Repairs & Maintenance

Subject
Topic: rpms to high / Prop change ???
mgl2748
BoatUS Member
BoatUS Member
Joined: 28 July 2017
Location: East Moline
Posts: 3
Posted: 28 July 2017 at 10:33pm | IP Logged
Hello I have a 1981 century 4000 21' cuddy. my rpms. are excessive about 5500 wot. my prop is 14"x 19 pitch engine is 260 mercruiser 5.7 v8.top speed is about 35mph. with 2 people. but comes on plane great. unless there are more people on board..My question is what would be the best prop to help with better all around performance?.. also my tach, may need replaced. cause the engine does not sound like its running that fast. any help would be appreciated ..Thanks
Edited by mgl2748 on 28 July 2017 at 10:34pm
RGrew176
BoatUS Member
BoatUS Member
Joined: 09 March 2002
Location: Southgate, Mi. 48195
Posts: 1467
Posted: 28 July 2017 at 11:34pm | IP Logged
Check the setting knob on the back side of your tach. It could be on the wrong setting. When I bought my last new boat the tach was reading wrong from the get go. I pulled the instrument panel off and the tach was set on the outboard setting. It needed to be on the V-8 setting. I changed the setting and from then on the tach's read accurately.

There should be a slotted knob on the back that you can change the setting with a screwdriver.

Good luck, hope it's as simple as that.
Rick Grew

1981 Carver 3007 Aft Cabin



2004 Past Commodore
West River Yacht & Cruising Club

www.wrycc.com
mgl2748
BoatUS Member
BoatUS Member
Joined: 28 July 2017
Location: East Moline
Posts: 3
Posted: 30 July 2017 at 9:19pm | IP Logged
I tried that first, tach read too low..thats why I think i have the wrong prop for my boat..
mgl2748
BoatUS Member
BoatUS Member
Joined: 28 July 2017
Location: East Moline
Posts: 3
Posted: 04 August 2017 at 12:55pm | IP Logged
Well I feel stupid..lol. A it turns out ,I followed some poor advise. My tach was set on position 4. where I was told it needed to be,for a four pole alternator.I was in the process of removing my Tach. when i noticed that #3 position said V8. I rest my Tach to #3 and BINGO! Tach dropped a thousand RPMS. took boat for a ride and Tach was still reading high at W.O.T. but closer to where it should be. I beached the boat and changed prop from 19 pitch to 21 pitch.She is now almost spot on.. I'm really happy. her rpms are still a little high so I am gonna try a 23 pitch next..At least now i am not worried that my engine is gonna explode due to over rev,. thank for any and all advice.
Edited by mgl2748 on 04 August 2017 at 12:56pm
Audrey II
BoatUS Member
BoatUS Member
Joined: 27 December 2009
Location: Haverstraw, NY
Posts: 2618
Posted: 04 August 2017 at 10:23pm | IP Logged
No reason to feel stupid this is how we learn! This is the reason for forums like this and this is why it would be a shame for them to turn off this forum even if the use is down I think it should simply be promoted more and encourage more boaters to come share and learn!!



96' 440 Trojan express

Dave
RGrew176
BoatUS Member
BoatUS Member
Joined: 09 March 2002
Location: Southgate, Mi. 48195
Posts: 1467
Posted: 04 August 2017 at 11:05pm | IP Logged
So, your tach was on the wrong setting. That and a propeller change have you close to spec. Glad you were able to figure it out.

Hope all your future boating problems are as relatively simple to figure out.
Rick Grew

1981 Carver 3007 Aft Cabin



2004 Past Commodore
West River Yacht & Cruising Club

www.wrycc.com

If you wish to post a reply to this topic you must first login
If you are not already registered you must first register

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot delete your posts in this forum
You cannot edit your posts in this forum
You cannot create polls in this forum
You cannot vote in polls in this forum
Forum Jump 


This page was generated in 0.1719 seconds.