325 Monsoon performance mods

[OhTwoBu]

Hello Crew, Long-time lurker and first-time poster here. I'm the new owner of a 2002 23LSV, factory MLS, and stock 325 Monsoon. I've enjoyed it so far, but the boat does feel a little underpowered. It takes full grunt to pull skiers and boarders out of the water, and it tops out at around 38 at 4500 RPM. It has 350 hours on it. Before I try anything drastic, I believe a tune up is in order. I'm mechanically inclined and have no issues working on it. Where do you recommend sourcing the wear-out tune up parts: plugs, wires, cap and rotor, injectors? Signs also point to re-propping, and all I know is it has an OJ-4 blade. Specs unknown.

If it doesn't wake up after this, I'm willing to put in the time, effort, and money for hardware. I'm talking stroker kit, heads, etc. What are the factory heads on this engine and are they worth re-working? I'm basically asking what do I need to build my 325 into a Hammerhead or an LS1, or better? Cam? I also understand that the computer is a limiting factor on these engines, and there isn't much of an aftermarket for programming. If I decide to pull this engine and get serious, is there anyone out there who can program it to take advantage of the internals? Thanks to all in advance! Merry Christmas, Happy New Year, and winter projects!

[shawndoggy]

topping out at 38 and 4500 rpms sounds like a tune up is definitely in order unless you are running at 6000'?

[OhTwoBu]

Yessir, where do you recommend sourcing the consumables? I figured shopping for a 350 Chevy has to be endless possibilities. Just trying to avoid the dealer if possible. I live in the East SF Bay if anyone is familiar.

[shawndoggy]

bakesonline.com and skidim.com are both great resources.

[Nitrousbird]

Acme 2313 or 2315 should work nicely, along with plugs, cap and rotor.

Give up on the idea of motor mods. Most dream of it then see the cost and figure out it would be cheaper to sell their boat and upgrade to one with a better motor.

[dlb]

I have the same boat. With my prop I get over 45 mph and have no trouble with hole shot. I would start with plugs, wires and rotor. Check the prop. It will have numbers on it. Report that here and I am sure more help will come.

Did you have a compression check done as part of the deal?

[justgary]

As a joke, I was searching for a supercharger that you could cram under the hood when I found this. Seriously, I would figure out the 4500 RPM WOT thing before I started jacking with the engine. After that, the chip liar thing may be fair game!

Regards,

- Just Gary

[sgt1970-442]

how does the boat seem to run? how many hours are on it? I would for sure do plugs, cap rotor and wires. as mentioned check the prop, it might not have the right prop at all on it.

let us know after the tune up. fyi, if you have a real auto parts store in your area, they can come up with your parts.

lets see how this works before pulling the motor for a rebuild and computer re-flash

Edited December 24, 2013 by sgt1970-442

[OhTwoBu]

Thanks to all for the suggestions, I will post with the numbers I find on the prop and run a compression test when I get back to the states in three weeks (deployed at the moment). My primary reason for posting now was so I could buy parts and have everything in when I get back so I can go to work, and honestly just miss my boat and talking about it. I looked through bakesonline and skidim, both seem to have tons of parts but the organization by make, model, and year is hard to work through. If I were to walk into the local parts barn and ask for a dizzy cap, rotor, plugs, and wires for say…a 98 chevy 1500 with a 350…would I get what I need? I should probably grab a new fuel filter and PCV, any suggestions there?

[OhTwoBu]

Oh yeah, it starts fast and idles like a kitten. You can barely hear it running and would be tempted to hit the key again if you weren't paying attention. That brings me to a side note, tach doesn't work… The sending unit works because the perfect pass tach readout works, but no needle movement. 350 hours. It's just…a bit of a dog.

[sgt1970-442]

I believe the fuel filter is in the tank on your boat. I might be wrong on this but someone hopefully will chime in. yes if you take the cap, rotor, a plug, and wires your local parts store can match them up.

seeing how you mentioned the tach not working, are you sure the speedo is calibrated and reading properly? might want to make sure with a hand held gps.

[jb 156]

Acme 2313 or 2315 should work nicely, along with plugs, cap and rotor.

Give up on the idea of motor mods. Most dream of it then see the cost and figure out it would be cheaper to sell their boat and upgrade to one with a better motor.

This

[dlb]

That boat has an inline fuel filter, NAPA 3299. I have the best luck with the bolt on parts when I ask for 78 Camero with a 350, oil sending unit etc.

[Woodski]

@OhTwoBu: since you mentioned out of country, if you have internet access, you could hit some sites like Summitt / Jegs / DIM / Iboats / Wholesale Marine and order your parts online. It does sound like your boat is underperforming to it's potential. Tune up is in order, including all the filters (fuel) and a spark arrestor / air filter cleaning. In addition, I would check the engine alignment, prop shaft alignment and bearing condition (to make sure there is not excess friction in the system).

You should not need to upgrade the engine to get acceptable performance, just make sure it is running to proper specs. If you still have that need for more power, there are several things that are performance enhancers available to bump the power level up towards the 400 hp level - cam, heads, rockers, exhaust tweaks will improve the breathing of the SBC. Several members on the forum can proved guidance if you get to that point, and there are several posts on this site that document engine upgrades.

[justgary]

I bought a distributor cap from the local box stores and was surprised to get home and discover that it didn't fit. I had to use a hand grinder to remove a little of the flange at the corners where the fasteners are. Easy to do, and cheaper than going back to the store.

My boat has two fuel filters; one at the tank and another at the engine. Check your line at the tank and the engine to be sure you find all of them. While you are at the tank, make sure that the fuel cutoff valve isn't partly closed.

On a final note, I had to replace the fuel line on a riding mower because the alcohol had rotted the inside of the line. It had a chunk of itself lodged so that the engine would only idle. An extreme case, but it illustrates that the engine does not want any restriction in fuel flow.

- Just Gary

[Michigan boarder]

If you can have someone send you the engine serial # and maybe your hull #, that would likely help you. Also have them take some pictures of the engine, the distributor, etc. and send that to you. Then, with all that info in hand, pull up the Bakesonline website and call them at 866-993-BAKE. Odds are you will talk to someone that knows your boat well and will be very helpful. If you are unable to call, send them an email or PM them on this site (Bake's Marine is their member name) and they will get you set up with everything you need. Then at least you are good to go when you get back to the states. As you learn about your boat and have time to shop you can then decide who to buy from. I started out that way when I bought my Echelon a few years ago, and buy from a variety of sites now.

[Mika]

I also understand that the computer is a limiting factor on these engines, and there isn't much of an aftermarket for programming. If I decide to pull this engine and get serious, is there anyone out there who can program it to take advantage of the internals?

I agree, finding a programming tool that supports the (Indmar's?) ECM is probably the trickiest part. I've been tuning the LS1 in my Vette with EFI-Live programming tool and LC-1 wide-band lambda. After doing the homework it's no rocket science, e.g. getting the fuel map and ignition correct is a fairly straightforward task.

Another option in serious tuning would be replacing the ECM with some more common ECM from e.g. LS1 car. With this option you would have no difficulties in finding the programming tools but you would have to start more from scratch, the car ECM would require quite some modifications for marine use and I've got no experience of this.

If anyone of you know a proper programming tool for Indmars (not just diagnostic code reader/resetter, it should be capable to re-program ECM as well) let me know, I might be interested. And actually the same applies to a good diagnostic code reader: since there's no Malibu dealer in Finland I'd prefer being fairly independent and having a code reader of my own.

Merry Christmas and Happy New Year to all of you!

[justgary]

The main difference between a car engine and your marine engine is that the car runs closed loop with O2 sensors. The marine engine is open loop based on temperature, air flow, and RPM table lookups. You could modify some risers to add O2 sensors, even if only temporary to give you readings while you tune the open loop system.

Just Gary

[Mika]

The main difference between a car engine and your marine engine is that the car runs closed loop with O2 sensors. The marine engine is open loop based on temperature, air flow, and RPM table lookups. You could modify some risers to add O2 sensors, even if only temporary to give you readings while you tune the open loop system.

Just Gary

Do you know if that's the case with the newer Malibus also? In 2009 Monsoon (closed cooling) there're both O2 sensors and lambda sensors in the risers. Do these engines run closed loop?

[justgary]

I don't know, but I can't think of why they would have sensors in the exhaust stream for any other reason than to run closed loop. Call Indmar and ask sometime.

[greg2vlx]

OhTwoBu,

I just got back from my extended vacation in the sand a little over a week ago and did manage to get on the water last week for a quick ride. It's always nice to get home and get on the water. Hope you have a safe trip home.

Greg

[OhTwoBu]

Greg,

Thanks man, and welcome home!

Has anyone ever sent their ECUs out to a third party for reprogramming after tuning their engine, similar to how old OBD I vehicles had to be worked on? Or lets say, stroke their 350 to a 383 and then source a hammerhead ECU? Plug and play?

[shawndoggy]

as nitrousbird suggests, going down that road doesn't make economic sense. You spend a bunch of $$$, and then have something "weird" that no mechanic will be able to work on. OK, not "no mechanic," but only a sophisticated one (i.e. not the typical boat dealer tech).

but if you want to go down that road, check this out, then report back: http://www.mefiburn.com/

[Andrew63]

Have the 350 monsoon in a 2011 RLXI with catalytic converters.

4 x 02 sensors, 1 pre & 1 post CAT, so it must be a closed system.

Having similar performance issues, well issues to me.

Running the stock 3 blade acme 13x11.5" prop with engine rpm 50-100 rpm below the min operating range

4500-4550 rpm at 41.5 mph

Removed & cleaned the cats, no difference.

Removed the cats completely, no difference.

Put new plugs in, no difference.

Checked fuel pressure, this was fine.

Took it to a dealer thinking the computer may be holding back the engine or timing out as I had no way to check this area.

All checked out fine.

Changed to a new acme 3 blade 13x12" prop, slight improvements. Now I am running 4650-4700 rpm at 43mph.

Could not figure out if below the rpm range how a larger pitch prop would help.

Some crew members suggested the original prop may be operating past it's best efficiency.

What I did find is the original prop hade been repaired, generating a slight vibration at wot but also the cup was more pronounced on the old repaired prop compared with the new prop.

Boat runs smoother at 30 mph and above with the slight vibration gone.

Still believe I should be getting more out of the engine.

Will be interested in your findings

[Nitrousbird]

Have the 350 monsoon in a 2011 RLXI with catalytic converters.

4 x 02 sensors, 1 pre & 1 post CAT, so it must be a closed system.

Having similar performance issues, well issues to me.

Running the stock 3 blade acme 13x11.5" prop with engine rpm 50-100 rpm below the min operating range

4500-4550 rpm at 41.5 mph

Removed & cleaned the cats, no difference.

Removed the cats completely, no difference.

Put new plugs in, no difference.

Checked fuel pressure, this was fine.

Took it to a dealer thinking the computer may be holding back the engine or timing out as I had no way to check this area.

All checked out fine.

Changed to a new acme 3 blade 13x12" prop, slight improvements. Now I am running 4650-4700 rpm at 43mph.

Could not figure out if below the rpm range how a larger pitch prop would help.

Some crew members suggested the original prop may be operating past it's best efficiency.

What I did find is the original prop hade been repaired, generating a slight vibration at wot but also the cup was more pronounced on the old repaired prop compared with the new prop.

Boat runs smoother at 30 mph and above with the slight vibration gone.

Still believe I should be getting more out of the engine.

Will be interested in your findings

That still seems like a low RPM and top speed for a Monsoon powered DD.