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3.0 hard to start and running poorly after getting wet

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Joined: 15 Mar 2009
Posts: 2
Location: New Zealand

PostPosted: Sun Mar 15, 2009 1:45 pm    Post subject: 3.0 hard to start and running poorly after getting wet Reply with quote

OK. This will be a long post but I wanted to give as much information as possible Smile

I have a 1996 Four Winns Horizon with a 3.0 Volvo Penta driving through a Cobra SX drive. Four weeks ago the main water hose from the water pump to the thermostat housing split. By the time I noticed, the bilge was full of water (maybe 4 inches or so deep) but the engine didn’t display signs of overheating and was idling smoothly. This was all in fresh water. The boat has never been near salt. I replaced the hose and was back on the water within a couple of hours. The boat continued to start, idle and run at wakeboarding speeds (3200rpm) without any evidence that anything was different. However, when cruising at higher revs (4000+) the boat would develop a slight miss, lose power and eventually die. It was then harder to start than normal but would start and run fine again without any issue. This happened several times. Prior to the hose splitting, the boat had run perfectly without any issues.

I put it into the mechanic - a top commercial Volvo Penta shop and not a back yard outfit so I’m comfortable with their expertise. They checked the compressions and did a leak down test. The compressions were OK but the leak down test showed problems with number 3. There was no evidence of water in the oil. As a result the head gasket was replaced and at the same time the manifold and riser were checked and found to be OK and those gaskets replaced also. The head was warp tested and was OK so the valves were lapped and it was put back together, along with new spark plugs. A fresh leak down test showed good results. On the first run it was apparently running very rough so the carb was cleaned out. It then ran smoothly but on-water testing showed that it still had the missing / stopping problem at the higher revs. The fuel filter was checked and the fuel pump tested for pressure and flow and everything was pronounced fine. They also tried a different tank of fuel to no avail. One of the relays was also replaced as apparently these had been known to cause the type of symptoms displayed. This weekend, knowing that it had issues, I picked the boat up to give it a good run and see if, knowing the boat personally, I could identify anything further.

The first problem was that it wouldn’t fire at all. It would turn over freely but there was no hint of it firing. It has always started very easily, even from cold so this was strange.

I gave it a rest for 30 minutes or so as I was called away. When I tried again, I wondered if it was somehow related to the angle of the stern leg so lowered the leg fully and it fired right up. This could be a coincidence but it is worth mentioning.

It idled well so I went out for a run. Everything seemed normal, like it was before the hose splitting incident. However, it wasn’t long before the high rev miss showed up and the boat died. It wouldn’t restart and I needed a tow back to the jetty.

I finally managed to get it started there but only after a lot of perseverance, trying different throttle settings and so on. Using different tilt settings didn’t make any difference. It seemed that when it fired it was more luck than anything.

It would not idle under 2000rpm and was running very rough but was running consistently - i.e. not as if one cylinder was coming and going for example. My guess is that this is what the mechanic was describing as running rough which caused him to suspect a dirty carb. I now wonder if this was a dirty carb after all. A couple of times I tried to put it in reverse to back out from the jetty but in going from fast idle to reverse it just died through lack of revs.

Temperature and oil pressure were normal – the same as what they have been for the past 4 years, however the trim gauge was not working and had always been OK. When we first got the boat there was no response to the key and an earth bypass was run from (what I think is) the tilt limit relay / switch. Anyway, removing this stops any response from the ignition key. Refitting it means the starter engages as normal. Again, coincidence or .....?

I took the distributor cap off and cleaned up the contacts. I don’t think this made any tangible difference. There was no moisture inside the cap.

Over time just running at the jetty it slowly got better. It would idle at around 750rpm but there was a noticeable hesitation when the throttle was blipped before the revs picked up. Thinking this felt like a fuel/air mixture I experimented with different mixture screw settings but nothing really changed. Applying throttle slowly would mask the problem and the motor revs increased smoothly.

I then spent about two hours driving for wakeboarders and towing biscuits. For each, the revs were around or under 3200rpm. The boat never missed a beat when running. The motor was regularly turned off so people could climb back on board. About once in every 5 starts the boat would just refuse to fire at all. Sometimes I could get it to start by leaving it with no throttle and at other times by pumping the throttle. There seemed to be no logic to it. Once running, it was fine again. However, whenever I ran at higher revs, it wouldn’t take long before the missing problem reappeared. If I was quick and reduced revs to about 2000 I was able to avoid it stopping.

My logic says that the current problems must be related to the split water hose as everything was perfect before this. Mind you, this is only logic but the boat gets used regularly for watersports and had never caused any frustrations. I notice that the distributor is very close and slightly below the hose that split. Could this have been damaged with all the water pumping out that hose? What about any other electrical components, particularly those lower down that may have got wet when the bilge filled? Is the non working trim gauge pointing to a problem that may be causing the running issues?

I have the boat back home at the moment and thought I would consult the experts on this forum before putting it back into the shop. Any help would be much appreciated. Any questions are welcomed. Thanks in advance for your help.
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Joined: 15 Mar 2009
Posts: 2
Location: New Zealand

PostPosted: Tue Mar 17, 2009 3:36 pm    Post subject: Reply with quote

Hi, looking forward to some replies, help and direction from the experts out there Smile
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