2.4L or 2.5L Merc?

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Hi Guys
I am new to the group and must say I am amazed at the knowledge and courtesy here. I am not knowledgeable about this stuff but need some advice. I have a '91 Merc 150HP 2.4L on my bassboat and have Tony Brucato working on converting from carb to injection and then the ACU and SVS system plus a few other things. I have lost about 500RPM's or so and that is why I am doing all of this. I have learned that I need to do a compression and leak down test before going on. Question is, if there needs to be a rebuild or freshening up of the motor would I be better off buying a rebuilt 2.5 L power head instead? This engione has never blown, runs great except for the gradual loss of power. Thanks for listening.

[SFRacing]

welcome to the site.

you will be pleasantly surprised with tony's stuff; tony and linda are good people and wont steer you wrong. Whether you should change 2.4-2.5 depends a bit on what your goal is and what type of boat it is on. Also, what 2.5 are you looking at?

[Specialized P4-12]

if your looking for more ponys you are probably going to spend less money on a used 2.5 200 than you will outfitting that 150 for marginal gains..... the first thing i would do with that motor if it lost 500 rpm would be a spark test make sure all your holes are getting spark... then i would do a compression test.. those 150's are pretty bulletproof.. if you do go with a 2.5 power head you will ned to do some adapting to the mid and exauhst adapter plate.. like put a 2.5 on on there.. but other than that ists pretty straight forward... also you can do alot more with a steel 2.5 block for performance than you can with a 2.4...

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You are right about Tony...he has been a huge help and trying to keep me from spending money needlessly. If the compression test and the leakdown test proves that the 2.4L will need to be rebuilt then I will probably go with a 2.5L 200HP powerhead. Will I need all of the electrical components as well or will all of my electrical from the 2.4L work? I have a Bob's exhaust tuner and solid engine mounts to put on as well. As for what I am trying to accomplish with all of this was well put by Tony to me....Not to get into too many mods so that I don't have a temperamental engine. I am a basser but love the speed and power. My boat is a '91 Astro 18FDX in excellent condition. Rated for 175HP. Thanks to all!! Keep it coming.

[Specialized P4-12]

they will work.. the eltronics are pretty much universal... usualy the only differences between them are the trim relays.. newer motors have more electronic warning systems , but the use a seperate harness.. make sure u change the exaust adapter if you go to a 2.5 a 2.4 will restrict the water flow....

[Specialized P4-12]

i have drilled out the 2.4 adapters wich seems to be ok.. but if you can change it would be best..

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OK...this is getting a little too technical for me. Willing to learn but need time to digest. What would I need to look for and maybe a total list of what I really need. Where could I find such info? MY mid section and lower unite are in excellent condition.

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By the way, Tony is converting this engine from carbs to injection. I purchased a good complete injectionn system and Tony got it ready for me to have it installed on my engine after I figure wheere I am going with this.

[Hottrucks]

By the way, Tony is converting this engine from carbs to injection. I purchased a good complete injectionn system and Tony got it ready for me to have it installed on my engine after I figure wheere I am going with this.


Good call on waiting for the final verdict...your 150 will need a dif. tune than a 2.5 200...If your old motor runs good then a quick rering maybe all that its needed ( how many hours??) and you could do that yourself with some time and a GOOD MANUAL..also very in expencive..

Do the comp and leak down then let us know................

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Thanks again for all the help. I'll wait till I get the tests done. As far as hours?.....good question....used the boat a lot for the first 8 years fishing tournaments and club fishing...then divorce struck.....since then ...back to using the boat more for the past 2 or 3 years but no tourney's. Fishing with my friends and the new wife. Whew, what a great change. hahah

[basscat39]

Where in PA do you live?

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Next exit North of Allentown on the Pa Turnpike....Lehighton.

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Well guys, still haven't had the compression test done but thanks to scream and fly and a few people I purchased and learned how to do a leakdown tester. Did it last nite and this is what I have...Port side top to bottom 2%, 2% and 1% and starboard side top to bottom 8%, 5% and 5%. I don't know why one side would be so different than the other? Originally I was thinking about getting a 2.5L rebuilt powerhead to put on my mid with the Brucato svs and acu system and change the exhaust tuner to a Bob's. How much HP can be gained with my powerhead if I sent it to JSRE and still do the rest of what I was planning? I am a bass fisherman.

[T-REX]

That 91 2.4 iz call'd a "fatblock" kuz it iz in reality a sleeved down 2.5 block, so If U decide to go to a 2.5, it will be a simple 10bolt tune up!!

Wit your leekdown, U ain't lost 500 rpm bekause ov internal problems...U prolly got a lektrikle problem, or even a fuel induction problem(which Tony kan help U wit)...

If U are goin to efi, U kan pull 200+ HP outta that mota reel easy...Now, If ya gotta pay to have it cut, U may kum out better by finding a good used 200 2.5, and sell tha 2.4....U juss need to weigh tha odds, and see which path iz better fer ya!!

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Hi T-Rex
Electrical problem? Last May I had the stator, trigger and the 2 boxes replaced (the engine would not start once in a while, just cranking but nothing, so my mechanic narrowed it down to one of the parts I just mentioned. So I told him to replace it all.) What other electrical problem could I have checked? As for the injection conversion...you really think that with the stock 2.4L, Tony's stuff and the tuner exchange that I can get close to 200HP without doing anything else? I won't get it cut if I can achieve power like that with a stock 2.4L. If I do go with a good 2.5L powerhead and all the other stuff what HP could I expect then?

Thanks for listening and your help!!!

[T-REX]

U have 6 coils that kan break down, misfire, or juss quit all together, wiring harness, ground corrosion etc....Theyz a lot to tha electrikle part other than packs/stator/trigger...BUT, a bad ground or grounded wire or even broken wire kan cause any ov the other componants to go away!!...BAD GROUNDS ARE THA WORST ELECT KILLER!!....Even a bad battery connection...

Az fer tha 200 HP outta tha 2.4 wit efi....YES, It will all depend on tha fuel curve az how close to 200hp it git's...Wit 145#s ov compression, a PCU to adjust ya fuel curve, and XRI, U will be knock'in on 200hp's door...

2.5HP will soley depend on what 2.5 U wind up wit....they range from 150 to 300+....A 2.5 200HP left stock would be my pick!!

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OK ..... Sounds like a plan. Know of any 2.5L 200HP in great shape left stock???? Thanks

[Specialized P4-12]

i have 2 200 carb powerhead in excelent shape for sale in the engines section.... 3500 with covers and 2 piece exaust plase tuners and water tube..

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Well, the first phase of the project is done. Bought a rebuilt 200 powerhead from a member, thanks Glenn, and had it installed on my mid. Runs like a raped ape! Just hit the 10 hours mark and hammered the throttle a few times near the end. Next up is the swap from carbs to injection and the Brucato SVS and ACU. Looking forward to it.

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By the way, thanks to all who have offered advice so far. Great forum!