Mercury Sportjet 90 bogs past 4K

[milehighboater]

Re: Mercury Sportjet 90 bogs past 4K

Craig:

Keep in mind that the Tracker is actually a Mercury outboard, whereas the Sportjet 90 and 120 are a Force powerhead. The engines are nothing alike. Although they both have 3 cylinders, they have different CID.

Craig

Your right, I have a tracker marine with a force block, but merc set-up with three carbs. a 98 still has the 3 cyl force but with the single force carb. Those motors get tricky in the later years.

 

[Craig-]

Re: Mercury Sportjet 90 bogs past 4K

Keep in mind that the Tracker is actually a Mercury outboard, whereas the Sportjet 90 and 120 are a Force powerhead. The engines are nothing alike. Although they both have 3 cylinders, they have different CID.

A carburetor is a carburetor, doesn't matter what it is on. They all rely on fuel/air delivery and atmospheric pressure. Modern electrically controlled ignitions all operate on the same basic principal as each other.

 

[milehighboater]

Re: Mercury Sportjet 90 bogs past 4K

A carburetor is a carburetor, doesn't matter what it is on. They all rely on fuel/air delivery and atmospheric pressure. Modern electrically controlled ignitions all operate on the same basic principal as each other.

Yep, I'm just saying "I have a 1998 force" is not enough. They put many different ignition and fuel set-ups on these later year Forces. S/N help out alot.

 

[Craig-]

Re: Mercury Sportjet 90 bogs past 4K

Yep, I'm just saying "I have a 1998 force" is not enough. They put many different ignition and fuel set-ups on these later year Forces. S/N help out alot.

Force motors (Chrysler block) never were very good, few will argue with that.

 

[SeaRayder4]

Re: Mercury Sportjet 90 bogs past 4K

Charlie, Craig & ALL - I'm EXCITED to report a solution to this 10+week saga of learning and frustration.

THE NEW DESIGN FLOATS WERE THE PROBLEM. The newer stock number F10346 are not the same floats as 891730A01. You can see in the pic several differences in design, mainly a tab near the pin that keeps them from falling all the way the bottom of the bowl, but more importantly, the dimple near the main jet (Charlie - wow you're good) that prevents the float from blocking fuel flow.

Here's a link to the YouTube running video with credit of thanks to this website.

http://www.youtube.com/watch?v=mTaB4NlmLgI

I've learned so much these past 10 weeks on this project. I promised to post a resolution because Google is "full of problems with no answers". I appreciate you all sticking with me while I learned and found a solution. Who knows how much money would have been spent and if I ever would have found a solution without all your input.

I'm guessing I have 100+ hours in this project, researching, testing, trying, and repeating the process over and over. Was it worth it? When I heard this engine that I built FINALLY run smooth and with the power of a new one...it was an easy conclusion. Now if I get a few "trouble-free" seasons out of it - that would really make it GREAT

Now it's time to enjoy the boat before the snow flies! The kids are smilin'.

With many thanks...I'll continue to spread the word about this site!

George

P.S. - I'll stick check compression next time I'm out and post a followup. I was too excited to unplug anything that was working right now. Timing is set dead-on a 30 degrees WOT.

 

[Craig-]

Re: Mercury Sportjet 90 bogs past 4K

...mainly a tab near the pin that keeps them from falling all the way to the bottom of the bowl...

The float doesn't need to fall to the bottom, just enough to pull the inlet needle fully open. The inlet needle should be engaged to the float tab with clip in order to be pulled.

You can see in the pic several differences in design, ...the dimple near the main jet that prevents the float from blocking fuel flow.

Are you saying when the float dropped, the float restricted the fuel pick-up at the main jet, at the arrow in attached photo? Did it actually touch?

You should alert the rebuild-kit maker of this issue. The motor sounds good in video, most important that no damage was done due to head gasket leak. Well done.

 

[SeaRayder4]

Re: Mercury Sportjet 90 bogs past 4K

Thanks Craig - yup the motor does sound good and I surely don't need any more engine problems for a while. I ran about 6 miles at various throttle settings and checked the plugs at the half-way point. Minimal carbon deposits but most importantly all 3 plugs looked the same. I'm guessing I'll see some carbon for a while since this engine really hasn't had the chance to burn off any since the breakin. I'll be keeping a close eye on the plugs after each lake trip to be sure nothing is running lean. I was told if I really want long life out of this engine to retard the timing to 28 (instead of 30), use 89 octane, and Merc synthetic blend oil. I'll lose a little performance but I would love about 500 hours between rebuilds (if that's possible).

As far as the floats - I'm attaching a few more pics to further explain the problem. They were purchased from Boats.net and there was a service bulletin in the floats F10346 that said they were replacing 891730A01 (the correct float). I'll contact Merc to alert them of the issue for sure. There is not a spring clip connecting the float to the needle (like there is on my Lawnboy). It apparently just relies on gravity to pull it down. But the F10346 is missing the dimples so it blocks the fuel flow to the main jet when the bowl is filling? Also, the missing tab that prevents it from falling all the way down to the bottom of the bowl. There are small tabs present on the F10346 if you flip it over, but after inserting the pivot pin to hold it in place, it doesn't allow for the needle to fully depress when closed. It is also not adjustable for float level.

I found some NOS 891730A01's on Ebay that I just ordered for stock in case I need them in a few years.

Wow this has been a learning journey . Many times I was ready to "throw in the shop rag" and order the $4000 fully dressed powerhead and end this! All in all with the testing parts I had in stock from the duplicate engine that I have (that needs the shortblock rebuilt), my total $$ investment to solve this was $0. Sure wish I had the 10 weeks of summer back, but there's still about 7 weeks of good fishing here in Ohio and I told the kids they could where a wetsuit for kneeboarding.

Thanks again for all your advice and tutorials on how stuff works on this engine. I feel now I can handle just about anything it throws at me....(maybe I shouldn't of said that).

All for now. I'll post some compression numbers next week.

George

 

[SeaRayder4]

Re: Mercury Sportjet 90 bogs past 4K

2hours kneeboarding with the kids last night and THANKFULLY the motor ran strong - held RPM without a hickup. Hopefully a few more days like this left in our Ohio season. Water temps are already down to 73F.

 

[SeaRayder4]

Re: Mercury Sportjet 90 bogs past 4K

8 more hours of run time the past few days with visiting relatives and thankfully still the engine runs strong and smooth at all RPM's.

This was especially helpful as we stared into the "eye of a major pop-up Central Ohio Storm" with hail, lightning, and 70mph winds...and made it back to the launch at WOT - "just in time"...

Thanks again everyone - will post compression #'s soon.

 

[Craig-]

Re: Mercury Sportjet 90 bogs past 4K

great

 

[mikeneal]

Re: Mercury Sportjet 90 bogs past 4K

Good too hear still running like a champ. You went thru quite the process. At least it is satisfying to hear it run perfect after all the trials and tribulations.

 

[SeaRayder4]

Some Compression Numbers

Some Compression Numbers

Been having too much fun with a boat that's running great to post any updates!

Just winterized the boat after a very successful fall muskie fishing season including 2 40's and a 46"er and checked the compression.

Top = 135
Middle = 140
Bottom = 140

So....I'm thrilled to see the engine is wearing great. The plugs all look the same, the only problem I'll address in the spring is too much smoke after a period of idle or no wake speeds. I did get NEW floats that are the same EXACTLY as the old ones (with the dimples and same part number), so I'll update next spring with that improvement.

But, I want to wait until after a couple of trips next spring cause if something messes up I want to be sure I know exactly what caused it . Turning right at 4900rpm WOT with speed of 34gps and considering how much weight I've added to my boat with fishing gear, I'm very happy.

From Ohio, I bid you all a fast winter season. To you southern boaters....think of me fishing on my Wii...

Thanks again to everyone who made the last 2 months some of the best I've ever had including my 75-year-old dad getting his first muskie.

http://www.ohiogamefishing.com/community/showthread.php?t=157839


George

 

[Craig-]

Re: Mercury Sportjet 90 bogs past 4K

Sounds good George and congrats to your Dad.

As far as the excess smoke goes, not to worry pretty typical. Don't over oil the premix, err on the light side.

Happy Holidays