38 Jarvis Newman

[John J]

Does anyone have experience with the 38 Jarvis Newman. I have one and it weighs 27,000 pds. loaded. 8V92 TI 550 HP, twin disk 2.04 to 1 gear, 29 X 28 Michigan dyna quad prop. The boat performs poorly and needs 400 to 500 RPM's to gain a knot in speed when accelerating . It tops out at 16.5 17 knots WOT at 2332 RPM. When underway it shoves a lot of water and leaves a huge wake. It handles all seas well , but lacks performance.
What is the best propeller for this boat and who is the best propeller and shop to adjust the prop for better performance ?
Any help or recommendations would be appreciated.

Thanks John J

 

[MDI45]

JohnJ,Have you tried a rope trim tab....a 1/4 or 3/8 '' rope tied tight around the transome.....it will push your bow way down

 

[John J]

Thanks for the reply, I will try the rope and do you think real tabs would work. I know Lee Wilbur and a few other Maine builders told me trim tabs don't work on these hulls.

 

[cb34]

tabs

If the boat is not balanced correctly, or just too dam heavy tabs will help

 

[traditions]

That boat needs a 2 1/2 t0 1 gear with a bigger wheel.Not really a speed boat to begin with.

 

[Powderpro]

Considering the weight of your boat, I think 16.5 - 17 knots is probably as good a number as you can expect from 550hp and a 29" diameter prop. When you say "When underway it shoves a lot of water and leaves a huge wake", that's telling me that the boat weighs too much to get real good speeds, even if you had 700hp and the best prop in the world. The huge wake means the hull is sitting too low in the water (it's heavy) and I don't think a prop magician is going to get you any noticeable improvement in speed. A lower reduction and bigger diameter prop (if you have room for a bigger prop) like Traditions suggested would be more efficient, but unless you shave some weight off the boat, I think you may be stuck at your current speed.

 

[MASTERENEGADE]

I have a similar problem with my 35ft jc. She is very proud in the bow. The rope does bring my bow way down. I also just recently been doing prop adjustments and experimenting. I took all the cup out of my prop and has helped drastically. And i am maintaining good speed with the newer prop(still 200rpm off top rpm).

But i am next lean towards mounting wedges on the bottom of the hull next spring to help bring the nose down a lil bit. My next test is gonna be which size rope brings the bow down and gives me the best performance to determine what size wedges i will install.

I do not want to mount tabs for numerous reasons. More hardware, cored transom, more things to go wrong and break. I fish with the boat and cant stand leadering fish away from trim tabs. If the hull was from the factory with tabs built into the transom i would feel a lil differantly.

Try the rope first and see how the boat behaves

 

[John J]

Thanks for the information I will try it.

 

[tunaorlater]

I tried he rope trick on my nb a few months ago. I don't need to lower the bow but was curious what it would do. I used a 3/8 rope and the bow probably came down 2 feet. I never thought it would make that big of a change, the water damn near came over the bow.

 

[MASTERENEGADE]

It makes a huge difference, when i have a full crew 6 passengers, a deckhand, myself and fully loaded with bait ice and fuel, i use a 1/2" or 3/8" to help level her out and it picks up my cruise speed top end it can hurt a lil due to the drag.