94 115 V4 crossflow stumper!!

Hope I'ts ok for me to post this in here, my boat is actually a Four Winns fling with OMC jet drive, but everything I have researched says the motor isthe same as Johnson-Evenrude and I figured I'd get better response here. So anyways I'll try and keep this as simple as possible.

Boat sat for 2 years, start for first time, starts real hard but get it going and after a little warm up time she runs pretty good. I play around for about 5 minutes, spin the boat around, drive lifts out of water, engine free revs for a second and just stops! I let it set for a second, turn the key and it fires up, put it in gear start moving forward and the warning buzzer goes off, overheated?? So I idle for a minute and the buzzer stops, try to accelerate and it will only go about 1/3 throttle and bog out, so I limp it back to shore having to go back to idle a couple times to kill the buzzer. I bring the boat home, do a compression test and get;

115 122
110 105
Looking from back of motor.

Pull heads and # 1 (with most compression) has some minor scuffs, all others look great.
Install new head gaskets, new compression test;

106 122
105 106

try to get it started and it tries and tries but will only fire for about 5 seconds then quits, sometimes with a cough, or backfire, acts like it isn't getting fuel so I put some pre mix in spayer, remove airbox and spray directly into carbs when trying to start, doesn't really help, so go other direction and no spray no primer, won't fire at all.

Here's were it gets interesting, my kid says lets check spark, so I pull #1 plug, set on head and tell him to hit the key, the damn thing fires right up and runs!!! Put it back in and same ole crap, fire's but won't start. So I try pulling another plug, and sure enough it starts and runs. I don't get it, why will it only run if I remove a plug, any plug????
Please Help!!

Re: 94 115 V4 crossflow stumper!!

105 views and no comments, guess it is a stumper :facepalm: At this point I'll take wild guesses! I'm running out of ideas and really want to get on the water this weekend. I've been wrenching for almost 30yrs, not many outboards though, and can usually figure things out, even if at trial and error, but this one has me, what am I missing???

Re: 94 115 V4 crossflow stumper!!

Did you check for spark and all connections , maybe the flywheel sheared a key, causing it to be out of time. I have some issues with my 115 it intermittently runs on 2. I need to do some digging around as well.

Re: 94 115 V4 crossflow stumper!!

How fast is the mtr spinning over when trying to start it ?? Should be around 250-300 rpm. As a wild guess I'd say you might have a bad power pack.

Re: 94 115 V4 crossflow stumper!!

Checked the flywheel key, good, #1 piston tdc at index tdc. I did find that some wires to the fuel pump had gotten hot and melted the casing and someone taped them up (from a previous overheating I presume) but no copper showing. My mission tonight is to trace all wires and check for melting or grounding. As far as rpm at start, it is a new battery, but the starter does seem to kick back out a little too soon in my opinion?? Maybe it isn't spinning fast enough, maybe when I take a plug out it releases enough resistance to spin faster?? It is a 600 cca battery, maybe I'll try my neighbors 850 and see if it spins faster. Any hints on how to check power pack??
All help and idea's are greatly appreciated!
Propmonster

Re: 94 115 V4 crossflow stumper!!

Does it start if you just remove the lead from a spark plug, or does it only start if a plug is removed thus increasing starting rpm? IMHO, that would separate the decrease in startling current load from the issue of low spark voltage with fewer plugs trying to fire. Just a random thought about starter rpm/current vs a power pack/spark issue. At least you found a way to get the thing started. Looking forward to seeing what resolves the problem!

Re: 94 115 V4 crossflow stumper!!

Really leaning toward an ignition issue at this point. Could the free rev fried something?? because after that it did start, but it would only go about 1/3 throttle and was running rough, at that point I assumed a head gasket blew because shortly after that the buzzer sounded and it was hot (steam off top of heads). I did do a compression check before changing head gaskets and after, I did not seem to gain any compression on any cylinder, so the gaskets were probably not blown. Stuck rev limiter?? Is there some kind of safety ignition detent?? Anybody wanna buy a Jet Boat!! :facepalm:

Re: 94 115 V4 crossflow stumper!!

Success !! For those of you not familiar with the turbojet, there is an exhaust manifold on the bottom of engine that exits through a 2 1/2 " rubber hose that goes up into a U and back down to the drive where it exits boat. Well this U had gotten soft and the inner layer collapsed causing a back-up of exhaust that over time let about 12 oz's of sludge to build up in the lower manifold and almost completely block the exhaust. Therefore when I was trying to start it was creating too much back pressure, and that's why when I removed a plug it gave the exhaust a release port. Starts right up and runs in the driveway, headed to launch it right now, wish me luck!! Thanks for the suggestions guys........