1998 Mercury 200 EFI

**DieselDood** · 09-05-2023, 03:56 PM

1998 200EFI. Serial number: 0g570271

I just got the boat that it's on. The motor didn't run when I bought it but Compression is good, and leak down was good, so I took a chance.
One switchbox later and it runs great... except.

Cold, it idles great. (My habit, I back in, drop boat. Start it, let it idle while I park the truck, so the motor is mostly warmed up) Drop it in gear and... feel free to move about the lake.
I fish for a bit, then fire it back up and it will idle, but I drop it in gear and it dies. I give it just a TOUCH of throttle and it is OK when I drop it in gear.
If I come off the throttle too fast it will die too.

Sadly the tach is not currently working (one of the first projects to tackle) so I don't know what the base idle RPM is currently cold or hot. It does sound lower than my Carbed 1997 200, that I have set at 900rpm. But this whole motor sounds much quieter. The Carbed motor is the boxy looking cover and this EFI is the more smooth aerodynamic cover. I believe on my Carbed motor it has 2 holes for exhaust to exit right at about the water line, so I believe that is why it's louder.

Anyway....
Is there an easy adjustment or do I need to be very careful on making an adjustment to this motor? I'm pretty familiar with the Carb motor and what needs to be done, but the EFI is a new animal to me.

Thanks!

**XstreamVking** · 09-05-2023, 05:45 PM

Adj. the throttle arm stop for more idle r's. Same as a carb engine.

**LakeFever** · 09-06-2023, 06:11 AM

New reeds and lap the cages while their out wouldnt hurt. My stock stainless reeds had huge gaps when i swapped em

**DieselDood** · 09-06-2023, 08:30 AM

Originally Posted by LakeFever

New reeds and lap the cages while their out wouldn't hurt. My stock stainless reeds had huge gaps when i swapped em

This winter I may try to pick up a set of Boysen reeds for it.
Do stuffers help on these? I put them on my Carb'ed motor and I like them.
I'm also struggling a little to get on plane with a 25P prop (boat is kinda "rare" as it has a factory 200hp, 98% of these have 225s)
If I had more free time, I'd swap motors just to see the difference before I sell my other boat. 200EFI vs 200 Carb'ed with reeds and stuffers. lol

Thanks for letting me know the adjustment is simple and not a big deal. I'll give that a little twist once I get the tach fixed, so I know what the heck is going on.

**pcrussell50** · 09-06-2023, 01:24 PM

Originally Posted by DieselDood

This winter I may try to pick up a set of Boysen reeds for it.

Curious... Why Boysen reeds and not Chris Carson reeds?

===

Originally Posted by XstreamVking

Adj. the throttle arm stop for more idle r's. Same as a carb engine.

I always thought you do idle speed on carb motors by way of small tweaks of the idle timing stop? In fact at least one of the legends around here, is partial to leaving a small gap between the throttle cam and the roller for the butterflies.

===

I wonder if the OP might have an issue with his TP throttle position sensor?

-Peter

**DieselDood** · 09-06-2023, 02:20 PM

Originally Posted by pcrussell50

Curious... Why Boysen reeds and not Chris Carson reeds?

-Peter

I used CCMS on my Carbed motor.
The stufferers didn't fit. I had to grind and modify them significantly to get them to actually fit. It was like they got rough cut and were waiting for the final fitment cut and were sent to me on accident. I called before I modified them and got no answer or call back.

Then 2.5 months later I had one Reed start to come apart giving me a lack of power. I reached out to him multiple times and again got no answer.

So, sadly I'm not terribly impressed with his product or customer service at this point. I dont like to say bad things about companies on the internet, unless it's extremely bad. This was close for me, but just shy of my threshold.

Although, you asked, so I will tell.

**XstreamVking** · 09-06-2023, 02:22 PM

Sometimes all you have to do to adj idle is take the slack out of the cable at the adjuster. Idle change should not move things enough to effect the TPS. Really, it should start, idle, and keep running at 800 r's. Idle timing should be checked as it changes idle speed also. I have 3 of the same model engine. The idle stop gap should be big enough to slip in/out a pc. of note book paper. Gap at butterfly roller to cam is as you said a small visual gap. 1/16-1/8. I start with idle timing, check roller gap, and finally adj cable and arm gap.