Low RPM at WOT again !

[Elkhunter173]

I have a Mercury 1988 v150 black max. I have researched past forums for a couple months now and no luck. Give me some new ideas.

Let me start from the beginning. In 2008-2009 I had the same problem but intermittant. After the motor would warm up I could get 6000 rpm at WOT. If I let it set for 30 min it would only get up to 4800 rpm. I would have to stop the motor and shut engine off several times and the finnaly get the rpms back up to 6000 rpm,s. Thanks to you guys I replaced both switch box's and the problem was solved. Thanks

Last July 2010 I was pulling two tubes with four kids on the tubes and two adults and three children in the boat. After about 1 hour The motor lost power and would barely run dropping the rpm to 3800 rpm. I lost spark on the #5 and #6 coils. I replaced coils and the rpms came up to 4800 rpm's and both coils had spark. I replaced the stator and trigger, checked compression 105 psi on all cylinders, carbs where cleaned and rebuilt. I have spark on all cylinders.

I am reluctant at putting new switch boxs in again. Could a rectifier or voltage regulator be causing this problem by not getting enough voltage to the coils? I have not checked the reed valves but it is not spitting out any fuel from the carbs. What do you think I should check next. I do not have a dva meter but I might just have to get one if I need it.

 

[Mi duckdown]

Re: Low RPM at WOT again !

Yah a DVA meter, and an OEM merc Manual will be your best friend

 

[Elkhunter173]

Re: Low RPM at WOT again !

I have an OEM manual and the DVA is on its way. I

In the dark last night I went back to my old checks for a miss with a timing light. I found that I do have a miss on the #2 cylinder about every 3 seconds and a miss on the #4 cyl every 5 seconds. I replaced the outside switch box with an old one from 2 years ago and I wasn't sure if it was good or not. When I hooked up the old one I had consistant spark on the #2 missing on the #4 and no spark on the #6. I am guessing bad switch box? ordering two tommarow or do you think just the one would be fine since the inside switch box is only 2 years old?

My new question is what would make two coils burn out #6 and #5 and the outside switch box that controls the even side miss on two different cyl #2 and # 4 ???

My motor 1988 v150 black max has a rectifier and a voltage regulator that hooks up to the rectifier. Is this the voltage regulator that will bleed off any access volts and do I need it they are pretty spendy. Thanks for any help!!!

 

[j_martin]

Re: Low RPM at WOT again !

To answer your question, either general overheat, or moisture in storage.

The switchboxes don't get any power from the 12 V side. They have their own charge coils in the stator. It is possible for overload on the 12V side, especially with overheating added in, to cause the entire stator to deteriorate.

Like he said, a DVA and a manual are your best friends.

The regulator is NLA because it is a fire starter and is not needed. The battery, with reasonable maintenance will hold the voltage within specification. If you want to put parts in the 12V side, put a 20 amp regulator from a later engine in place of the rectifier. Mounting adaption will be needed. If you want to just put in a good rectifier, buy a commodity 20 amp 200V or better bridge rectifier and fit it in. It will actually last awhile.

 

[Elkhunter173]

Re: Low RPM at WOT again !

Thanks J_Martin.

I was hoping you would reply you know your $&!^. I have always kept my boat inside however I do leave it in the water over night every now and then.

I will disconnect the regulator tonight and pull it off if it can cause a fire.

I am about to order two more switch boxes tommarrow unless you think the other one I bought two years ago would be fine. the cylinders 1 3 5 are all hitting fine. I dont mind putting a little money in it because maintenance is a must on all vehicles and things wear out after 23 years. I just dont like ordering them again after it is two years old unless you think I really should.

Thanks again J_Martin iboats forum wouldn't be the same without your knowledge and your humor.