All good advice above. I'd like to add one as well. Check the accuracy of your tach. You can get a hand held tach/dwell meter for next to nothing these days and verify that your dashboard tach is correct.
John
| www.iFourWinns.com https://www.smwebhead.com/phpBB3/ |
|
| 268 vista only 3800rpm wot? why not 4600rpm as specs? https://www.smwebhead.com/phpBB3/viewtopic.php?f=2&t=8657 |
Page 1 of 1 |
| Author: | fourwinnskiwi [ Sat Dec 03, 2011 1:17 am ] |
| Post subject: | 268 vista only 3800rpm wot? why not 4600rpm as specs? |
I have a 2001 268 vista with the 5.7 gxi and dup prop,the specs say it should hit 4600 rpm at wide open throttle,but for some reason she wont rev over 3800rpm ,ive tried in perfect conditions and with only 2 people on board,checked the props to be certain they are correct(which they are),the only thing I can think of is maybe throttle cable itself,I have noticed that when pushing the lever forward that it seems to move a bit before the engine revs increase,also when around 80% open there is no differance when pushing open the remaining 20%,could it just be adjustment? any thoughts on what could be causing this? I have fresh fuel and have had it tuned ,but still makes no differance,any help would be great ,thanks in advance ,Mike |
|
| Author: | Graham R [ Sat Dec 03, 2011 5:45 am ] |
| Post subject: | Re: 268 vista only 3800rpm wot? why not 4600rpm as specs? |
Mike, If it's a GXi, I believe the maximum revs should be between 4,800 and 5,200 rpm. It's normal for there to be the initial shifter position change where the revs don't rise. You can check the throttle is opening fully by removing the flame arrestor and having a look ( engine not running, in case it backfires !) . First thing I'd check is whether the flame arrestor needs cleaning. |
|
| Author: | efdog [ Sat Dec 03, 2011 8:32 am ] |
| Post subject: | Re: 268 vista only 3800rpm wot? why not 4600rpm as specs? |
I had this exact sounding problem when I bought my 248 last spring. It lasted about 2 hours at 3800 - 4000 RPM before a loud bang, then an engine surge and knock thereafter. Engine blown by the 4 and 6 cylinders and bored right through the head and block. All due to corroded ruined manifolds. Over $7000 in a repower that could have been under $1000 for just manifolds and risers. Have you ever hit 4800+ RPM's? Although there are several reasons you could have low RPM's, some more common reasons are props which you've ruled out. Hull growth build up. Fuel issues. You should really have a compression test done ASAP...and go from there. Hopefully in your case it's something minor, but please find out before doing irreversible damage! 3800 RPMS in not normal. Good luck and let us know what you find out. |
|
| Author: | BarryBoats [ Sat Dec 03, 2011 10:17 am ] |
| Post subject: | Re: 268 vista only 3800rpm wot? why not 4600rpm as specs? |
Also, I see that you are in salt water. Check for barnacle growth in the thru the hub exhaust. I had an experience where growth restricted the flow of exhaust and limited my RPM's severely. |
|
| Author: | Cap'n Morgan [ Sat Dec 03, 2011 2:08 pm ] |
| Post subject: | Re: 268 vista only 3800rpm wot? why not 4600rpm as specs? |
His boat was also a salty boat purchased in Punta Gorda Floida and shipped to New Zealand, so maybe some lingering manifold/riser issues from it's previous life. I agree 100% on the compression check also. |
|
| Author: | Winter Sux [ Sat Dec 03, 2011 7:34 pm ] |
| Post subject: | Re: 268 vista only 3800rpm wot? why not 4600rpm as specs? |
All good advice above. I'd like to add one as well. Check the accuracy of your tach. You can get a hand held tach/dwell meter for next to nothing these days and verify that your dashboard tach is correct. John
|
|
| Author: | fourwinnskiwi [ Sun Dec 04, 2011 1:33 am ] |
| Post subject: | Re: 268 vista only 3800rpm wot? why not 4600rpm as specs? |
Thanks for the suggestions everyone,I have only recently re-done the bottom paint,so no growth underneath at all,so cant be that,props are also good,manifolds and risers are almost brand new,had the gimball bearing universals replaced andbellows all replaced 2 weeks ago,the engine has only done 250 hours(20 hours by me)I had the motor tuned ,fresh fuel and filters as well.I guess the next step for me is to check the compressions and also take a look at the flame arrestor that was also mentioned as a posibilty.I think it would be unusual for the engine to have low compression on such low hours (wouldnt it?) any other suggestions I can check through while Im at it? thanks guys your help is really appreciated.I took her out today again for another run ,didnt push her to open throttle,just cruising around and dredging for scallops,but she starts well and runs well ,motor sounds very sweet,no smoke or anything that would suggest any mechanical issues of a serious nature,keep the ideas coming guys! thanks ,Mike |
|
| Author: | fourwinnskiwi [ Mon Dec 05, 2011 3:31 am ] |
| Post subject: | Re: 268 vista only 3800rpm wot? why not 4600rpm as specs? |
flame arrester cleaned out ,not bad just a little dirty,still no differance ,played around with trim tabs and outdrive trim,still no better ,the best I could get was 4100rpm,looks like a compression test is next on the list! uh oh! |
|
| Author: | efdog [ Mon Dec 05, 2011 12:18 pm ] |
| Post subject: | Re: 268 vista only 3800rpm wot? why not 4600rpm as specs? |
fourwinnskiwi wrote: I think it would be unusual for the engine to have low compression on such low hours (wouldnt it?) For a saltwater setup, the engine hours mean a lot less than engine maintenance. Another thought...If an engine is running on 6 of 8 cylinders, it may seem to sound great for a while. Hopefully this is not the case for you, and it's something simple. |
|
| Author: | fourwinnskiwi [ Wed Dec 07, 2011 4:06 am ] |
| Post subject: | Re: 268 vista only 3800rpm wot? why not 4600rpm as specs? |
Thanks ,I replaced the thermostat today as the engine wasnt reaching correct operating temp,With new thermostat in place(the old one was in 3 parts!) I took the boat out again and this time once she warmed up I opened up the throttle and managed to reach 4600 rpm,which is an improvement ,I also spoke with my marine mechanic who tells me that somewhere around the distributor is a plug which must be disconnected and connected to a wire with an alligator clip and earthed,then the timing can be set correctly ,I think he mentioned something about the electronic advance needing to be disabled.I also read up my manual and it says the timing should be set a 8 degress before tdc,does this sound correct? any help with this will be greatly appreciated ,my mechanic seems to think it may be a matter of the timing in need of checking.The engine runs perfectly ,smooth ,no smoke ,rattles ,back firing or anything at all to suggest its a serious engine problem and she is running on all 8 cylinders,The only thing she fails to do is reach max revs,thanks again guys |
|
| Page 1 of 1 | All times are UTC - 6 hours [ DST ] |
| Powered by phpBB® Forum Software © phpBB Group http://www.phpbb.com/ |
|