Mercruiser 260 help
 

Hey guys,
I'm new here, but have been reading for some time now. It seems like a bunch of good knowledgable people here. I have a couple of questions so I'll start with an overview of my situation/problem. I have an 86 Wellcraft Nova it has the 260hp 350 in it. Last year i had a real hard time starting it when it was cold. Over the winter I installed a new intake(Eldelbrock performer) and a new carb. (also an Eldelbrock). I went a little too big on the carb as I intsalled a 750cfm. When I got it out at the beggining of the season I was pleased as it fired right up the first crank. But as I started running it down the lake it ran like crap. I went through and put a new pump and fuel pressue gage. I also went through the ignition system with a new coil, pickup, plugs, wires, and cap and rotor. All of these helped with the boat except the top end. I lost 400 Rpm here. I put the old carb back on it thinking that the new one was too big; same thing. I realized the timing was way off and the initial timing to 10BTDC. It was the same. I had it looked at and was told the thunderbolt ignition was causing an irratic spark. that was replaced and still nothing has happened. One time it did hit the RPM it did last year. but the next WOT run i did nothing. anyone have a clue? OK last question, the boat has 880hrs on it. I am going to repower it after next season. I will be upgrading instead of just replacing. How much torque does the 260 put out. I would like to have an engine that would get this heavy boat up and running quicker without destroying my outdrive. Thanks in advance
Ohmthis

Re: Mercruiser 260 help
 

Question I may tro to find out myself sometime soon on the dyno. Anyway, I think a fair guess would be around 310-330ft/lbs since the 250hp GM 4bbl engine puts out an advertised 305ft/lbs.

For such a low compression, puny camshafted engine - yes, that carb is "too big" but most importantly, fuel calibrated incorrectly for your motor. It is calibrated as a universal bolt on for mild 454's .

People have called BS on me (those who don't know me) but I have gained close to 5mph on my little '90 2800lb boat with Bowtie cast iron intake, BG650, and 'tune tweaking'. 260hp Mag STOCK Long block has a quazzilion overrev hrs on it and is due for a refresh.

Every boat is different, so what effect a certain amt of power has one means nothing to another one.

BTW: I feel with good driving a 380-400ft/lb or small block will be fine in frt of the Alpha. If you are not using them, a set of trim tabs will make the boat trim much easier with much less power at takeoff. Do not overprop either. This will help the drive tremendously !

Re: Mercruiser 260 help
 

I have a 93 nova it came with a 330hp 454 and a bravo drive. it ran 62 stock. I would at least do a 383 and do it all exhaust ign everything heads balancing etc. if not go for a big block

Re: Mercruiser 260 help
 

Do you have through hull exhaust? If not, get some, it helps a ton. If you do already, get a good exhaust system (Stainless Marine) And at 880 hrs you might want to throw a can of Maverel Mystery Oil in it

Re: Mercruiser 260 help
 

I had the same issue..when I did a intake...I even called Dennis moore ..I think it was the secondary metering rods...?? who knows they are not like a car engine....but yet they are???

Re: Mercruiser 260 help
 

Thanks everybody,
I already had the notion to graduate to a 383 when the repowering will be done. I probably won't go for a brand new ignition system as everything except the dist. is new this year. Also I don't have thru hull exhaust, but that will be put in for next year. As far as going hog wild on the engine I would almost rather take that money and get a new boat. I mean hell, the boat is 20 yrs old. I replaced the out drive on it last year and if I upgrade the engine I might be looking at putting what I paid for the boat back into it. I was thinking of a crate engine, but all you see is HP ratings nothing of the tq. I've been looking and I have found some 350/325 hp. I would like to have about 350-400hp and about 400tq. Anyone see anything out there for around $3500-4000? I'm not trying to be cheap, but I can't justify having more in the engine and drive than the boat is worth. Thanks!
Anthony

Re: Mercruiser 260 help
 

Heres a couple options for you but most good marine engine builders/machine shops could build you the same if not better cheaper.
http://www.jegs.com/webapp/wcs/store...tegoryId=10763

http://www.jegs.com/webapp/wcs/store...tegoryId=10763

Re: Mercruiser 260 help
 

Thanks Dave,
That was exactly what i was looking for. Now back to the original question; can anyone help me find those missing 400 RPM? I am running the original carb with all the new ignition parts, along with the new intake. I would like to have this figured out before I delve into the new engine. If it is something that will affect the new power I just have to fix that now. Thanks again everyone! BTW, I just might see some of you guys at the Lake Cumberland Poker Run. Have a great holiday weekend If I can't respond before I leave!
Anthony

Re: Mercruiser 260 help
 

First question:
Have you done a compression test?
Second question:
Have you done a leakdown test?

It could be that the engine is just tired...
Kent

Re: Mercruiser 260 help
 

And all those hp ratings are lies and trickery to get you to buy a truck block ( called marine) . Been there done that. Merc long block would be better @ like 3g with a 2 year warranty. how can you beat that? It runs right the first time! :rolleyes: