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BoatCrazy
RO# 30843
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Posted - Jul 29 2010 : 08:57:30
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My 97 120hp Force is only reaching 4500rpms. Should be 5500.
Motor starts right up and idles nicely..You can rev the motor pretty high in neutral, but once it goes in gear, she only reaches 4500..
Could the carbs need to be rebuilt? They were just cleaned...
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1990 Searay Sundancer 310 twin 5.7 mercs Alpha I's "Victim Of Fate"
1988 18' Anacapri Center Console, 1985 V4 Johnson 120hp with a V6 gear case -
1971 23' Glastron V234 - Yamaha 5.0 litre V8 260hp "Drifter II" |
Edited by - BoatCrazy on Jul 29 2010 10:29:28
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Homeport: Massapequa NY
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pdecat
RO# 842
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Posted - Jul 29 2010 : 10:21:30
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dirty prop or boat bottom???
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Bruce
legal disclaimer;
posts are amateur opinion only and should not be relied on as reasonable, safe, proper or in any way recommended.
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Edited by - pdecat on Jul 29 2010 10:21:56 |
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Homeport: Gulf Coast FL
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BoatCrazy
RO# 30843
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Posted - Jul 29 2010 : 10:29:04
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First time this motor has been in the water this season, and same for the boat..prop is brand new, and the bottom is freshly painted
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1990 Searay Sundancer 310 twin 5.7 mercs Alpha I's "Victim Of Fate"
1988 18' Anacapri Center Console, 1985 V4 Johnson 120hp with a V6 gear case -
1971 23' Glastron V234 - Yamaha 5.0 litre V8 260hp "Drifter II" |
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Homeport: Massapequa NY
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pdecat
RO# 842
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Posted - Jul 29 2010 : 12:57:48
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I doubt it is carbs. check fuel quality, filters, tank vents etc also check that throttle actually opens fully.
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Bruce
legal disclaimer;
posts are amateur opinion only and should not be relied on as reasonable, safe, proper or in any way recommended.
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Homeport: Gulf Coast FL
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BoatCrazy
RO# 30843
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Posted - Jul 29 2010 : 13:01:38
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Brand new fuel. Fuel tank was drained and cleaned. All new fuel filters, and water fuel separator. Throttle does open fully. It revs higher in neutral then it does in gear, which is why I think its the carbs..
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1990 Searay Sundancer 310 twin 5.7 mercs Alpha I's "Victim Of Fate"
1988 18' Anacapri Center Console, 1985 V4 Johnson 120hp with a V6 gear case -
1971 23' Glastron V234 - Yamaha 5.0 litre V8 260hp "Drifter II" |
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Homeport: Massapequa NY
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BillWilliams
RO# 2904
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Posted - Jul 29 2010 : 15:14:18
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You mentioned brand new prop. Is it the correct size? Too much pitch and you won't reach your max RPM.
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Bill W.
1989 Sea Ray 268 Sundancer - "Bare Necessity" |
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Homeport: Higginsport, OH
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BoatCrazy
RO# 30843
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Posted - Jul 29 2010 : 19:21:20
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yes its the correct size. Its definitely something within the motor.
First go around the boat wouldnt even get up on a plane. I went back to the dock pulled the carbs apart to see what was what. Then I stick a needle in the jets to make sure they werent clogged. I reved the motor a few more times at the dock and went back out for another run. boat got up on plane and sounded much better. Only thing is its missing 1000rpms...
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1990 Searay Sundancer 310 twin 5.7 mercs Alpha I's "Victim Of Fate"
1988 18' Anacapri Center Console, 1985 V4 Johnson 120hp with a V6 gear case -
1971 23' Glastron V234 - Yamaha 5.0 litre V8 260hp "Drifter II" |
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Homeport: Massapequa NY
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KinCal
RO# 15235
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 Posted - Jul 29 2010 : 20:29:26
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quote:
Originally posted by BoatCrazy
It revs higher in neutral then it does in gear, which is why I think its the carbs..
Higher RPM in neutral VS under load is normal.
When you say the prop is the correct size does that mean it is the exact same prop that it replaced? Even then the previous prop may have been reworked and had pitch taken out.
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| Kerry |
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BoatCrazy
RO# 30843
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Posted - Jul 30 2010 : 00:40:15
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Its the same prop dimensions that has been on this motor. The old prop had never been reworked or anything.
Once I pulled the carbs apart, at the dock, the motor got better, which is also why I think its a carb issue...
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1990 Searay Sundancer 310 twin 5.7 mercs Alpha I's "Victim Of Fate"
1988 18' Anacapri Center Console, 1985 V4 Johnson 120hp with a V6 gear case -
1971 23' Glastron V234 - Yamaha 5.0 litre V8 260hp "Drifter II" |
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Homeport: Massapequa NY
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Chief Alen
RO# 31229
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Posted - Jul 30 2010 : 08:07:40
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same motor we talked about ?
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| Be good, be happy for tomorrow is promised to no man. |
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Homeport: Manalapan, NJ
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BoatCrazy
RO# 30843
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Posted - Jul 30 2010 : 09:53:58
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Yes its the same 120 Force we talked about a few days ago. Ill tell ya though, the motor wants to go I hear it, but something is bogging the motor down.
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1990 Searay Sundancer 310 twin 5.7 mercs Alpha I's "Victim Of Fate"
1988 18' Anacapri Center Console, 1985 V4 Johnson 120hp with a V6 gear case -
1971 23' Glastron V234 - Yamaha 5.0 litre V8 260hp "Drifter II" |
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Homeport: Massapequa NY
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Chief Alen
RO# 31229
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Posted - Jul 30 2010 : 10:04:47
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You cleaned the fuel filter ? Small restriction there maybe.
What i did once was let someone else drive and i sprayed carb cleaner in the upper carb and it took off, we were hitting a glass ceiling also and i knew she wanted to take off.
Hows the t-stat ? Me i found a problem on a 175 the t-stat was frozen closed and the poppit valves were frozen half closed wouldn't let it get to wot.
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| Be good, be happy for tomorrow is promised to no man. |
Edited by - Chief Alen on Jul 30 2010 10:08:28 |
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Homeport: Manalapan, NJ
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BoatCrazy
RO# 30843
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Posted - Jul 30 2010 : 10:47:57
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Brand new fuel filter. Its just weird that once I messed with the carb the motor improved. The carbs look clean, but its what you cant see that could be the problem.
Thermostats I havent touched, motor runs cool, so I assumed all was good.
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1990 Searay Sundancer 310 twin 5.7 mercs Alpha I's "Victim Of Fate"
1988 18' Anacapri Center Console, 1985 V4 Johnson 120hp with a V6 gear case -
1971 23' Glastron V234 - Yamaha 5.0 litre V8 260hp "Drifter II" |
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Homeport: Massapequa NY
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pdecat
RO# 842
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Posted - Jul 30 2010 : 11:44:20
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some OBs have a screen filter at the fuel pump
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Bruce
legal disclaimer;
posts are amateur opinion only and should not be relied on as reasonable, safe, proper or in any way recommended.
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Homeport: Gulf Coast FL
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BoatCrazy
RO# 30843
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Posted - Jul 30 2010 : 12:40:01
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Yes, the screen is clear.
Im 99% sure its a carb issue. Once I tinkered with the carb it gained more RPMs. At first run it only turned 1800rpms, then I took the carb apart put it back together reved the motor pretty high, went back out and it turned 4500RPMs.. That leads me to believe its a jet that is slightly clogged, maybe the throttle linkage needs adjusting...?
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1990 Searay Sundancer 310 twin 5.7 mercs Alpha I's "Victim Of Fate"
1988 18' Anacapri Center Console, 1985 V4 Johnson 120hp with a V6 gear case -
1971 23' Glastron V234 - Yamaha 5.0 litre V8 260hp "Drifter II" |
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Homeport: Massapequa NY
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BoatCrazy
RO# 30843
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Posted - Aug 05 2010 : 21:27:57
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I just rebuilt the carbs on the motor, and took it for a sea trial. The motor has MUCH more power. Much quicker to respond with the throttle. Not that it would hesitate up acceleration, it was just sluggish.
Motor went from spinning 4500rpms to now 5000-5100rpms. I was told by my local force parts department, that the 120 Force should have a top end of 5250rpms.
I was under the impression all 2 stroke outboards should be at 5500rpms, or is that just OMC? Never owned an outboard other then OMC till now.
Now I just have to get a smaller prop to gain the extra 100rpms. I was wrong about it being the right sized prop for the boat. But the carb rebuild made a HUGE difference...
Is 5250rpms for this motor correct?
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1990 Searay Sundancer 310 twin 5.7 mercs Alpha I's "Victim Of Fate"
1988 18' Anacapri Center Console, 1985 V4 Johnson 120hp with a V6 gear case -
1971 23' Glastron V234 - Yamaha 5.0 litre V8 260hp "Drifter II" |
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Homeport: Massapequa NY
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Chief Alen
RO# 31229
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Posted - Aug 06 2010 : 16:39:01
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forget what year but normal compression would be 80 psi on some motors. Leads me to believe the low compression motor would be hard pressed to reach 5500 rpm.
Maybe your getting all you can get, with this one ? I would still look at the t-stat and popit valves. You might be surprised .
You think there was water in the bowls and you finally got it all, or another piece of dirt clogged a jet, don't take alot ?
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| Be good, be happy for tomorrow is promised to no man. |
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Homeport: Manalapan, NJ
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BoatCrazy
RO# 30843
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Posted - Aug 07 2010 : 06:45:44
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I have the manual for the motor and it says compression should be 150psi, im at 160. It also says that WOT should be 5250rpms.
I checked the thermostats and they are clean and in working condition. Looks as if they were replaced recently. I didnt know what was going on with the carbs so I rebuilt them and from that point on its been night and day difference.
I never run the boat at WOT anyways, so Im fine running the motor as is. I just dont know if Im going to do any damage to the motor running it the way it is.
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1990 Searay Sundancer 310 twin 5.7 mercs Alpha I's "Victim Of Fate"
1988 18' Anacapri Center Console, 1985 V4 Johnson 120hp with a V6 gear case -
1971 23' Glastron V234 - Yamaha 5.0 litre V8 260hp "Drifter II" |
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Homeport: Massapequa NY
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surprise
RO# 7728
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Posted - Aug 07 2010 : 06:51:42
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Probably a little better to be a bit over rated WOT than under it, but you are close enough, I wouldn't worry about it. I'll bet that on a given day, the WOT will vary a bit, the new prop is no doubt somewhat different from the old one, that's probably the reason for the difference, the air temperature, fuel and whatever else load, and how well you have tweaked the trim at WOT will all affect the RPM. Enjoy the boat.
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Homeport: Hayes, Va.
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BoatCrazy
RO# 30843
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Posted - Aug 07 2010 : 07:51:17
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Thats a good point. I knew that trim and weight would affect WOT, but I never took it into consideration with this issue now.. I guess its not an issue.
As far as I am concerned, this is a CLOSED issue.
Thanks all!!!
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1990 Searay Sundancer 310 twin 5.7 mercs Alpha I's "Victim Of Fate"
1988 18' Anacapri Center Console, 1985 V4 Johnson 120hp with a V6 gear case -
1971 23' Glastron V234 - Yamaha 5.0 litre V8 260hp "Drifter II" |
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Homeport: Massapequa NY
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Not reaching RPMs
