Whats the right rpm's

[controlled chaos]

Definately the props bro. It is gonna be like a new boat after you get those props dialed in. I don't know how the prop shops are in your area but the guy I use only charges me for one tune-up and then all the additional mods to get the props perfect (if any additional tuning is needed) are free. This is only during prop testing and when you are trying to find what prop is best for the boat. I would definately ask them if they do something like that.

Cheers,

Dave

[Deep C]

My buddy had a similar one he gets 4000+ on same wheels with 280 hp engines... It sounds that your gear ratio is different than his... Effectively "overwheeled". Our Viking is overwheeled... Now comes the trade out. If we ran with what we are supposed to we lose a knot and turn a lot of rpm on old engines.
I have just adjusted by reducing rpm and meeting "load" parameters of 80-85%...

My albemarle on the other end is under wheeled. I turn the hell out of rpm and have less speed than I should... Not so sure I like that either...

Dropping a couple inches out of your wheels would bring the rpm up where they should be...

[cdail28590]

I have 1.5-1 Borg warner trans. I am going to remove both motors and trans this winter to do some cleaning in the hull and when I put everything back in I am going to call a prop shop to see what they would recommend. I appreciate all the feedback as I wasn't sure what rpms I should be running and I definately thought my rpms were low. I hoping the prop shop can rework my wheels instead of having to buy new ones.

[Judith A]

Just a few ideas and not sure if you checked yet.Are they carbed motors and if so are the secondaries opening. also have you tried another rpm gauge my old boat had two on the tower that never went over 3800 even though it was running 4700.
My old boat was Albemarle 27 with Crusader vortec 350 port fuel engines with 1.5to 1 trans and 18x20 heavy pitch nibrals and I could get 4800 rpm loaded for a canyon run so something is oddly wrong with yours as I don't think it could be much heavier than mine
Mark

[Mackey]

I have a 27 Phoenix Express with a pair of Mercruise 5.7 carb'ed 260hp at 4500rpms. The trans are Borg 2.040:1 and swinging 17x21x3 with a #6 cup. With 300gals of gas and 2 persons and ice etc, I can run 30kts @ 4400rpms wot. With a light load, it will do 35kts @ 4500rpms. Hull design is very similar to the 28 Bertram and dry weight is 8,200lbs.

Those 5.7 engines @ 310hp with 1.5:1 trans should be able to swing a 17x17 props to 4200-4300 rpm wot. I do not see in the posts if you say they are 3 or 4 blade props. Also are the techs reading correctly? Have you actually had the boat weighted, 11,700lbs is the published dry weight of the boat? I am some what surprised that the trans are 1.5:1 and not 2:1 or better.

Base on BoatDiesel.com calcuator the 17x17x3 with a cup should be dead on for your boat base on the information in the thread. If they are 4 blade props and your weight is off, then you are about 2-3 degrees over pitched.

There is either some information missing or the engine are not right or the techs are not reading correctly.
But if your techs are correct and the engines tuned correctly, then those engine are way overloaded at 3700 wot.

[cdail28590]

The boat was weighed by the hauler when I bought it so the weight is correct. I haven't checked the tachs but it just would seem funny to have both tachs read the same. I would think it was a tach issue if one was different than the other. The only thing I haven't done is run the boat to full power and check to make sure the secondaries are opening. What are some suggestions on testing the tachs? The props are 3 blades.

[Mackey]

The boat was weighed by the hauler when I bought it so the weight is correct. I haven't checked the tachs but it just would seem funny to have both tachs read the same. I would think it was a tach issue if one was different than the other. The only thing I haven't done is run the boat to full power and check to make sure the secondaries are opening. What are some suggestions on testing the tachs? The props are 3 blades.

You need to borrow a phototach or get a mechanic with one and check the rpms of the engines while someone drives the boat. As you see, it a two man job. Which are most things when fine tuning engines on a boat. It would not be unusal for the techs to be off by these many turns on the upper end.
Since the boat was repowered with the 5.7 Vortec engines, they may have not bothered to check the techs. While you are phototeching the rpms, you can check that the secondaries are opening. Again those Vortec engines with the 1.5:1 tranny should have no problem swinging 17x17x3 props @ 4300 wot. Our boats are similar in hull design, you have more power, I have a better gear ratio and I turn 17x21x3 props with a heavy cup with no problem. 17x17x3 should not be a problem with 310hp and 1.5:1 gears. And remember you are basing that your RPMs are low on your techs, first thing to check are the tech reading correctly before you go changing stuff like the props' pitch. Actually you can check the techs at the dock, just need the boat running.

[cdail28590]

I'll check around and see if I can find someone local with the phototach.

[fishfighter]

With the info you posted,those engines with the trannie gear ratio and props,you should be hitting no less then 4300 rpms.I have a Wellcraft 2900 sportsbridge with twin 350's. The boat is a hair bigger then your Bert,but I have the same gears and wheels you have and I make 4450 rpms WOT with 200 gals fuel,50 gals of water,500lbs ice and 6-7 people on board with gear. Cruise rpms are 3100 with a 23 knot speed and a fuel burn of 1.1- 1.3 mpg.

Tachs must be way off. Who did the wiring? Did you change tachs when you replaced the prevortec engines? Also,are your engines FWC or Raw WC? 170F is the top end of the temp range if you are raw water cooled.Any higher,if you are running in saltwater,the salf will start plating out inside your engines. FWC,145F-155F is the norm,but hot summer water temps will raise that to as high as 170F.

[cdail28590]

To my knowledge no changes were made in the wiring or the tachs when the vortec motors were installed. The motors are FWC and run around 160 during the hot summer months a little cooler now. I plan on taking the manifolds and risers off and looking over them this winter when I take the motors out to redo the motor beds.