motor issues? max rpm not even close

[QC]

Re: motor issues? max rpm not even close

50 at 4000 would be 5% slip which is almost impossible so I don't believe it, definitely not into the 50s if the tach is right. Do you recall the RPM right at 40? Need to confirm the tach before you do anything else and the speed numbers. Maybe a switch on the back for 4, 6 or 8 cyl . . .

With a screenname like garmin0204 you have to have a GPS. Right? No?

 

[garmin0204]

Re: motor issues? max rpm not even close

i dont own a gps anymore i sold it with my fishing boat, well believe what you want i am just going by what his spedometer said when we were both in the water, he was maxed at 40mph and i passed him and pulled away easy he has a 25ft center console with a 225 yamaha outboard, i am working on borrowing a gps for the weekend so i can get a definate speed on it and yes the tach is right it is a brand new autometer nexus series tach and it is on 8cyl, and i even double checked the tach today in my mustang so its definatly good..

 

[QC]

Re: motor issues? max rpm not even close

Super light race boats would beg for 5% slip, so that's why I ask. I would believe 47, but either the pitch or the gear ratio are wrong if she actually ran 50. It's a math thing . . .

 

[garmin0204]

Re: motor issues? max rpm not even close

i was just goin buy what he said and how i was pulling away, so i am gonna borrow my buddys gps this weekend and see how fast by gps.. i am not doubting what you say at all as i am new to this, so after reading all the stuff here maybe just a prop change? what do you think ? and is the line off the mech. fuel pump just a vent tube? where does it go?

 

[TilliamWe]

Re: motor issues? max rpm not even close

The line off the mechanical fuel pump goes to the front of the carburetor. It's there, so that if the internal diaphram of the pump fails, instead of fuel leaking into the bilge, it goes into your motor. So, if you have fuel in that line, your fuel pump is junk.

 

[garmin0204]

Re: motor issues? max rpm not even close

ok here is an update on my problem...

went out with gps boat was running 46.8mph gps was acurate within 3ft so it should be an acurate speed i just switched to a holley electric marine fuel pump and reg. (its the blue pump) set my fuel pressure at 5psi recomended by edelbrock for there carb, it runs like a champ and jumps up on plain quick but it hits 4000 rpm and its like i hit a wall i tried raising the timing and it didnt do anything at all... so i put it back to 12deg initial and advancing 21deg all by 2800rpm so 33deg total timing, rockers are adjusted perfect plugs are good and read good after a WOT pass down the creek, so i guess now i should look into a prop change either to a 19 or 17 pitch to bring up the rpms? thats all i can think of anything else for me to check? thanks for all your help guys so far with my project

 

[weekend warrior]

Re: motor issues? max rpm not even close

I just wanted to share an issue i had recently. Boat ran fine for days and suddenly would not go more than 2800 rpm. its a 454 mercruiser

I went through everything like fuel filter, carb, fuel pump, vent lines etc.

Turns out i had a damaged plug wire. Once i replaced it, bingo, i was back to running at spec. I never would have looked there if a young boy in the marina didnt suggest it. Turns out that his outboard had the exact same problem the day before.

I know very little, but if my experience helps you, right on!

 

[rbh]

Re: motor issues? max rpm not even close

how much do you trim the leg up on plane?
rob

 

[222elite]

Re: motor issues? max rpm not even close

I'm running basicly the same engine as you are but with chevy vortec heads and GM hot cam. 1987 Wellcraft 222 Elite is a larger and heavier boat. It has a 20 pitch SS prop and running 53.3 @ 5400 rpms. on GPS. Are you sure your stringers and floor aren't full of water.

 

[garmin0204]

Re: motor issues? max rpm not even close

nope no water i had the center section of my floor out checkin my fuel tank and no water everything was dry it was out of the water from oct 2008 to june 2009 while i was building the motor and i keep it on a trailor not in the water also ... i guess i will try the plug wires next i have a set of MSD custom fit wires just havent felt like cutting and fitting them yet.. i guess that will be my next project thanks for the tips guys

 

[QC]

Re: motor issues? max rpm not even close

went out with gps boat was running 46.8mph gps

I would believe 47

Yeah, so the math seems to be working now . . .

The ultimate question is whether getting your RPM up with a prop change would get you some more speed, or if you have an actual engine performance problem. I suggest you take a peek at the Adults Only section, I believe item #12 is for low WOT RPM. Eliminate those items that don't apply, check those that do. If everything is right (even including the plug wires, timing, compression etc. etc.), then you need to start playing with props. If something is wrong, fix it and then retest with the existing prop. Get data, make subsequent prop change if necessary.

 

[garmin0204]

Re: motor issues? max rpm not even close

well guys i found my problem i replaced my wires with the MSD wires and it ran alittle better got up to about 4500rpm then i was reading my msd ignition books for any info and i found my plugs with the msd ignition were supposed to be gapped at .060 with under 10:1 comp. the were @.040 so i changed the gap to .060 and guess what it runs its butt off now runs all the way up to 6000 rpm and pulls nice who would have thought a plug gap like that would be such an issue thanks to everyone who helped me out, now its time to sell the boat