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AZ86SKI 
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Joined: July-05-2022 Location: Phoenix, AZ Status: Offline Points: 115 |
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 Posted: July-15-2022 at 1:59pm |
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Well...I couldn't wait until weekend to check the timing as we discussed, so the neighbors got to listen to 3500 rpms this am (not too early though).
 At idle which is about 750 RPM the initial timing is set at 12 degrees BTDC. Idle under 750 RPMs seems like it wants to try and stall, so that's where I have kept it. At 2000 RPM the timing is about 22 degrees and at 3500 RPM the timing is in the mid 30's. It is hard to tell the exact number as it was bouncing around a bit, but my best estimate would be about 35 degrees. At 3000 RPM it made a few popping noises, not backfiring though, and then smoothed out. That engine has not been run at those RPMs in quite some time. Sounded great once it smoothed out though. I can only assume my mechanics notes regarding timing at 24 degrees at 3000 RPM were somehow inaccurate. However, these are the numbers I am seeing, which seems more in line with what they should be based on the recommendations. Any thoughts?
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MrMcD
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Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3604 |
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Posted: July-14-2022 at 9:36pm |
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Dang, that would have been an easy fix. Hope the real fix comes along soon.
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AZ86SKI
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Posted: July-14-2022 at 9:02pm |
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Tommrupp,
Thank you for the tip. I will definitely get that downloaded. I am hoping that when the top end issue is resolved on this boat that it will take off like a rocket and break the one working speedometer needle. I'm kidding (half kidding).
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AZ86SKI
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Joined: July-05-2022 Location: Phoenix, AZ Status: Offline Points: 115 |
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Posted: July-14-2022 at 8:55pm |
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Mark,
I am optimistic that the total timing issue will be confirmed (confirmed as a problem). I will definitely get those results posted soon. I followed a previous post awhile back that described advancing the throttle forward to the detent and then attaching the other end of the throttle cable to the carburetor at that point. The explanation I read (to include the neutral position for the transmission) was much better than mine, but it seemed to get me extremely close to what I think feels right (or close to right) on the linkage. Thank you for the recommendation on checking the primary butterflies at WOT. This is something I had not done. I just checked and the primary butterflies are both fully open at WOT. Anything we can check off the list is a win. Thanks. |
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KENO
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Joined: June-06-2004 Location: United States Status: Online Points: 10715 |
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Posted: July-14-2022 at 8:22pm |
If you set the linkage correctly, hopefully you checked for full opening of the primary butterflies, but if you didn't then MrMcD's suggestion would be the next thing to check. It would be a nice easy fix
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MrMcD
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Posted: July-14-2022 at 4:06pm |
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I had issues with my first Nautique, a 1978 351W boat. The 4 barrel would not open for most of a summer before I got it fixed. We were able to ski just fine, pulled up heavy skiers no problem and I think it would still run up to at least 4,000 RPM no problem. It was just not as fast with only the 2bbl working.
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Tomrupp
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Joined: October-14-2021 Location: MI Status: Offline Points: 73 |
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Posted: July-14-2022 at 3:54pm |
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As for #5, download a GPS speedometer to your smart phone. They are accurate and free of charge. I do encourage you to get the original 2 speedos working, but smooth running 351 would be my 1st priority.
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Tom
94 Ski Nautique Open Bow 351 with Carb 95 Double Decker Aqua Patio with 50hp Honda (3 carbs). |
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MrMcD
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Posted: July-14-2022 at 3:38pm |
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Just to help on the timing as Ken recommended, your distributor can give you 20 to 24* advance. So your initial setting of 12* would give you somewhere between 32 and 36 TOTAL timing which is the number you want to know for good performance.
It does sound like your carb still has some issues but the first thing I would verify is your throttle cable connection. Make sure when you open the throttle from the driver seat it actually does open the throttle at the carburetor. You would need to remove the spark arrestor, Engine turned off, open the throttle full and look down the carb to see how far the butterfly's are open. You will probably need to open the choke first by hand to see what the butterfly's below the choke are doing. This will verify your Primary, (front 2 barrels of your 4 bbl carb) are doing. If they are not straight up and down with your throttle wide open it can be adjusted to fix it. This is a simple 5 minute check to do before getting into complicated stuff. Nice work so far. Mark
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AZ86SKI
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Posted: July-14-2022 at 3:27pm |
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I will double check the initial and total timing at 3500 rpms this weekend (if not sooner) and post the results. Thanks again! |
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KENO
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Posted: July-14-2022 at 2:56pm |
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I think you're doing your homework really well
There should be about 30 to 34 degrees advance at 3500 RPM. You should have 20 to 24 degrees of mechanical advance on top of your initial idle setting . DUI says 24 degrees of mechanical advance from the flyweights and springs that are installed. People seem to see between 20 and 24, but that's still a lot more than what looks like 14 degrees of mechanical advance that you have now. I'd check that for sure. Check the initial and the total. The prop is right for the boat and the speed vs RPM correlation is right.
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AZ86SKI
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Posted: July-14-2022 at 2:20pm |
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KENO,
Thank you for reply. I really appreciate it. 1. On the trailer in neutral, the timing at 3000 rpms is at 24 degrees. This from my mechanics notes when the DUI conversion was done. I can check it again myself and get it up to 3500 rpms and check it there as well if that would help. I should also note that the distributor that I replaced was a motorcraft automotive distributor, so it must have had distributor issues in the past. 2. The prop markings are "7 85 FEDERAL NI-BRAL CUP 13RH13". 3. Your explanation of only getting to 2700 rpms not being enough to create the vacuum signal makes a lot of sense versus engine vacuum. I guess I should also mention that I replaced the secondary spring to one lighter in hopes for a solution but there was no change which again supports your point. 4. Regarding dirty passages in idle circuit. I know very little about the internal parts of the carburetor, so I have left that to the experts. I've had the carb rebuilt twice now by reputable shops, once when I first got the boat about a year and half ago to at least get it running and then again recently when the DUI conversion was done when the mechanic noticed excessive fuel delivery. I would hope it's clean by now, but I'm not ruling anything out with this boat at this point. 5. Only one of the speedometers is working at this point (I can't wait to be able to work on those things whenever I get past these issues). However, it appears to track the RPMs fairly close to 1:1. 2700 rpms is showing close to 27 mph. Hopefully this helps, please let me know what you think. Thanks |
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KENO
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Posted: July-13-2022 at 9:13pm |
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A couple of things come to mind
Your timing is at 12 degrees BTDC at idle speed, what is it a 3500 rpm revving it in neutral. It should get there easily in neutral with no load on the engine and the timing should end up at somewhere between 32 and 36 degrees. Your vacuum reading of a steady 15 to 16 sounds OK. What do you have for a prop on the boat? it would take a way oversized prop to keep RPMs that low but it's worth asking the question If you're only getting to 2700 RPMs your secondaries won't open due to not enough air flow down the venturis.to create the vacuum signal that opens them. (it's not engine vacuum) If everything was good, and the secondaries weren't opening you'd only be down a few hundred RPM from a normal of about 44 to 4500 ish and be down a few MPH also. 3 to 3.5 turns out on the idle mixture screws would be telling me you have some restricted/dirty passages in the idle circuit. Good job getting a picture posted in your first post. Ok, so that was more than a couple of things And in true Colunbo fashion......................just one more thing, when you're at 2700 RPM, how fast is the boat going ?
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AZ86SKI
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Joined: July-05-2022 Location: Phoenix, AZ Status: Offline Points: 115 |
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Posted: July-13-2022 at 6:09pm |
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Hello all,
I have been following this site for over a year and this is my first post. Before I begin, I would just like to say there is no way I would be even close to how far along I have come to bringing this boat back to life without all of the great technical advice I have read on this site. Not to mention the humor and inspiration of other member's much greater projects to keep me motivated, so thanks again. So, this where I am at. I have a 1986 Ski Nautique with a 351W Commander package. I had been storing the boat for a family friend for a number of years, but it sat due to mechanical issues but reportedly ran great at one time. They ended up leaving the state and I became the new owner and I have been working on it ever since. I feel I am very close experiencing the boats full performance, but I am stumped with some final acceleration issues and could use some advice. Acceleration problem #1: On the water under load, when I give it throttle from idle it stumbles and dies. I does much better in reverse as there is not as much load as I have read. I can increase the idle and throttle my way through/around it but the high idle makes it tricky around the docks and is not a long-term solution and can't be great for the transmission. There was a previous post "Stalling in forward" that was very similar, but there was no solution posted. I have also followed the posted advice on setting the throttle cable linkage correctly as well. Acceleration problem #2: On the water under load at about 2700 rpm, additional throttle does not increase RPM/speed. Which feels to me as if the secondaries are not opening. However, that is based only on what I suspect on what I have read. I have not had the opportunity to physically observe that this is the case as the GF has not yet agreed to help me check this on open water under load. Since she had to help me push this boat after it has died on the water once or twice already, I'm giving her a little room this one.  Seems to run great once past the stall attempt from idle and to the 2700 or so rpms. The following is based on what I have done, and some based on what my boat mechanic has advised. I will try to limit what was done in regard to acceleration issues. Compression test was good (can provided numbers if needed). Leak down test was good. Holley 4160 Carburetor was rebuilt by mechanic. Holley wedge plate was installed/all new gaskets by mechanic but not skidim gaskets as I have seen suggested. All new fuel filters and all new fuel. DUI conversion done by mechanic. New wires, new plugs (no fouling), wiring order triple checked. Timing set to 12 degrees BTDC Manifold bolts tightened to spec. Electric choke adjusted and verified that it is fully open when warm. Vacuum leaks checked around base of carb and manifold. (3/4 can of carb cleaner and 1/2 bottle propane) -It doesn't mean it's not there, but I haven't found one. -Vacuum gauge from back of carburetor to the PCV (Not on a T but directly from the PCV hose) shows a steady 15-16 lbs. vacuum. It is my understanding it should be showing 19-22. Other possible indicators: At idle (no throttle at all) seems fine from when its first started and idling at the boat launch. When I come off throttle to idle after a run (at a whopping 2700 rpms ) the idle hangs high (1000 rpms or so). When the engine cools after sitting, the idle drops back down. Also, both cold and hot starts need a pump of the accelerator to start. Cold start needs three pumps and throttle left open 1/3. Hot starts need one pump. Finally, the idle mixture screws seem happiest at about 3-3.5 rotations out (based on my vacuum test). My thoughts are a vacuum leak, but I can't find one and I could also be completely wrong. I have attached a photo of the engine if anyone sees anything obvious that may be related or not that needs addressing (and to see if I could post a photo correctly). Any advice would be greatly appreciated. I hope I have described this somewhat clearly and look forward to being part of this great community.  |
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AZ86SKI wrote: