91 celebrity first splash, issues??

[MikDee]

IMO, Your doing more the 41mph!, it looks more like 45 at least.

 

[MikDee]

IMO, Your doing more the 41mph!, it looks more like 45 at least.

Oops! missed that last post you made, was that trimmed out, or not? If not you'll pick up a bit more speed. By the way, that looks like a generic not very streamlined "all around" prop on there, it might be made more for power, then speed?. I don't think it's Merc prop. The key is to have the right prop, I think a cheap Merc Black Max 21P Alum. prop would do even better then that? There are also better props out there then these, but you need to get some input from the Prop Guru's on here, for the best choice.

 

[voodoochikin]

the prop is a Michigan wheel 14x19P stainless. and yes trimmed to the sweet spot. one click higher and it was ventilating (proper term?) and one click lower and id lose speed. Im worried that a 21P prop will drop me below 4,000rpms.... ill be checking the timing soon, before going in the water again. 8* btdc initial.. and total advance of 32*.

 

[MikDee]

I was right, it figures. IMO, a Michigan wheel from what I found is an okay reasonably priced generic all around prop. I'm looking around to see what might be a more streamlined reasonable prop. I know the Merc Black Max alum props are a step up, and better then that. I've been reading good things about the "Turning Point Hustler". Either way, I don't think you should go less then a 21pitch prop. I think a 19pitch would cause you to overrev.

 

[voodoochikin]

Maybe Im confused.... but I have a 19p now.... how would switching to another 19P prop cause me to over rev, considering Im at 4,100rpms WOT now? and 19p was what came factory on the boat I believe. Also I thought sticking with stainless steel props was the way to go?

 

[bruceb58]

Verify your RPM with a shop tach. I wouldn't go to a 21" prop. The prop you have sounds like the correct prop. Is your prop in perfect condition? No dings in the blades or tips?

You don't have one of those aftermarket fins on here do you? If so, take it off and leave it off.

 

[voodoochikin]

Nope no fins... Lol. The prop is clean as far as dings and kicks BUT...it looks like someone took a sanding disc to it to attempt to clean it or something. I thought it was scale... Buy closer examination shows swirls and its very rough to the touch...could this really be eating rpm's and 10mph? Lol. Idk what my deal is but part of my search was for a 55mph boat. And dangit..I wanna get there haha. No access to shop tach but do have access to another standalone tach. Its pole adjustable.. What would this charging system be called? As far as poles go.

 

[MikDee]

There is a lot of difference in prop design, the basic Michigan wheel is an all around design. The Black Max is basic Merc Alum prop, but a better design. The Solas Amita props right here are rated pretty good, and are on sale, & reasonable. Here's a link from MercuryMarine that might help, Get whatever pitch your happy with, but if the prop is more efficient you'll probably get more rpm's out of it, and even more when It's fully trimmed out. It sounds like you've done a pretty thorough job of going over the engine, maybe the stock prop is holding you back?

http://www.mercurymarine.com/propellers/advantage/overview/

 

[thumpar]

What drive do you have? My 5.7l with Bravo will go full up on trim with no ventilation or porpoising on a nice day. Even on a rough day it will not ventilate just porpoise with the trim full up. Some days I wish I could go a little higher.

 

[voodoochikin]

Alpha one.

 

[bruceb58]

BUT...it looks like someone took a sanding disc to it to attempt to clean it or something. I thought it was scale... Buy closer examination shows swirls and its very rough to the touch

It's possible that the prop was repaired at a prop shop who didn't know what they were doing and you have a blade or two that weren't repaired properly and don't have identical pitch.

 

[Maclin]

Voodoo, that rough spot with no paint could be from cavitation. Cavitation will burn the edges of a prop, and take paint off in odd patterns. The cavitation could be from those brief periods of trimmed too high before dropping it back down.

 

[Maclin]

BTW, I like to start off with a prop refurb (or new known prop) with any new boat so I know where I am at before getting any performance numbers.

 

[voodoochikin]

maclin--- the entire prop is like that.. it wasn't painted as most stainless props are not painted. Its obvious that a sand disc was used on it.. if you ever used a grinding disc on steel, you know the marks it makes. there are some spots where it wasn't sanded and those shine like polished stainless lol.. I plan on checking timing tonite or tomorrow. My friend is dropping off his adjustable timing light. IS IT SAFE to rev the motor to 4400rpms+ with just running on the muffs?? Im real nervous about chewing up the impeller in the lower unit water pump.

 

[MikDee]

No! It's best to just run at idle, and do not run the motor past 1500rpm on the muffs, in fact that rpm should not even be held for long, or you'll cook the impeller. Also please avoid over revving a free running motor, it's made to run under a load, or you can cook the rings, and glaze the cylinder bores from overspeed of the pistons.

 

[voodoochikin]

Then how do you check your total advance if not being able to run the engine up to the rpms when all your timing advance is in?

 

[NHGuy]

You can briefly burst it to around 3000 which will show you your all in timing. Don't go past 32 with Thunderbolt 4, they have no knock sensor. If it turns out to be TB 5 and has the sensor just set the base timing and let the controller manage your advance. Reason I said to verify presence of the sensor is that some say there are TB 5's without them. Maybe there's confusion. My boat and steel single axle trailer weighed 3250 last check. So I think the boat is 2400, no proof though. It did 59 mph on gps at 4650 rpm with a 23 pitch Michigan wheel aluminum last year.

 

[bruceb58]

You can run it up temporarily to see the advance if you have a good water flow at the muffs.

 

[voodoochikin]

Iboats specs show my boat to weigh aprox. 3050lbs dry. With 3/4 full fuel tank (40gallon tank).. engine fluids. some gear. and a heavy tandem axle trailer. It all weighed 4060lbs on the scale. sooo.. 4060 - 3050= 1010lbs... subtract 190lbs for 30gallons of fuel.. 820lbs... im gonna go ahead and say that 820lbs sounds about right for this beefcake trailer, and some gear. Which leaves me feeling somewhat good that most likely the boat is not a watter logged pig.. haha. BUT I did find out the carb (q-jet) was recently serviced/rebuilt.. and I have a feeling it wasn't done properly. Is a quadrajet for marine use different than one for automobiles? if not.. I can service it correctly myself.

NHguy... Im jealous of your speed. Id love to top out about 60mph.. most evenings the lake where I go is glass... so its fun to toil around out there on smooth water. feels like endless freedom.

 

[500dollar744ti]

You can get a rebuilt carb for less than $400 on ebay. I ended up doing that in lieu of rebuilding my carb and have no complaints after 3 seasons. I was in a position where I needed the boat back on the water quick and didn't have time for a screw up on my part.

I also suggest looking at Solas HR-Titan 3-blade stainless props once you get you engine delivering full power. My 23' Cobia weighs in at about 4500lbs loaded and I got 6mph top end out of the 19p HR-titan 3 prop vs the 19p turbo stainless prop that was on there. I'm now at 51mph @ 4400 trimmed out with just me and I can get 47mph with 8 people. The old 19p turbo prop would do almost 46mph with just me.