Super Noob, Help Im trying! WOT? rpm?

[sakrafice]

Well to make a long story short i bought a boat, had to rebuild the motor. Anyway I finally got it out on the water the otherday and for first day out on the lake "have had it running on hose for testing ect..) She ran damn good I thought... Well i know i need to adjust my carb a little better and maybe adjust timing more but i figured id check here first.. since maybe it might be as simple as adjusting the throttle linkage. I have a 97 Sylvan v196 bowrider with an alpha one gen 2 outdrive. I think its a 19 pitch. It orginally came with a 305 / 2bbl , points ect... well i converted it to a 350 / 4barrel, electronic ignition, electronic fuel pump that says "regulated from i think 6-8psi?, not at home to look, mr.gasket makes it) And to get to the point when i go WOT i get to about 4500rpm , now maybe thats because i have it timmed all the way down since i had a problem with trim cylinder and couldnt plane out or what i dont know? is it my prop? i dont think so, boat has plenty of power and pulls extremely hard on this new setup. i should be able to rev out to about 6k if i wanted to so im asking what should i be looking for to solve this issue? at 4500 rpm i was reaching only 45mph. Boat is 19.5ft, im trying to reach high 50's and i do know ill need a better prop for that but at this point i need to get the rpm to work right before i continue any further. ANY help is appreciated, i just got into boating, didnt have alot of money so i do this as a project over the winter and up until the other day when she first got to see water again. so please go easy on me. thanks!

 

[45Auto]

Re: Super Noob, Help Im trying! WOT? rpm?

When you did the conversion to the 350, did you use marine or automotive carb, ignition, etc? Where do your carb overflow tubes dump? Does your distributor have a vacuum advance? What kind of cam are you running that makes it worth spinning to 6K RPM? A typical marine cam makes mid range power, the power curve tends to drop rather quickly after 5k RPM.

Your trim being all the way down will have a HUGE affect on top speed and WOT RPM. Not much point in messing with anything else till you fix that.

EDIT: Just saw your previous post about the Weber and Thunderbolt ignition. You still need to get your trim working before worrying about props, etc.

 

[sakrafice]

Re: Super Noob, Help Im trying! WOT? rpm?

okay. Im sorry im just now learning all this stuff and dont know all about triming and plane and stuff yet, i am a quick learner but its something i need to feel to learn so to speak. Im fixing the cylinder saturday when i go pick up a new one. I will definetly be back on to let you know what has happened. Thanks buddy!

 

[smitty28]

Re: Super Noob, Help Im trying! WOT? rpm?

I dont know exactly what you got but a merc 350 spins 4400-4800 WOT....looks like your spot on. Get the trim fixed and youll probably pick up the mph's youre lookin for....pretty sure 6k would smoke the motor real quick

 

[sakrafice]

Re: Super Noob, Help Im trying! WOT? rpm?

I was just going by my friends boat which has a 5.7/ 350 on it although it (55mph) has a volvo drive and can take it to 6k... perhaps thats the diffrence...? and the fact that his fourwinns weighs 5k something pounds to my 2800... maybe someone else can confirm that about 5k is about it for me. Looks like 60mph is going to be out of reach for me which is an upset seeing that my friends 4.3 bayliner does 55 and is a v6, guess i wasted my time putting a bigger motor and intake/carb and updating the boat a bit. Only other thing is it may have bad gas as boat hasnt ran in about 6years i just dumped in so isoheat, some seafoam, and lucas octane booster and added 10 gallons of 93 but im sure it still just needs to be drained out or ran through to get its full potential. I know people will state that if i wanted speed i should of boat a diffrent boat yada yada but perhaps i can get it close to the speed i want without sacraficing all my low end since i mostly cruise around and tube but is fun to get into a few races with the friends out there (safely of course)

 

[NHGuy]

Re: Super Noob, Help Im trying! WOT? rpm?

After you have the trim fixed and the old fuel purged go run it to 4800 rpm with the trim raised enough to get your max speed at that RPM. Then post your results in the prop forum. There's tons of help there.
This will make you feel better. I bought my boat with a 19 pitch prop. Then got the engine running better. My boat is an 89 with the pre vortec heads and it runs to 58 MPH with a new 23 pitch Michigan Wheel 3 blade Vortex prop. (On a scratched up lower unit-which will cause some drag) To get there I took it to 4950 RPM, it was still accelerating well but I backed off because of the recommended RPMs of 4200 to 4800.
No sense for me to get a taller prop because my boat spends almost all of it's time at a 45 MPH lake.
But you have a good shot at 60 in your boat. Just work through the kinks, and learn how it handles at higher speeds. When you are over 50 MPH things are different in little boats like we have.

 

[sakrafice]

Re: Super Noob, Help Im trying! WOT? rpm?

Thats what my buddy told me to put on my boat before it even got it running was a 23 pitch, but like everyone has mentioned i must fix my trim first and get all the little bugs worked out before i really work on speed. I just figured having a bigger engine on the boat would help me with torq which would allow me to run a better pitch prop and still keep some low end power. Its a GM reman motor that was bored 60 over according to the stamp they put on the motor. I had to rebuild the engine do to there lack to put a oil sump incorrectly and it was laying on bottom of my pan so i used a hi volume pump, idle's over 40, WOT 80ish, but thats the guage im going to hook up a mechanical to find true pressure. Also has a marine oil pan but the pan is overkill for the unit but i figure the more oil the better when running at high rpm all the time along with longer oil filter. I know this dont mean much but I did build it to last. Carb is supposed to be edlebrock/webber 4barrel and i even put spacer in to add a few more hp. One thing i was reading online and something i seem to here is after the second time i gave her WOT for about 45seconds i could here a noise as if i had a vacumm leak or something, and aacording to people with that symtoms is that the secondaries are opening to early or something which is what got me all worried. Im just going to fix trim, and take it back out and actually do some testing, when i took her out the other day it was more or less to make sure she would float and stay running, and to make sure everything was okay before i go putting the interior back into it since if there was a problem id hate to have to take it all back out to work on engine!

 

[haulnazz15]

Re: Super Noob, Help Im trying! WOT? rpm?

First off, I seriously doubt your friend's Bayliner does 55mph on a 4.3L unless it's a 16ft boat. Use a GPS next time you go out and I bet you find out he's in the mid-40's. Your boat should be topping out around 44-4600 rpms or so, it doesn't appear that anything is wrong except your trim issue. That will give you another 3-5 mph I bet, butyou're not likely going to get high 50's out of a 5.7L without 300+HP.

 

[HT32BSX115]

Re: Super Noob, Help Im trying! WOT? rpm?

it runs to 58 MPH with a new 23 pitch Michigan Wheel 3 blade Vortex prop. (On a scratched up lower unit-which will cause some drag) To get there I took it to 4950 RPM, it was still accelerating well but I backed off because of the recommended RPMs of 4200 to 4800.
No sense for me to get a taller prop because my boat spends almost all of it's time at a 45 MPH lake.

You're "under-propped" and really should either put a "taller 3 blade prop on it or put a 4 blade (of maybe the same pitch or 1" either way) on it.

It shouldn't turn more than the upper limit at WOT regardless of how fast it's going That's why Mercruiser has a range of WOT RPM.


You usually want to prop for at or close to the upper RPM limit with the boat loaded (fuel/people/gear/etc) where you'll run it most at the elevation where you boat most.....

WOT for about 45seconds i could here a noise as if i had a vacumm leak or something, and aacording to people with that symtoms is that the secondaries are opening to early or something which is what got me all worried.

It's probably not a vacuum leak. There's little or no vacuum at WOT.....


If you're making a LOT more HP and a fairly tall prop won't keep you within the max RPM range......you might have to get a higher ratio drive. You can only turn certain (regular) props so fast.....turn them too fast and they cavitate, ventilate etc.....


Is yours a 1.5:1 drive ratio? If so it shouldn't be a problem..... it might be good up to 5500 RPM or so. (there's probably people turning them a lot faster......Like a certain Dr Of Chemistry I know!!)

The "rule of thumb" propping for MAX RPM still applies. If you rebuilt your engine and you balanced it, etc ....... 5000 RPM should be no problem at all.....

 

[haulnazz15]

Re: Super Noob, Help Im trying! WOT? rpm?

^Agreed. The RPM range isn't set because of the engine's limit, it's the outdrive's limit.

 

[rickryder]

Re: Super Noob, Help Im trying! WOT? rpm?

I have the 5.7 4bbl Merc in a Four Winns 210 and get 42MPH on gps @ 4500rpm..... My boat weighs in at 2080# without the motor and drive....with everything in the boat I don't think it's over 4000#

 

[sakrafice]

Re: Super Noob, Help Im trying! WOT? rpm?

You're "under-propped" and really should either put a "taller 3 blade prop on it or put a 4 blade (of maybe the same pitch or 1" either way) on it.


Is yours a 1.5:1 drive ratio? If so it shouldn't be a problem..... it might be good up to 5500 RPM or so. (there's probably people turning them a lot faster......Like a certain Dr Of Chemistry I know!!)

The "rule of thumb" propping for MAX RPM still applies. If you rebuilt your engine and you balanced it, etc ....... 5000 RPM should be no problem at all.....

Motor is a fresh rebuild straight from gm. ill see about uploading a pic of the stamp and all. It was balanced ect. How do i find the ratio of my drive? I know forsure its a Alpha One Gen 2, assumuming it came with the boat/original set up for the 305. My boat is a 97 if that helps at all.


As for the guy saying he doubts the 4.3, its an 07 bayliner and was on gps at 54mph with 3 people on. I hade 3 people only on mine and got what ive explanied above. My motor factory rated is 260, now i know boring dont help much but it is some. so gives me a little more, now add 4barrel intake and 4barrel aftermarket carb with spacer i think im around 300 or over. Only other little thing added to the boat is the shark fin on drive... the damn boat dont even have interior in the back thats going to add even more weight. there is no way in hell the power i have i should be only doing 40 with a few people on it. Sorry im not trying to be rude but ive seen my friends fourwinns with high gun walls 5k pounds doing 55 on gps with a 23pitch and 7 people on it. His boat is rated for 10 people mine is 8 people max. I kinda think it is either prop or ratio but i need to really figure this out, i dont understand all this prop vs hp stuff yet. Maybe i wired the boat up wrong because i had to build my own harness... this has been a chaotic mess. But in the end the boat still had a great first day ever on the lake since ive owned it by doing 45mph apparently at around 4500 rpm with trim all the way down. Thanks all for replies and keep them coming beleive it or not im learning from them.

 

[haulnazz15]

Re: Super Noob, Help Im trying! WOT? rpm?

The thing is, your motor is rated for 260HP WITH a 4bbl carb and manifold, the carb spacer is good for maybe 10HP. It just takes a lot of HP to go from mid-40's to mid-50's. I would suggest you get it re-propped so that your rpms top out at 4800 or so. I made the comment about the Bayliner because if he also has a 20' boat like you, the 4.3L is only a 220HP or so engine and won't likely get that fast. The only reason the Bayliner will achieve higher speeds is because they are very light due to lack of quality materials.

 

[sakrafice]

Re: Super Noob, Help Im trying! WOT? rpm?

It was rated at 260 on 2barrel carb/mani. When i got the motor i replaced. Id have to get some pics, but it shows rating on the valve cover, and the rebuild specs on portside or motor near oilpan on block.

 

[haulnazz15]

Re: Super Noob, Help Im trying! WOT? rpm?

It was rated at 260 on 2barrel carb/mani. When i got the motor i replaced. Id have to get some pics, but it shows rating on the valve cover, and the rebuild specs on portside or motor near oilpan on block.

Sorry, I just noticed you have a '97. The older 5.7L's were rated at 260HP with the 4V carb.

 

[sakrafice]

Re: Super Noob, Help Im trying! WOT? rpm?

Its okay buddy! I just want to get my boat moving a little better!

 

[sakrafice]

Re: Super Noob, Help Im trying! WOT? rpm?

UPDATE

Trim Cylinder fixed. Took it out boat ran worse then before, was spiting and sputuring.. had 5 people on it with interior in (back) It would do at best 32mph at 3k rpm... Weight shouldnt be in issure on how fast the motor is turning.. Decided to just enjoy the boat for the night so i did and took it out the following day to test and tune after replacing the fuel filter/seperator.

So took it out and took some people that know alot about engines ( not boats =\ ) started by advancing my timing but had to back it down a little bit but did get me to 4200 rpm before it started backing firing. Then they noticed that my electronic fuel pump was not in correct place, by this i had it sucking instead of pushing and had put it after the fuel/water seperator which would make good sense why it was starving sometimes persay. Havent swaped its place because we where currently out on the lake. Then found that there was slack in my accelorator cable that was robbing some rpm, then found out my secondaries where not opening! They got them open and the boat finally came alive! It still needs some stuff done to it but im at 5k rpm and hit 50 with 4 good size guys on it with the 19 pitch. Once i swap that pump around ill be able or should be able to stay at WOT without the sudden pause in power for it straving for fuel...

A question I have is, is there a diffrence between a automotive coil and a merc coil? i swapped to a automotive because the merc one looked pretty nasty. They want me to put a hi performance distrubutor in it to give it more spark and to just use a race ignition one and not a marine if there really is much of a diffrence..

So ill be taking it out tonight or tomorrow with the other things finished up and borrowing my friends 23pitch 14 in dia... let me know what u guys think about 5k rpm being max for me? and or if getting a better set up on my distrubutor. thanks!

 

[HT32BSX115]

Re: Super Noob, Help Im trying! WOT? rpm?

Weight shouldnt be in issure on how fast the motor is turning..

It ABSOLUTELY IS A FACTOR! An over weight boat will NOT even plane in some cases. try tethering the boat some time to a dock or the beach etc....... and see how much WOT RPM you get with the boat not moving (static RPM) at all....... It might not even make it to 3000 RPM!

Then they noticed that my electronic fuel pump was not in correct place, by this i had it sucking instead of pushing and had put it after the fuel/water seperator which would make good sense why it was starving sometimes persay.

I am going to have to look closer but I think standard practice is to put the fuel pump (electric or otherwise) AFTER the fuel filter/separator. The reason is that if the filter is loose or leaks, having the pump AFTER the filter
1. puts filtered fuel through it
2. prevents leaks (BOOM!) in the engine compartment if the filter gasket leaks because it's loose or becomes loose.

They want me to put a hi performance distrubutor in it to give it more spark and to just use a race ignition one and not a marine if there really is much of a diffrence..

Don't know what you mean by "RACE not a marine" You MUST use an SAE J1171 USCG approved dist or you will not be in compliance with USCG regs.

 

[sakrafice]

Re: Super Noob, Help Im trying! WOT? rpm?

Well im going to swap it anyway to see if it takes care of my problem(fuel pump).. I may also look into the correct protocol on how its supposed to be installed, Maybe the pump is just not a good one as it was from mr.gasket.. As for the distributor I mean a distributor that is high performance instead of a generic marine. I do know they make marine hi performance ones as well, was just asking is there really a difference other then the safe guards it supposedly has. And does anyone know max rpm as I have seen 350's going up to 6k fine. Thanks.

 

[haulnazz15]

Re: Super Noob, Help Im trying! WOT? rpm?

You're asking for trouble on the fuel pump. You don't need high-performance ignition components, the points/coil you have will handle anything that 350 will do in a marine application. Max rpm limit is a limitation of the outdrive, not the engine itself. You should be propped to hit somewhere in the range of 4200-4400 rpm or so.