Carver 356 RPM issues

[km1125]

The stbd tach may be reading high and could be corrected via the method Viper suggests. That also makes sense since the sync gauge stayed centered.

Then, if both engines were at ~3200, it makes sense that you were around 20(+) knots. But then what doesn't make sense is if that was full throttle. I would expect way over 3200... perhaps 4200-4400. Have you ever had the boat at full throttle before and has it always topped out at ~20+ kts? Is the bottom clean?

[cpoint]

Thanks viper, I will try your suggestion. Bud hope it will be simple as that. The more I am thinking about it, hope it is tach gauge. I am still looking for a direct replacement for the tach gauges. Have not found one yet.

[cpoint]

km, I may be off with exact numbers on my posting. But pretty sure engines sounded similar when one was around 3k+ and other 5k. I only kept it there for a minute. Port side is definitely an issue, so it won't go past 3200 rpm. I still find crap in fuel filter (not water) some brown particles. But I am thinking the inline fuel filter may be filled also. Have not had time to look to find where it is yet, and hoping it is an easy change, otherwise mechanic cost is always several hundred regardless what you need done. The bottom was cleaned in last 2 weeks while boat was lifted to replace a sea cock and replace zincs. There was good deal of growth, so they had to scrape for a while and at a cost And while I am happy port side is now fuel issue and not a mechanical issue, all of a sudden in last 2 weeks the starboard side high RPM issue came up. But other then high RPM, I do not have any bad effects on starboard side, like unstable tach movements, etc. Starboard side fuel tank is pretty clean I believe. Had no issues with fuel there. I will tweek back of tach gauge this weekend as suggested by viper and bud. If it is not resolved, I will take out of marina and run each engine seperately to see if I can determine anything, and maybe I should head out to a mechanic school

[Viper]

I mentioned this before with respect to suspected fuel delivery issues and isolating each faulty engine from the boat's fuel delivery system: have you tried running the engines off of portable fuel tanks/jerry cans? Disconnect the fuel lines where they hook up to the engine (likely the primary filter), and plug them properly/securely. Hook up a fuel line that's long enough to take it out the side window where you'll hook it up to a portable tank that you'll secure to a stanchion or whatever is available in that area, don't put the tank inside the boat. Run the engines as normal and try to duplicate the problem. If it still happens, it's not your tanks or the fuel lines from them but something at your engines that is causing the problem. If it doesn't happen, then you've narrowed the fault to your fuel tanks, pick-ups, fuel lines, etc., everything before the engines.

I do this quite often when necessary and find it very helpful. Remember to ventilate and be mindful that you're dealing with fuel and all the dangers associated with it so be careful. After you remove fuel lines, run your blowers and wait for all the fumes to dissipate before you start your engines. I always keep the blowers running during this test.

[cpoint]

Thanks for suggestion viper. Don't have external tank. But was thinking running off the aux tank.

[Viper]

Have you been using your aux tank? If not, you're likely not going to get a trustworthy result. I'm sure you've read about aux tank issues here. The idea behind running off a portable tank is that it's a trustworthy setup that's isolated from the boat, that's the idea. It's a separate tank, new fuel line, and new fuel that doesn't have any garbage in it, or issues with the pickup or an anti-siphon valve. Don't spend another cent on replacing engine parts or cleaning your fuel tanks until you isolate whether the problem is with the engine or your boat's fuel or it's delivery system. This test will give you a clear answer so you know where to focus your efforts.

[km1125]

I agree with Viper's suggestion on the tank. When I had some "questionable" fuel several years ago, I bought a 6 gallon portable outboard tank and plumbed it into the port/starboard tank switch, replacing my port tank input. That would allow me to switch back and forth. I still have that tank and have used it for other things (including an outboard) but I'm sure I could throw it up on craigslist and recoup at least half of what I bought it for.


the long-story detail, if you're interested:
In my case, I had 4 year old fuel in both port and stbd main tanks, so I was unsure if it was good enough to use. I ran on the temp tank to get the boat to the slip, and then was going to resolve the tank. I then used a spare fuel pump and pumped several gallons out of the main port tank into a different portable tank to take home and analyze. I did a 'clarity' test, and vapor-pressure test (shake test) and the smell test - all was good, then I used it in some other engines and all seemed good. Then I went back to the boat and ran the engine for a while on the temp tank and then switched to the starboard main tank and did not notice any issues. However, when I did this I realized that when I was switching the fuel I was facing the aft of the boat and had confused my "left" with the "left" or "port" of the boat and had been switching the fuel opposite of what I thought. So I actually had been running on the main (starboard) tank most of the time while I thought I was on the temp tank!! Oh, well, I guess the gas was good afterall!!

[cpoint]

Thanks all. The aux tank was emptied last season, so it would be fresh fuel I would be putting in there. One thing though the switch for fuel tank selection is only aux/port for port side and aux/starboard for starboard side. Why would they not have put all 3 tanks as an input choice to either engine.... Also I am pretty confident of the following. AUX is clean, because I had it flushed and emptied last season. Starboard side have not seen any issues and fuel is fresh and filter had not contamination that replaced recently. Port side I am in the process of checking again, as there was definitely crap in it. Which caused a lot of chaos lats year.

[Samuel]

So what happen did you fix it ?

[mjk1040]

Aux. tank will feed both engines when selector is in that position. Sea Foam will get crap in tanks moving thru the system so you may want to change your fuel filters again! And I was told to trust the engine sync and not the tachs. Just my 2 cents.