
    lower unit housing with and oxy/acetylene torch, with a 5 pound sledge
    and drift (corrosion ate a hole in the PT&T aluminum manifold after
    being in/below the salt water line for the past 7 years). I checked the
    compression (to make sure that was not an issue) at 120 - 130 PSI, the
    advance and timing with a timing light - OK, all electrical connections
    of which some were moved due to unplugging and reconnecting the PT&T
    and Tilt Position Switch wiring - OK to look and feel, and I took the
    carbs both off and went thru them last night hopping for some foreign
    matter that may have been dislodged in the high speed jet/venturi area,
    or even a float/needle/valve seat problem - no luck. So, that seems to
    target the C. D. Ignition System area and the dual Power Packs before
    my call to OMC Backup support at the Factory (they like you to have run
    all the checks with their equipment before bothering them). 
    
    Who would like to venture a guess at what should be looked at first,
    and if it is an ignition problem, in your opinion. I have late 60's
    and early 70's OMC training and experience, prior to the C. D. Systems,
    and do not ever remember running up against such a problem, and on my
    own boat. I have eliminated the PT&T, powerhead mechanical, fuel system, 
    and timing advance to the extent posible that I could check with the
    timing light, in my mind as the problem. And, electronic stuff is both
    expensive and non-returnable, so I want to be as close to being on
    target as possible. So, here is your chance to tell me where I may have
    gone wrong or what I may have missed. Your inputs, please.
    
    REGARDS,                              
    
    Mike

T.R	Title	User	Personal Name	Date	Lines
1110.1	I had a very similar problem...	LJSRV1::64691::THEMAC::Boucher		`Wed Sep 08 1993 17:34`	16
	I had a very similar problem with my '78 115. Seems that it would rev up but just didn't have the power it used to and it seemed that I was only running on 2 cylinders. The way I found the problem was after running about 5 minutes I stopped to check the plugs. I pulled all 4 but while pulling them I realized that 2 were very warm and two were completely cold. I then put a new pulse pack on the side that was cold and the problem went away. The engine has been running like a top since. The reason I had an extra pulse pack was that I was doing what you are doing in trying to diagnose a problem and thought it was the pulse packs. If you could just borrow one from someone and give it a try that might be a nice quick ($$) find. Anyway just some of my thoughts. -Matt
1110.2	EXCELLENT DIAGNOSTIC TECHNIQUE & EXPERIENCE, MATT	POWDML::TARRASKY		`Thu Sep 09 1993 11:29`	7
	Great thought and diagnostic technique - cold plugs vs. hot, Matt. It seems to me that the engine was still relatively cold after running it for an hour or so, and I will try to conjure up another pack for my weekend pilgrimage to the mooring to fix it, esle I'll buy a good used one to have to try (I always buy used first, if available). Thanks! Mike
1110.3	A long shot	GUCCI::HERB	Al is the first name	`Thu Sep 09 1993 15:59`	5
	I had an early 70s Evenrude 70HP (3 cyl/3 carb) with a power loss problem. It turned out that the carb gaskets had dried out and lost their seal. Basically, you could manually engage the choke and it would pick up power. The vacumn leak was preventing suffient vacumn to draw gas from the fuel bowl.
1110.4	Thanks for the thought, Al.	POWDML::TARRASKY		`Thu Sep 09 1993 18:16`	5
	Thanks for the thought, Al, and I will enruse no leakage when I put the carbs back on this weekend with new gaskets. Real inexpensive insurance to finish the reinstallation. Mike
1110.5	I had one more thought	LJSRV1::64691::THEMAC::Boucher		`Fri Sep 10 1993 11:17`	15
	Mike, I also had a wire going to a powerpack break (read as wore out) It was one of the wires that was attached to the thing (can't remember the name right now) that advances the timing when you throttle up. Apparently the moving of the wire over time wore it out and all I did was solder a new wire in and I was back in business. The way I found this out was I put my timing light on each spark plug wire and found out that only 3 of 4 spark plugs were actually working. Then I did the standard tests in the OMC manual about checking the wiring harness and found the wire no problem. Just another thought, -Matt
1110.6	Left cylinder bank power pack gonezo, FYI	POWDML::TARRASKY		`Mon Sep 13 1993 12:50`	27
	Matt, Your suggestion seems to have hit the mark, as of 8:10 PM last night, under the stars, the problem has gone away with the replacement of the left bank power pack. A B I G T H A N K Y o u to you Matt, for lending the experience, knowledge, encouragement, and direction to pick up the used power pack. After reassembly and no better performance, I looked at the plugs and found the left cylinders a bit wetter than the right ones, and replaced the left one, temperature was about the same for all of them though. I do now note a much higher pitched exhaust note at fullthrottle running than in the past and lower engine temps, so, the loss of power must have been occuring over some time and until the fata accompli, which I feel may have been excelerated by all the additional heavy hammering vibration that put it away for good. I still have to admit that the C. D. System and dual packs gives stranger and more difficult to pin point problems than I have ever experienced the feel of in diagnosing. And, having a good assortment of electronic parts available to substitue or the OMC or aftermaket testing tools, other than the trusty old volt ohm meter, seem essential when experiencing such difficulties to resolve. Six cylinder outboards must be real fun to work on these days! REGARDS, Mike
1110.7	How to Compression test?	BUSY::CLEMENT	Smells like Nirvana	`Mon Sep 27 1993 12:00`	20
	Instead of starting a new topic I figured I'd use this one... General question on procedure to check compression. Can this be done with the outboard NOT in the water? I can see no reason why we would need cooling water since the engine will not start with all the plugs out. Procedure: Remove all plugs, for each cylinder: insert guage, crank, record reading spray some oil in cylinder and repeat above. If 2nd readings vary largely (rise) indicates worn rings. If first and 2nd readings are too low, then indicates valve problems? Thanks, Mark
1110.8	The impeller rubs the housing at low speeds	ROBOAT::HEBERT	Captain Bligh	`Mon Sep 27 1993 12:12`	3
	Water lubricates and cools the impeller in the water pump. Anytime that puppy is spinning it should have water supplied to it.
1110.9	2-cycle engines don't have 'valves' as such ...	11SRUS::FYFE	United We Stand America - 800 283-6871	`Mon Sep 27 1993 13:19`	36
	> Procedure: > > Remove all plugs, for each cylinder: > > insert guage, crank, record reading Keep the throttle wide open when doing this. > spray some oil in cylinder and repeat above. > > If 2nd readings vary largely (rise) indicates worn rings. Not necessarily. A cold engine will read lower than a warm engine with a more dramatic increase in compression when adding oil to the cylinder. Best to start this operation with a warm engine. Also carbon build-up, common to many 2 strokes can affect a rings performance. Once removed the rings will will function better. There are products on the market to help remove these carbon deposits. > > If first and 2nd readings are too low, then indicates valve problems? A 2-cycle engine has reed-valves which do not affect the compression stroke of the piston. In general, if compression is low the culprit will either be rings or head gaskets. The OMC 115 power head was manufactured for several years with a (now) known defect. Excessive space is worn between the piston and the cylinder until there is enough room to suck in a ring. The only true fix is to rebuild the power head with sleaves and new pistons. OMC, and many others, sell a kit just for this purpose. I have a powerhead waiting for just such an operation. Doug.