Engine tops out at 3000 rpm
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=51361
Printed Date: November-22-2024 at 2:59am
Topic: Engine tops out at 3000 rpm
Posted By: garykocis
Subject: Engine tops out at 3000 rpm
Date Posted: September-06-2023 at 5:07pm
I own a 1979 Mustang 17 with ford 302 engine. Sadly, just got it out on the water for the first time this year.  Initially, it was running fine and I took a couple runs. Had a short rest and was skiing again and engine topped out at 3000 rpm. Simple would not run faster than this, even at full throttle. Tried again with no skier and observed the same. Also noticed some hesitation/roughness when accelerating.
First idea is to run some Sea Foam Motor Treatment through the engine to see if that helps. I did have stabilizer in the gas over the winter. I've also seen some postings that mention fuel system, carburetor, accelerator pump, anti-siphon valve, etc. Regards, Gary |
Replies:
Posted By: MrMcD
Date Posted: September-06-2023 at 8:02pm
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I think the first check in my book would be the distributor advance. Make sure it is working, free and smoothly. With no advance an engine will not run even close to full performance. There are several threads on this forum that discuss this. With a timing light hooked up you should see your timing at idle somewhere around 10*, as you increase RPM you should watch the timing mark advance, it should max around 34* advance somewhere below 4,000 RPM. It needs to advance the same each and every time and be very smooth. Any rust in there keeps this from working properly. A very common issue in boats. While in there check the springs to be sure both are in good shape. If you have a timing light this is a 10 minute check start to finish and if nothing else it lets you know what to rule out. ------------- |
Posted By: garykocis
Date Posted: September-06-2023 at 8:21pm
| Thanks for the suggestion, I do have a timing light. Will check this (maybe tomorrow?). |
Posted By: garykocis
Date Posted: September-07-2023 at 12:17pm
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So I ran the engine on dry land to check the distributor/timing advance. Per usual for me, the engine seemed to run fine today. Sounded better/smoother, could rev it up to 3600 RPM. Either this means the issue is intermittent or that it behaves different with no load on the engine. I took videos of the data from the timing light, and I need to look at this myself. The other challenge is that between my eyes, and the markings I could not easily read how the timing was changing at different RPMs. Hopefully my videos will provide that information. More to come...
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Posted By: garykocis
Date Posted: September-07-2023 at 3:36pm
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Results from my morning effort with timing light: Idle: 800 RPM >>> - 6 degrees 1500-2000 RPM >>> 18 degrees 2400 RPM >>> 20 degrees 2800 RPM >>> 25 degrees So, I do observe that the timing is advancing (a net of 31 degrees from idle to 2800 RPM). I was not able to upload videos, but can try again if that would be helpful. First picture below shows timing light mark at 800 RPM (idle). Second picture shows the full scale showing that the white markings ("-") are at the -10 degree position. Yellow mark is 10 degrees, and white "0" is marking 0 degrees. .  Some additional background: I had the engine rebuilt about 5 years back. After that, I could not get the engine to start if I set timing to be at 10 degrees. For instance, I marked the distributor position before having the engine rebuilt and used that to reset the position. Really needed to deviate to get engine to start/run, which is probably why I am at negative 6 degrees. Not sure if this has any bearing, but wanted to mention it.
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Posted By: KENO
Date Posted: September-07-2023 at 8:01pm
I think it's safe to say that timing advance isn't your issue and your damper has been that way for years so it's not your issue either.  You'll have to run it under load for a good check to see if it cured itself.
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Posted By: garykocis
Date Posted: September-10-2023 at 8:23am
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Just wanted to say thanks to MrMcD and Keno for your responses! My son has the boat out this weekend, so I will learn how it was running on the water. Any chance that there could still be a timing advance issue that is intermittent? Gary
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Posted By: 63 Skier
Date Posted: September-10-2023 at 2:39pm
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Since when you were first out it was running fine, seems to me something happened that is limiting fuel or ignition between your good runs and shutting down and starting up again. When it wouldn't run over 3000 rpm, was it still running smoothly? Any roughness or popping sounds? I'd look at plug wires and plugs, disconnect and reconnect every one from both ends, same with coil wire, pull the plugs and observe if they look decent and gapped correctly. If you haven't looked at the anti-siphon valve that is definitely a source of problems (I'm assuming a '79 Mustang had one, not sure?). I guess let's see how it ran for your son and take it from there. ------------- '63 American Skier - '98 Sport Nautique |
Posted By: garykocis
Date Posted: September-10-2023 at 3:50pm
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So, in first outing the engine was running fine for say 30 minutes before I started to notice loss of power/speed. At that time, it was not running particularly smooth - would sound rough when accelerating hard from a standstill. The report from my son this weekend was that he thought is sounded rough at times, and mentioned excess smoke in exhaust. But, he said no problem running above 3000 RPM. I will need to get the boat on the water again. Was reading the other recent posting (351 W won't run up after restart). So I am also thinking about.... "new gaskets in both between the spacer and manifold and the spacer and carburetor" Appreciate the comment on spark plugs/wires. Gary
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Posted By: Gary S
Date Posted: September-10-2023 at 11:40pm
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Have you changed the points and condenser lately by any chance? My dad had a 302 PCM that started giving him trouble- fought it for a long time. Finally stumbled across the distributor getting corroded between it and the block and the housing not being grounded to the block. Ended up cleaning that and running a ground wire direct from the distributor to the block. Just throwing that out there since I know how frustrating it can be ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: KENO
Date Posted: September-11-2023 at 7:16am
| I'm thinking that if he looks under the cap, he'll find an electronic module under there, but that he should also look at the the rotor and the contacts in the cap too for corrosion, wear etc. |
Posted By: Gary S
Date Posted: September-11-2023 at 10:52am
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Do you have insider knowledge that he has electronic ignition in a 79? Pop bought his 87 new it had points ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1711&sort=&pagenum=1&yrstart=1966&yrend=1970" rel="nofollow - 69 Mustang HM SS 95 Nautique Super Sport |
Posted By: KENO
Date Posted: September-11-2023 at 12:01pm
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I asked Carnac, but I don't think he's really all that clairvoyant https://imgbb.com/" rel="nofollow">  I think he did a search and found this old thread http://www.correctcraftfan.com/forum/forum_posts.asp?TID=42809&KW=ignition&PID=550025&title=rebuilt-engine-ford-302#550025" rel="nofollow - old thread |
Posted By: MrMcD
Date Posted: September-11-2023 at 1:07pm
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Distributor timing appears to be working, as Ken suggested I would look at the cap and rotor for condition and corrosion. Next I would pull all 8 spark plugs, lay them out side by side, marked as to what cylinder they came out of and study them. You might see certain cylinders that are not burning clean. That could be cause by bad plug wires or the cap./rotor. If it has not shown up at that point and the Points/electronic ignition are good you are moving into mechanical issues. Heads, head gaskets. Start with he simple and make sure all the normal tune up stuff is good before anything else. You might even verify the fire order is correct from the distributor to the spark plugs. People work on things and they don’t always get put back correctly. ------------- |
Posted By: garykocis
Date Posted: September-11-2023 at 4:35pm
Posted By: garykocis
Date Posted: September-11-2023 at 4:38pm
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Keno is spot on! Had electronic ignition upgrade several years back. Will look at dist cap, rotor, but I don't think I will know how to recognize an issue (maybe corrosion, burn marks, wear, ...).
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Posted By: KENO
Date Posted: September-11-2023 at 5:59pm
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You'll recognize an issue by looking for what you describe. Here's a picture of a couple of pretty ugly terminals with all of what you described. The rotor tip will get equally ugly too. https://ibb.co/bQwn73J" rel="nofollow">  There will always be a little ugliness and wear because of the spark jumping the gap, but when the white corrosion builds up too much you'll have problems like misfiring, weak spark etc.
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Posted By: garykocis
Date Posted: September-12-2023 at 10:34am
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Checked the distributor cap; very clean. Contacts are shiny, with just a small char mark in the upper right corner (all 8). Pretty uniform. Rotor also looks fine to me. I had replaced these, and the spark plug wires when the engine was re-built. Since I pulled the plugs, I will replace them just to be sure. Spark plug wires all appeared to be well connected even though distributor cap is quite crowded. my firing order is a bit odd. My engine owner's manual say RH rotation should be: 1-8-7-3-6-2-4-5 my setup is as follows (and I had hand-written notes in my manual with this order): 1-8-4-5-6-2-7-3 thus, I see swaps between: 4&7, 3&5
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Posted By: garykocis
Date Posted: September-12-2023 at 10:37am
| ok, just saw Keno's posting on firing order with early/late cam. so, this now makes sense (I think). |