baja 342 mag 502s help
 

my baja 342 has a pair of 502s spinning bravo 1 4 blade 28pitch props im only getting 3900rpm somethings not right,manual says 5200 with these props ,any suggestions please!!!!!!!!!!!!!!!also top speed is 64mph

Re: baja 342 mag 502s help
 

Are they EFIs? Could they be running in "safe" mode for some reason?
Have those props always been on the boat?

You've got a very low prop slip # (7%). Maybe you simply have to go down a size in prop pitch.

Re: baja 342 mag 502s help
 

64 mph at 3900 is optimistic. Is this speed via the speedometer or GPS? If it's by speedo, you're top speed is probably more like the high 50's...

I'd say you're over-propped. I'm running 26's on my 342 with 496 HO's and am thinking about having the 26's labbed as my max rpm is around 4800. I think it's just too much weight for those engines with 28's.

Re: baja 342 mag 502s help
 

Your props must have come with the boat? There is no way a pair of stock 502's (if they are) are going to spin a set of 28 pitch props to the correct rpm in a Baja 342. Your only problem is your overpropped. Try a pair of matching 24's but don't buy props until you have tried a few sets. Your boat should probably run 66-72 with those motors at just over 5000 rpm's depending on load. Its easy to really load these big boats down too if you get 4 people on board and a full tk of gas plus gear,Smitty

Re: baja 342 mag 502s help
 

cheers guys many thanks they are efis props were with the boat when i bought it last year only just started using it after having had a lot of repair work done on the motors the guy i bought the boat from is not sure if there original with the boat,speed check was the boat speedo so none to accurate,most tests have been with half tank of fuel and just me and wife,no gear on board,so ill try a pair of 24s first see what that does,can i find out from baja what it came with new?
c beastwood whats your fuel consumption with the 496 motors, mine are the stock 502s, new manifolds and risers and one head skimmed and valves redone on one engine, id love to try and sort this boat out it sounds great but doesnt go that great , thanks guys!

Re: baja 342 mag 502s help
 

My fuel consumption is normal for a twin-engined big boat (i.e. - terrible).

If you go to www.boattest.com and search for the 342 under Baja, their test boat ran 70.1 mph at 5,000 rpms. GPH at that rpm was 66.4. It says that this was achieved with 14 x 28 props but I find that hard to believe unless the test was done in a virtually empty boat in salt water with a good wind at their back...I've hit 70 in the open ocean in similar conditions ONCE...

Re: baja 342 mag 502s help
 

cbeastwood many thanks for that id love mine to come near the 70 mark,im going to try smaller props but im so low on revs at 3900 rpm, there a great boat, a little rattly ie things work loose when it gets choppy, but it looks so sexy is yours a hard screen or glass?

Re: baja 342 mag 502s help
 

If this test is what someone based the props on this boat from (its possible) the big difference is they are saying 14" dia by 28 pitch,that would have been some kind of cut down prop which would have rpm'd higher,a typical bravo 4 blade is 15 1/4 dia so maybe thats were things got so far off,just caught that re-reading the post,Smitty

Re: baja 342 mag 502s help
 

Smitty,

Interesting observation - I had no idea that these were smaller diameter props than normal. 1 1/4" sounds like quite a bit of diameter to remove but it sounds like it really worked for that boat. So well in fact that I may look for a set to replace my 15 x 26's...

Anotherdimension, I don't think that these boats are more rattly than any other that are so full of options - microwave, refrig, full windshield, etc. - there's a lot to bang around so I guess I just expect it a little bit. Mine doesn't really rattle that much though. Just the cabin door really...Here are a few pics of mine...post some of yours!

Re: baja 342 mag 502s help
 

what gear ratio, if it has 165s like some of the newer stuff poss could came with 28s, but my 29 came with 23s :eek:

Re: baja 342 mag 502s help
 

I have a 342 with 502s and my top speed with 6 people and full fuel is about 64-65 on GPS. I am spinning 26s at about 5K. My boat is pretty heavy with the generator, a/c etc. I was going to play with the props and other stuff but you know what, 65 is fast enough for me. I love the boat and normally cruise about 40 and 3-3500 rpms. It is amazing that at 3500 you get good fuel consumption. When I take the motors to the firewall you can almost watch the fuel gauge drop.

Re: baja 342 mag 502s help
 

c beastwood great pics yours looks in great shape,ive got the hard screen version,they are a great boat my main rattles are from the sink unit going to take it out this winter and refix it,i will try and post some pics later ill dig em out.
jonnyboatman ill check my ratio
duksrule, thats cool must admit we spend most of our time in the boat at 3500 rpm i found fuel consumption is best there,agree full throttle my gauge goes down ,interesting your getting only 65mph,mine as no genirator or air con, so is fairly light,tried mine with low fuel and just me only 3900 rpm and about 63 mph just want it to hit 70 every now and again
for the fun of it!!!!!!

Re: baja 342 mag 502s help
 

A friend of mine has a 342 withthe same options and the same results as you. I also believe that he is spinning his 26" props in.

Re: baja 342 mag 502s help
 

3900 us way to low. You should be hitting 4800+ on those motors. Props are also a good place to start. You may want to get a scan tool and check to see if they are running OK. If they start to knock the computer should retard the timing and that may be what is keeping it down to 3900. By no means am I an expert though.

Fastes I have ever had mine was 68 GPS and that was with just me, 1/4 of fuel. I must be one of the few on here that isn't chasing that extra few miles per hour. I just love my boat and am perfectly happy with it the way it is. Here is a pic of mine.

Re: baja 342 mag 502s help
 

duksrule and anyone else,nice pic duksrule my camera is down at the moment and none stored on my pc will be back in 2 weeks with my pics,
just at my boat and checked ive messed up there 26inch bravos, so its not the props ,could it be the timing whats the scan tool?
cant believe ive mucked up and there 26s help please!!!!

Re: baja 342 mag 502s help
 

That boat should run 65mph with 26" Bravo props at 4900-5000rpms.

From all you've posted, your top speed is 64mph. I'm guessing that your tachs are off. No way you are going 64mph at 3900rpms.

Re: baja 342 mag 502s help
 

griff to be honest my reading of the speed was from the boats speedo which i believe is none to accurate next run out im borrowing a gps, from past boats it does kind of feel low 60s others seem to think it should be top 60s with these motors,both rev gauges do hit the same rpm though one a fraction higher than the other , ive got two weeks of next week which im spending on the boat so i want to get it right myself,could it be the timing, how do you set it up on the 502, at idle?

Re: baja 342 mag 502s help
 

ok ive been boating!,redid the timing on both and while in the engine bay did a few checks and by chance took of the remote oil filler pipes instead of just checking the oil on the stick and removing the top cap and filling, and oh no mayonase everywhere oil mixed with water yuck what a mess and this is on my port side motor where ive had work done!so i strip the top out and find the problem to be corrosion on the inlet manifold on the blank of sections at the back end of the engine so i do a quick repair on it with epoxy instant metal file it all down clean and fit new gaskets , flush the engine through with diesel and oil ,change the oil 3 times to remove the mayonase,change the plugs and all sounds great take out for a run my good engine now pulls 4500 rpm and my repaired one does abot 4250rpm ,so the question is have i done permanant damage to the engine , is it worht a rebuild or a new motor?

Re: baja 342 mag 502s help
 

I AGREE CHECK THE TACHS NO WAY THAT YOU ARE GOING THAT FAST AT 3900RPM

Re: baja 342 mag 502s help
 

by u boy things have moved on read the above post

Re: baja 342 mag 502s help
 

Possibly you have a little more blowby on one engine than the other. a compression test will tell you.

Re: baja 342 mag 502s help
 

SORRY I POSTED BEFORE I READ THAT.

Re: baja 342 mag 502s help
 

by u boy no worries ,getting desperate here!
payton the engine thats gotthe inlet manifold pressure was low on compression in one cylinder ,had the top stripped on that one it had dropped a valve ,the mechanics re ground the valves skimmed the heads and re fixed it , said it was all now good on compression , now ive got trouble with the inlet manifold, done a temp repair on it for now, it runs ok but still not pulling the revs of the other motor, just wonder if ive done permanant damage now to this motor, with water going in etc , cant understand why they didnt see the inlet manifold when they stripped it down in the winter!