mercury 120hp sportjet rpms @3000 wot

jdnelson

Cadet
Joined
Jul 4, 2003
Messages
10
I have a 1995 Searayder with a 120hp mercury sportjet. It only has about 145 hours on it. I cant get it above 3000rpm. The bottom 2 spark plugs are wet. I have replaced the plugs, swapped out the plug wires and replaced the bottom two coils. They spark, but maybe not enough? Early on I removed the carbs and went through. All jets seemed clean as a whistle. Do I have a switch box problem or stator? <br />Thanks.
 

B_Eager

Petty Officer 2nd Class
Joined
Feb 12, 2003
Messages
109
Re: mercury 120hp sportjet rpms @3000 wot

I Have a 1999 Sugar Sand Super Sport.<br />The lower two plugs are always wet. Do you idel alot?? Do you bypass the auto enricher when the boat is warm?
 

jdnelson

Cadet
Joined
Jul 4, 2003
Messages
10
Re: mercury 120hp sportjet rpms @3000 wot

I don't idle excessively, but i don't think my bottom two cylinders are firing properly. I can't get above 3000 rpm. I don't have the enricher you speak of.
 

zzzzz

Lieutenant Junior Grade
Joined
Jan 13, 2003
Messages
1,094
Re: mercury 120hp sportjet rpms @3000 wot

Jeff- first check for correct plugs..Champion L76V or QL76V..I think you might want to consider using a qualified shop because randomly replacing electrical components gets expensive quick..switchbox=$225...stator=$125 :cool:
 

jdnelson

Cadet
Joined
Jul 4, 2003
Messages
10
Re: mercury 120hp sportjet rpms @3000 wot

I may do that. All 4 plugs are new autolite. There was no change in the performance after plug change. It was not properly firing on those cylinders before plug change. Top two continue performing properly regardless of old or new plugs. Old plugs were original with 145 hours on them.
 

Northern Eclipse

Senior Chief Petty Officer
Joined
Jun 24, 2003
Messages
665
Re: mercury 120hp sportjet rpms @3000 wot

Hey Jeff I once had a similar problem with a Sea Doo What I found was I sucked a chunk of old rope that was wrapped round the impeller, Machine would idle a start fine but not get any rpms.. this is just a thought if you have not looked at the pump....
 

jdnelson

Cadet
Joined
Jul 4, 2003
Messages
10
Re: mercury 120hp sportjet rpms @3000 wot

I did check the impeller. I have tested the fire on the two cylinders and they are just going along for the ride. If I pull either of the top two plug wires, the motor dies. The bottom two cause no change.
 

B_Eager

Petty Officer 2nd Class
Joined
Feb 12, 2003
Messages
109
Re: mercury 120hp sportjet rpms @3000 wot

Do you want the test specs to check these items. The mercury manual is long winded, but I have the data to the 1999 120 xr2 unit. Motor is almost the same, all the changed was the fuel pump and the auto enrichment system. Is the lower carburator out of adjustment?? (rich)
 

jdnelson

Cadet
Joined
Jul 4, 2003
Messages
10
Re: mercury 120hp sportjet rpms @3000 wot

Wave Hopper,<br /><br />I would love to get the specs from the manual. One of the early things I did was pull the carbs and go through them and found nothing out of the ordinary. Actually they were real clean. I reset the idle mixture per the manual. The performance problem I am having has not changed with everything I have done so far. Carbs, plugs, wires, new coils. I'm nearly convinced I have a bad connection from the switchbox, a switchbox problem or stator. <br /><br />thanks,<br /><br />Jeff
 

B_Eager

Petty Officer 2nd Class
Joined
Feb 12, 2003
Messages
109
Re: mercury 120hp sportjet rpms @3000 wot

The best way to give you specs is one of two ways.Be specific on what you want to check first, or give me you email and I'll send you some pages from the book.
 

jdnelson

Cadet
Joined
Jul 4, 2003
Messages
10
Re: mercury 120hp sportjet rpms @3000 wot

Once I go through the connections to and from the switchbox, I guess I'll be checking power coming from the switchbox to the coils. <br />My email is jeff.nelson@mstar2.net.<br /><br />thanks
 
Top