'89 V135 Low RPM

Webenew

Recruit
Joined
Jul 14, 2008
Messages
5
'89 Searay 180 with V135 s/n c166937. Max RPM is 3500 and will intermittently jump up to 5600 at WOT while cutting in and out. I?ve eliminated stator, switch boxes and coils as possible cause and trigger checks good. Also replaced fuel pump, filter & lines and cleaned carburetors and installed new gaskets/needles & seats. Good spark on all cylinders. Looking for hints on what non-typical failure might be causing this problem. Thanks in advance.
 

Laddies

Banned
Joined
Sep 10, 2004
Messages
12,218
Re: '89 V135 Low RPM

Have you checked the switch box bias circurt and the rectifier? Also a bad high speed winding in the stator will act that way and have good spark at idle and mid range, how have you tested the system with a DVA, because a OHM meter means nothing with the type of problem your having.
 

Webenew

Recruit
Joined
Jul 14, 2008
Messages
5
Re: '89 V135 Low RPM

Bias circuit & rectifer good. I found all cylinders have good spark at idle but #3 & #5 have drop out at partial throttle. DVA checks of stator look good. Thanks in advance!
 

Webenew

Recruit
Joined
Jul 14, 2008
Messages
5
Re: '89 V135 Low RPM

Correction...#3 & #6 (not #5) drop out at partial throttle.
Thanks
 

Laddies

Banned
Joined
Sep 10, 2004
Messages
12,218
Re: '89 V135 Low RPM

In as much as 3&6 have no common part in the ign system you need to check for a voltage spike in both the ign system and the charging system while running the engine, it should show just before or at the time the miss occurs. It could be something as simple as a bad connection, it doesn't have to be a bad component.
 

Webenew

Recruit
Joined
Jul 14, 2008
Messages
5
Re: '89 V135 Low RPM

Since the problem was related to throttle movement I checked the trigger first. I disconnected wires from the switch boxes and all ohm readings were good. I checked each wire to ground and found intermittent continuity when I advanced the throttle. I couldn't determine where the short was located. I adjusted the trigger harness by moving the harness clamp and found I could eliminate the short. I'll replace the trigger at a later date but but for now its running great...it's usually something simple, huh?
Thanks!
 

j_martin

Admiral
Joined
Sep 22, 2006
Messages
7,474
Re: '89 V135 Low RPM

Correction, 3 and 6 share a trigger coil.

Check the trigger harness for damage where it comes out from under the flywheel. A neat splice and adhesive lined heat shrink will fix it.

Been there, done that.

hope it helps
John
 

sschefer

Rear Admiral
Joined
Nov 13, 2008
Messages
4,530
Re: '89 V135 Low RPM

Just thought this might show where to look for a short. The trigger wire cover can wear through or melt as this one has.
EngineRebuild039.jpg
 
Top