Nephew has a TR20 that we just had the ECM repaired on. Running a lot better but now it has issues getting up on pad in a timely manner. Takes about 25-30 seconds and stalls around 2100 rpms. We took it back home and ran it on the rabbit ears and it would rev up just fine. Once it does get on pad max rpms is around 5100 with top speed being around 48mph. Any ideas? It’s a ‘97 mercury xri 200hp outboard.

Before ECM problem motor was running fine. He’s running a 24P 4 blade prop right now.

Thanks for the help.

this been happening since you put tha "revamped" ecu on it?.. how did it act with ecu problem?.. that motor needs ta be turnin' AT LEAST 5800.. first check fire and comp.. if you need an OEM manual send me an email addy and i'll send ya one in pdf...

If the engine isn't firing hot (adequate spark) or is having other power-generation issues, you're rarely going to see that displayed running no-load with water muffs. I assume NOTHING else has been changed about the boat, and it ran much better previoiusly? As in, no other changes like different prop, engine height, etc. What speed and RPM was he running before? with that same prop? Something is still sick. I can't imagine why a boat with a 200 will only do 48mph, unless there's more story we don't know yet....

Could have the switch box bad that controls the ECU

So full story is this boat has been nothing but an issue since he purchased it over a year ago. On his first trip out the power head blew and then it spent 6 months in the shop at Sartin Marine. Once he got it back it ran fine for a bit then the ECM went out and wasn't firing to cylinders 1 and 6. We knew something was wrong as the boat would not go over 6 mph and would not rev past 1500 rpms. So now that he has back from the ECM fix this is what it is doing. He has not changed engine height or prop during any of this but can't speak to what someone did while it was in the shop at two different places (Sartin & N Texas Marine).

This is his first boat and as you can imagine he is beyond frustrated with the entire situation so I am just trying to help him out.

Thanks for the help.

You've now divulged the complex history of this case. Given all you said, I would be suspicious there is a problem that existed somewhere in the past that has never been corrected, and that could be where you are (now) back to. Did your nephew get a mechanic to inspect that motor before he bought the boat, like at least getting a compression check done? It seems very "coincidental" that it blew the first time out. Many anglers have gone 20, even 30 years fishing and never blown one. From whoever rebuilt it, was a root cause determined? Without knowing exactly what caused it and correcting that, little progress is made by putting humpty dumpty back together again.

All good info. Unfortunately even though I told him to have it inspected before buying it excitement got the better of him and he did not do this. Hard lesson to learn for sure for a 22 year old.

I have a 95 200 xri efi, did the same thing and it was a bad coil. it was firing to the block on the back side where you couldn't see it unless the lights were out.

sartin marine found and fixed it for me.

check all your spark at the plug, pull plugs and look for a wet one.

muffs they will run a lot better than on the water since there is no back pressure like when it is submerged.

My 250 Pro XS did the same. It was a bad ignition coil. YouTube it and you can check them yourself with a lighted spark plug tester. Very easy to do.

Update!!!

I gave him my prop to try, 25P Tempest.
Stalled at 3200 rpms but kicked over much faster but still slow. Got rpms up to 5800 but top speed was 41.7

Thanks for the cool ideas, I’ve ordered a lighted spark plug tester to see if that’s an issue also.

tha ecu has nothing ta do with (spark) fire!.. if ya had it turnin' a 25 tempest 5800 @ 41 mph ya got some big problems with whole rig.... sounds like ya need ta start back at square one.. ie: offset, motor height etc..

motor problem can be several things but comp and fire needs ta be first thing checked...

Either tach or speedometer is way off or hub is spun. For these numbers to be correct that would equate to 48% prop slip.

Speed was GPS off graph but I can’t speak to the tach being right or wrong other than it’s a fairly new gauge

If he was reading speed off a GPS there is no way the tach is correct. Does the Tempest have a Flo Torque hub? My experience with a spun hub was no way I was going to get to 41 mph.