Mercruiser 4.5L 250hp - Anybody else have it and what are your opinions so far?

[jwdavis28]

Mine has roughly 15 hours on it now with no issues (as you would hope!). This is my first I/O as all previous experience was strictly with outboards.

First impressions are great. Quiet, sounds awesome when opened up. Accelerates very nicely. Is producing good top end numbers for a deck boat (looking at different props so this could go up or down).

Since it's a new motor I thought a thread might help if anyone else is considering this engine.

 

[achris]

As much as I like the idea of an all Merc engine, I have issue with their parts pricing. I'll stick with a GM based product so I can outsource my parts supply. As an example, my oil pan needed replacing a few years ago. Merc wanted over $700 for it. I got it online from a GM parts supplier for $159. That was brand new delivered to my door. The oil pan gasket was $9.90, Mercs' asking price is $85.

Hope your engine keeps performing well for you, and thanks for the report.

Chris......

 

[jwdavis28]

Well for new boats you may not have an option going forward as GM & others drop a lot of the current blocks that are used by the marine industry. They are dropping them due to old technology that is dragging down the efficiency of the overall company as they try to comply with the new regs.

Bottom line is that Merc is a big supplier of power in the marine industry and this motor is the start of this. Several references are out there that others besides Tahoe are already redesigning their hulls to accommodate the newly developed marine specific motors.

 

[thumpar]

I wish Merc would have marinized the GM 5.3l. It is rock solid.

 

[Jmunk]

I wish Merc would have marinized the GM 5.3l. It is rock solid.

I have questioned that myself for years.

 

[bruceb58]

I wish Merc would have marinized the GM 5.3l. It is rock solid.

As long as the 5.7L is still available they would never do that. 5.7 has more torque at lower RPM.

 

[jwdavis28]

I also saw a reference that has Merc building a V8 version of my 4.5L. Could be potent.

 

[GA_Boater]

As long as the 5.7L is still available they would never do that. 5.7 has more torque at lower RPM.

Mercury no longer offers the 5.7. The current range is 8.2, 6.2, the new 4.5, 4.3 and 3.0.

 

[thumpar]

And the 6.2 is a merc design not a gm base.

 

[bruceb58]

Mercury no longer offers the 5.7. The current range is 8.2, 6.2, the new 4.5, 4.3 and 3.0.

Looks like Volvo still offers the 5.7...they actually have a 5.3 now.

 

[thumpar]

I saw that Volvo had a 5.3l but didn't know it was an inhouse engine or based on the GM.

 

[GA_Boater]

Looks like Volvo still offers the 5.7...they actually have a 5.3 now.

I thought we were talking Mercruisers. :wink: LOL

 

[bruceb58]

I thought we were talking Mercruisers. :wink: LOL

We are...was surprised they dropped the 5.7 and just noted what Volvo had.

 

[jwdavis28]

I believe that the first version of this new motor was Merc's 4.3L 220hp model. While it's a 4.3 it's not a GM based design.

 

[thumpar]

Have you ever been in a boat with a GM based Merc 250hp? I am wondering how they compare.

 

[jwdavis28]

Have you ever been in a boat with a GM based Merc 250hp? I am wondering how they compare.

I have but it wouldn't be a fair comparison overall as the boat was about 2.5ft longer and heavier than my boat. What I can tell you is that this motor is considerably quieter but that's about all I can compare.

 

[jwdavis28]

Interestingly I may need to reprop this motor (was considering the switch to stainless anyway) as I'm now through the break in period and can turn almost 5500 rpms and the top of the range is supposed to be 5200. I backed off when I saw this happening. Currently propped with a 19p aluminum. Not sure if the motor is making more hp than spec'd (I doubt it) or if the 19p prop just isn't right. Either way the motor is performing very nicely so far.

 

[thumpar]

You may be able to jump to a 23 pitch. The hole shot will not be as good but it will fly on the top end. A 21 pitch might be a good compromise. Another thing you could do is just get the 23 and use the 19 when you want to tow people. Some prop shops will let you try out different props so you could find what works best without buying props you don't use.

 

[jwdavis28]

thumpar. yeah I could go to a 21p aluminum but really want to change to stainless. I would normally look at a 17p stainless but not sure now.

 

[HT32BSX115]

Interestingly I may need to reprop this motor (was considering the switch to stainless anyway) as I'm now through the break in period and can turn almost 5500 rpms and the top of the range is supposed to be 5200.

Since it's still pretty new, I would think the dealer needs to know if it's (really) over speeding.

Couple of things would be factors there. ALL the new engines these days have rev limiters built right into the IGN systems. My 97 7.4L V-8 (Thunderbird-V IGN) rev limits at 4700 RPM (max recommended engine RPM is 4600)

if yours is making it to 5500, and the rev limiter is working, I would suspect the TACH being defective before believing it's actually turning that fast!

The dealer might also be able to tell you where the REV limiter actually stops the engine from turning faster (maybe it's 5500) , but since tachometers are frequently wrong at higher RPM, I would verify the tach before buying props.