Low engine power during break-in period?

[silver_power]

Hello, is there a possibility the ecu of a new sterndrive engine (ex 350mag mpi 2009) to control (set a limit) the power of the engine during break-in period, just for protection? I am asking just because my brand new 350mag has a lot of power during acceleration (boat on plane), MUCH stronger than my old engine (5.7LX 4bbl) but at the range 3500-4100rpm (till there i pushed it for about 30sec as it has only 3,5 operating hours), seems to have less power than my old engine. And so, i thought maybe this happens electronicaly, from the ecu for protection. My boat is a wellcraft nova spyder 202, with 22p enertia.The same prop i had also with my old engine.Do you know if this thought may hapens?

 

[Philster]

Re: Low engine power during break-in period?

Engine Comp won't limit the power during break in.

How can you feel if it has more power? Once at that RPM range, if it holds the RPMs you want, then it truly has the power. If you are trying to pull/accelerate at that RPM range, you would have to feel (or measure) its sluggishness.

For the record, different engines have different power curves. Also, the fuel injection might be programmed to be more efficient at cruising speeds. This might give the sensation of being less powerful.

As engine speed builds with carbed engines, the carb/engine just demands (through sheer physics) more fuel and you need to back off to restrict the fuel flow. This can lead to a sensation of a carbed engine being more powerful as you are literally pulling back on throttle to restrict the sucking power of the carb/intake/engine as revs build.

The engine comp has some learning/adjusting to do, to. I say to break 'er in properly and then note time-to-plane performance, fuel efficiency and overall top speed. I will bet all numbers are equal or better. If you can match all numbers and get better mileage then this equals a win for MPI.

 

[silver_power]

Re: Low engine power during break-in period?

My old engine had about 600hrs of operation, 235hp@prop, and with enertia 22p reached with 2persons 4500-4550rpms. Now the 350mag mpi has 300hp@prop and with the same prop and load, i expect to reach about 5100rpm.But if i judge from the way it accelerated from 3700 to 4100, i dissapointed so to think that this engine would not reach even 4600rpm if i had to push it. Concerning the time to plane, there is no camparison. The new engine accelerates A LOT quicker and with the half way of the throttle control the time that with the old engine i had to push for at least about 1-2sec(depending load) at wot and then push the throttle back for cruise. All these with the same prop.After some hours there will be so much difference at high revs?

 

[Philster]

Re: Low engine power during break-in period?

You won't know until you do run at WOT, so wait til then. You are speculating based on feel between a narrow RPM range that it won't hit 4600 RPM some day.

Break 'er in right and then report back when you run at WOT and note the RPMs and anything else you can.

We could speculate all day about what might happen when you finally do test WOT performance.

 

[silver_power]

Re: Low engine power during break-in period?

Ok my friend, thank you very much.
I will come again as soon as the break-in period will expire and go to wot.
But till now i can say for sure that MPI is clear winner concerning the fuel economy. Smartcraft screen showed 1.0miles/litre (3,78mpg)@3300 and 37mph. This was something that maked me happy during my first ride with this engine last Saturday!

 

[silver_power]

Re: Low engine power during break-in period?

Hello again,
I am still in break -in period and i am sure that i operate the boat according the break-in instructions. Well yesterday, after i completed the first 11,5hours of the engine, i decided to push it to wot for a while. Besides after the first 10 hours i can do it for small time periods. So i was alone, with about 40gal of gas and 10gal of fresh water at the back. The boat wet on plane very fast and only with the half way throtle. I then accelerated with 200rpms step till the wot. I dissapointed.... i could reach only 4300rpms and about 53mph on GPS.I push it for about a minute, i did not want to push it any more.The fuel pressure at smartcraft tacho display was 2,96bar (ok) the temp 72oC degrees and everything was just fine.....The digital rpm said 4280-4300rpms. This range is A LOT AWAY than normal range of the engine (4800-5200). With my old engine (5.7lt with 235hp@prop) the boat was hitting 55mph@GPS and 4500rpms WITH THE SAME PROP!! (22p Enertia).
Now with +65hp@prop i could not reach even 4500!! Is there a case that after 10-20-30 operation hours i could gain +500-900 rpms? My experience sais NO! I started to think about wrong prop pitch, but then i thought that i must use 15-17pitch to reach 5000-5200!!!!! So i rejected it. After all, with the old engine i had 22p Enertia, and now with the new i will go to 17p?!! I do not think so. Is there a possibility, the tacho (rpm) not to be accurate? ...But it is Smartcraft....i do not know what to think.
The boat is Wellcraft 202 Nova Spyder with 350Mag Mpi (MD 6/2009)!
I also used petrol from 2 different gas stations, so i do not think it is fuel problem.
What do you suggest me to do? And what should i expect after some hours of operation.? I am confused beacuse the new engine gives me the impression that it has about 20hp LESS that my old 600hrs 5.7l!!!
I am now thinking to put the 21p aluminium prop which the factory gave me when i bought the boat, for the next hours !

 

[silver_power]

Re: Low engine power during break-in period?

Anybody with similar experience....???

 

[fossill]

Re: Low engine power during break-in period?

Mercruiser service manual #24 for GM small block 5.0 and 5.7L engines shows normal WOT rpm at 4400 to 4800 rpm for all engines carb, efi, and mpi. I don't think you have a problem. Your engine is running fine according to the book. Once she breaks in it should gain that extra 100 to 200 rpm. I would drop the prop pitch by 1 though to get it closer to the upper normal limit of 4800rpm going by your old max rpm of 4500 with your current prop which this engine should also do once broke in.

 

[silver_power]

Re: Low engine power during break-in period?

I do not think the fact that a Brand NEW 2009 350mag mpi has lower performance than a 1993 5,7lx with 235hp@prop, and 600 operation hours.My old engine had 4200-4600rpm (according to the label on the flame arrestor) and could hit 55mph@4500. The new engine with 11,5hrs hit only 53mph@4300 and it DEFINATELY normally runs at 4800-5200rpm according mercury site and the label on the flame arrestor. So i think that 1) something bad happens OR 2) i will gain about 500-700rpm after 20-30 hrs....which i doubt it....
That is why i am asking if someone has similar experience. How much difference (in rpms) is between an engine with 10hrs and an engine with 50hrs?

 

[jtmarten]

Re: Low engine power during break-in period?

Your 11.5hr MPI isn't making 300hp at the prop YET. It may need an additional 10-20hrs of run time to fully break-in, and most likely you're going to have to make adjustments to the fuel injection map to optimize power.

 

[silver_power]

Re: Low engine power during break-in period?

I believe that what you say. I do not expect from the new engine to produce 300@prop yet but judging from the performance, i think for now it produces about 10-20hp LESS than the previous engine. What do you mean saying that after break-in i will have to make fuel maping adjustments? I will do it or the ECU by itself?? I hope the second. You mean the engine after about 20-30 hrs will produce +50-70 more hp?

 

[fossill]

Re: Low engine power during break-in period?

You may want to find out why the wot rpm discrepancy between the official Merc service manual and that sticker or label on the flame arrestor unless it got updated later on. You probably will have to reprop that thing if indeed it requires 5200rpm as the orginal prop set up was for a 4800 rpm max. One thing to keep in mind is exactly at what rpm that it will be making that 300HP, which is usually at it max rated rpm. Sorry, can't help you out.

 

[Philster]

Re: Low engine power during break-in period?

Talk to me about your fuel pump....

You went from carbed to injected. As a percentage of the engine's original power rating, you boosted the peak HP by 28%. Fuel pump different?

Talk to me about trimming out:

Are you trimming out as far as you used to? If you go by a gauge, are you certain the gauge is dead on mark as it was before?

 

[silver_power]

Re: Low engine power during break-in period?

As i have totaly repowered my boat the fuel pump has also been changed. The new engine has new-style electric fuel pump which is operated with the turn of the key before the engine starts. And it is part of the engine. The new engine came with the new fuel pump. And i checked the fuel pressure, it the same 2,96bar at idle and at wot.
Concerning the trim, yes, i trimed all the way up. .......
I am very confused and dissapointed! That is why i am asking.......
I think the only way to go at the range of 5000rpms is to put 15-17p propeller which i think is VERY small!
I had 22p with the old 235hp engine and now with 300hp i will put 15???

 

[silver_power]

Re: Low engine power during break-in period?

As i installed the engine (complete package) myself, is it possible to make something wrong and so the engine not to perform as it should be? The throtle cables are ok and open the throtle plate full when i go to wot. I have checked that before i test the boat in to the sea. There are no vibrations during the operation of the engine, everything is smooth and quiet....but no RPMs . The fuel seems to be enough as the fuel pressure does not drop at any rpms (2,96bar)....so i think i will have to wait the engine to make any adjustments, calibrations or anything else. Till then i will change the 22P Enertia with an 21P aluminium . What do you think?

 

[silver_power]

Re: Low engine power during break-in period?

I found a 19P aluminium prop. I am going to put it instead of 22Enertia. With this prop i hope i will go to 4800rpms. Is there a problem to rotate the engine at 4800 with only 12hrs? or i better no to push it to this range?

 

[fossill]

Re: Low engine power during break-in period?

Nope, you can go full bore if you want. I believe the manual says to take it there in increments of a couple of hundred rpm instead of slaming the throttle forward.

 

[silver_power]

Re: Low engine power during break-in period?

Yes, that is true. That is what it says. I will post after this weekend.
Thank you very much.

 

[silver_power]

Re: Low engine power during break-in period?

Update: After my dissapointment with the performance (53mph@4300 rpm). The engine now has completed 16,5hrs and i can tell for sure that i have started to feel happy. After +5hrs of normal cruise according break-in instructions, i pushed it to wot with 200rpm incements. Result 56mph-gps@4580rpm. So after 5hrs the engine reached +280rpm and +3mph. I beleive that at the end i will reach 5000-5100 rpms. I am still running the 22P Enertia despite the fact the engine is out of normal rpm range (4800-5200rpm). Besides i do not push is so far and i mostly cruise (2800-3300rpms), so with the 22p i have very good economy.The fuel economy is awesome ....3,78mpg@34-43mph constant! I think that this engined perfectly matched with the boat!!

 

[John_S]

Re: Low engine power during break-in period?

Please provide updates as your engine continues to break-in.