225 Ocean Pro compression check

2000 225 Ocean Pro. Is there something I can unplug to disable the ignition system to do a compression check? Or do I really need to go through the hassle of grounding all the spark plug leads?

No need for the ignition switch to be on.

Using a small jumper, connect from the large battery cable terminal of the starter solenoid to the 3/8" nut terminal of the starter solenoid (Not The Ground 3/8" terminal). That'll crank the engine over with "No" ignition.

BTW.... In my 38+ years, I never bothered to ground a spark plug wire when doing any test... and never had a problem of damaging any components. I did start one hellava fire one time though with all that fuel shooting out the cylinders.

How about those dummy welders that burned up the St. Clair in Toledo? Probably sparks ignited the rubber conveyor belting dust. The last overhaul we did on the Blough, they started 3 fires, one welder died. Always have a fire extinguisher within reach.

Only reason to ground leads is to ...1)prevent a flash fire from fuel expelled from cylinders 2) contact with high voltage. It will not damage components.

Thanks a bunch for the info. guys! I'll be sure to be careful. This boat is new to me and had been sitting a while. On the sea trial the engine ran smooth everywhere except from about 1100 to 1700 rpm. At those rpms it had quite a bit of shake. Once past that it smoothed right out all the way to around 5400 rpm.

Since then, I did a bunch of preventative stuff: plugs, fuel filter, thermostats, cam follower roller, enrichment rebuild, link and sync and idle/WOT stop adjustments. Now it does the same thing only worse and over 2000 it feels like it now has a miss all the way up to 5000 rpm? Trying to figure that out, so I figured I'd do a compression check before I go any further.

The engine fires right up with a short push of the key for enrichment now and it seems to idle good. It does not cut out and idles nicely in gear. Once over 1000 rpm is when things get weird...

joereeves said:

No need for the ignition switch to be on.

Using a small jumper, connect from the large battery cable terminal of the starter solenoid to the 3/8" nut terminal of the starter solenoid (Not The Ground 3/8" terminal). That'll crank the engine over with "No" ignition.

BTW.... In my 38+ years, I never bothered to ground a spark plug wire when doing any test... and never had a problem of damaging any components. I did start one hellava fire one time though with all that fuel shooting out the cylinders.

Click to expand...

I'm finally doing this today. I'm a little confused on which wires to jump? I'll be using a remote starter button. Big one from battery on right with 2 small red wires on same nut. Then the small yellow with red stripe, then a small black wire and then the big red one going over to the starter... Here is a pic of the area.

On the solenoid, jump from the rubber boot terminal to the smaller yellow wire.

The little black wire is a safety to ground which won't allow starter activation unless its grounded. Your switch will go between the large red (with the 2 little reds) and switch to the yellow/red little wire on the small solenoid post. This will let you spin it over.
Ps. Hi Joe!

Thanks guys! I'm going to go warm it up and give this a go...

I managed to get it done. But, not sure how accurate it is. Starter Bendix is acting up and I had to partially crank multiple times per cylinder. I just kept cranking on each cylinder until the pressure on the gauge quit rising.

Port side top to bottom: 98, 100, 90
Starboard side top to bottom: 105, 100, 94

Plugs are brand new. I noticed also that the cylinder that is reading 90 (bottom left), that spark plug is a little darker than the rest. Pic of the plugs below. The bottom right plug is the one that came out of the bottom left cylinder.



Things I noticed are the engine fires right up cold with just a quick push of the key. Not throttle needed at all. It fires right up, first time, everytime. Once the idle settles down there is a bit of a shake. I'm new to these engines, so I'm not sure how smooth they are supposed to be. Also, when going to get on plane there is a bit of a miss and it's there throughout the entire RPM range. After 4,000 RPM it's hard to tell. It will run all the way up to 5400 RPM the way it is.

I'm trying to figure out where to start troubleshooting? Ignition or carbs? I got a feeling it's an ignition problem... Not sure at all though.

I can post a video of the engine running at idle if that helps?

The bottom cylinder on a V-6 are always lower due to head cast at angle, they have lees compression due to exhaust runner length. Your results look OK for starboard side but inspect of port side #1 and #6 needs looked at. #6 is the trash cylinder

Your readings are a bit low overall as well, but could be due to the cranking speed or the compression gauge. I regularly check my compression gauge with my air compressor and keep the oil cleared out of the hose. It has a bleed just below the gauge. That miss at higher speeds could be intermittent loss of spark due to a final coil, or wire defect. At high speeds, the plugs should be consistent in color. If running at low speed/idle/trolling, it may produce some variance. This is assuming carbs are synchronized. At low speeds, depending on air flow, the stale air hovering around the motor may affect the mixture. Air intake locations vary and some designs are more susceptible.

Hey guys. Thanks again for the input! Boat is new to me. When I sea trialed the boat it ran fine (about a month ago). It had a bit of a shake from about 1300 to 1800 RPM. But, after that it was smooth. No miss at all. Since then I did what is listed below and had it out only one other time to check and be sure everything was OK. After I did what is listed below, the miss appeared. Should have just left the damn thing alone.

Because the boat had not been used regularly I took it upon myself to do some preventative maintenance. I changed out the thermostats, engine mounted fuel filter, replaced the plugs, gapped the plugs at .030, replaced the cam follower roller and adjusted that gap to .005, carefully synced the butterflies on the carbs, adjusted the idle and WOT throttle stops and checked the adjustments on the throttle linkage per the manual. It does start very easy and settles down into a nice idle with a little bit of shake. But, again, not sure what is normal on these big V6's.

The carbs are not leaking and everything looks good there. I have not touched them except for the sync.

When I pulled the plugs to do the compression check, I ohmed out the plugs to be sure I did not get a bad plug. Maybe I should try putting the old ones back in? Or maybe I damaged a wire removing the old plugs? Should I try ohming out the plug wires too? Or is the wire on these part of the coil (on the coil end).

They run better gapped @.035

Thanks! I plan to take it out later this afternoon again. I moved that dark colored plug from the the bottom hole to the one just above and it seemed to run a little smoother? I'll gap them all to .035 before I take it out today. I'll also check my cam follower gap adjustments again. I plan to take my timing light and check the idle timing while I'm out there.

Thanks again to everyone who is helping me try to figure this out. I cannot thank you enough. Fingers crossed...

Too Tired to take it out today. I regapped the plugs to .035 and checked the cam follower adjustments and butterfly adjustments. Fired right up as always. Just a little bit of shake at idle. RPM moves up and down a couple hundred RPM once warmed up. I'm sure it'll be different in the water. Below are couple videos to show the little bit of shake I'm talking about. I won't be able to get it out on the water until next Friday now.

This video is before last water test when I first noticed the miss on acceleration getting on plane. Seems to idle OK? What do you guys think?

https://www.youtube.com/watch?v=okhX8NTgTZ8


This video is from yesterday with the cowling removed. Running about the same today with the plugs regapped to .035.

https://www.youtube.com/watch?v=8F623yr-FLQ

It seems to be idling okay in the vidoes, but I'd rather see the videos with it idling on the water. A poorly running engine can idle and rev while on the muffs no problem. When you put the backpressure of water on the exhaust is when it runs in it's true form.

KJ

I never did update the verdict on this. I went out and got a can of OMC engine tuner and ran the whole can through the shrader valve on the primer solenoid. I also put the "old plugs" back in gapped at .030. Took it out and the problem was resolved. In order to determine if it was plugs or engine tuner that fixed the problem I put the new plugs back in gapped at .035 again and the problem re-appeared. So, I either go a bad batch or 1 bad plug, or my engine is really sensitive to the plug gap. And again, I carried the old plugs with me and changed them out on the water and again the problem was resolved.

My next check would be to put the new plugs back in gapped at .030 and see if I can run them. It's a bummer because the old plugs look pretty bad, but the engine runs best with them in there. I put an ohm meter on all the new ones and they appear to be OK.

Maybe I should try some NGK's that crossover the the Champion number?

Sounds like there might be a weak coil.----A check of peak coil output can be done.-------Will spark jump a gap of 7/16" on all leads , yes or no ?

Hey. Sorry for the late reply. Been busy with all kinds of stuff at work and home.

I never did put a spark gap tester on there. I can get one and try it. It's funny, one of my first thoughts was a weak coil after I brought the plug gap back down.

I had another issue last weekend (a new one). Engine was running good all day. I'm getting it ready for scalloping season here in June, so I have been out testing it to be sure it's not going to leave us stranded. I ran it for about 20 minutes heading into 2.5 chop in 18kt winds around 4800 RPM. Then I turned around and headed back the other way for about 30 minutes running it around 4400 RPM. Everything was fine, not one issue and was running great.... Until, I pulled off out of the intercoastal and up to an island in the shallows. I was sitting there at idle out of gear with the engine tilted about half way up for about 4 minutes putting gear away and getting ready to head to the boat ramp. All of the sudden, the engine shut off on its own like someone turned the key off? I tried to restart with no luck. Tried to restart with enrichment with no luck. The engine seemed to be turning over faster than normal? It just sounded different, don't know how to describe it. So, I dropped anchor, called the wife and explained what was going on before I called Sea Tow. I went back and removed the cowling and it smelled strong of gas. No visible leaks of any kind anywhere? So, I put the cowling back on went to the helm and set the throttle to WOT to see if it was flooded and maybe get lucky and have it start... It started, albeit running a little rough. I had to run it at over 2000 RPM to keep it from cutting off. I pulled anchor, started it again and managed to get it in gear and gun it. Once running over 2000 RPMs everything was normal again. I ran all the way back to the ramp around 4400 RPMs, nice and smooth, no issues. I also did quite a bit of idling getting back on the trailer at the ramp with no issuses. Also fired right up so I could flush it on the hose with no issues at all? Any ideas??? Was this just a fluke or something sinister about to happen. At this point, I don't know that I can trust it anymore.