Tuning for ecconomy

**Mark** · 04-06-2004, 10:56 PM

I’ve just bought a 1994 150hp 2lt Mariner serial No. OG167001 on a fishing boat that has only done about 220 hours and appears in good condition.

I’m not really chasing more power as offshore you only tend to sit between 3800rpm and 4500rpm depending on the weather but would like to tune for best economy without any loss of power or torque.

What mods or tuning tips do you recommend?

Thanks in advance,
Mark

**baja200merk** · 04-06-2004, 10:59 PM

stainless prop

**Markus** · 04-07-2004, 02:17 AM

Stainless prop, raise the engine on the transom, cut the heads and run higher octane gas.

If you know how to jet an engine, make sure that it is not running rich at cruising speed.

**shadowman** · 04-07-2004, 05:35 AM

Maybe a Quicksilver High Five. The guys around here love them.

**Mark** · 04-07-2004, 07:26 AM

Hi Shadowman, a couple of people have recommended a 4 balde design over here from a company called Solas. They are similar to the merc props but apparently won't drop as many revs for the same pitch as a 3 blade. There about $350 Aust cheaper than the merc 4 blade props. Still expensive here though at $850 Australian (US$640). See solas.com.au and look at their torquemaster props under the stainles steel, merc section.

In saying that about 150~200 hours would make up the cost outlay based on fuel savings. They have a money back gurantee so it's probably worth a try.

I'm currently running a Stainless Steel 3 balde quicksilver 17" pitch. I'm not sure what model it is but it would be about a 1996 vintage talking to the original owner.

Current WOT lightly loaded gives about 5700rpm and 38knots.
Cruise at 4000rpm gives about 26knots.

Thanks Mark

**CDave** · 04-07-2004, 09:04 AM

I know this isn't the direction you are going with this thread but wouldn't a 3.0L or bigger engine get better mileage on that type of boat?

As far as maximizing what you have. Keeps fresh plugs in it. Try and trim for best speed without excessive RPM's and find a good prop, myabe a High 5 on that lil motor. Maybe a small setback jackplate so you can play with engine height?

This might help, http://www.mercurymarine.com/prop_selector

**baddjonny** · 04-07-2004, 09:48 AM

For a fishing style boat I would not turn that motor more than 5300 to 5500 that way you should be able to run motor down in the 3000 range also a ss prop for that type of boat is a waste of money and put's a bigger strain on the shift dog and causes more electroliss try a 4 blade merc alum. prop. Around $130.00here in the us. I know this statement is going to open a can of worms but on a boat like this it's common sense and economy.

my two
jon b

**Paul Vaillancourt** · 04-07-2004, 09:48 AM

Add a set of trim tabs they will get you on plan quicker and allow you to stay on plane at slower speeds as well as adjust the boat due to weight so it rides level from side to side. They worked great on my 24' Searay Sundancer. 28mph top speed, stays on plane at 3000 rpm @ 20 mph, before the trim tabs it took 3500 to keep on plane and the bow always rode up high.

**shadowman** · 04-07-2004, 11:16 AM

It will allow you to plane at a lower RPM. At least thats what Im hearing. Im sure going with the four blade will help also. I think alluminum props are too weak to rely on offshore

. Even then, with a single outboard I would keep my kicker engine tuned up!!

P.S. I think the trim tabs are a good idea.

**Paul Vaillancourt** · 04-07-2004, 05:36 PM

Mark,
I just noticed that you are posting from Down Under, I lived in Australia for 2 years. I lived in Melbourne. Goodday mate.
Seriously the trim tabs will also get you better gas milage. I tried a four blade prop also and it helped on the hole shot, but robbed top end, not that it was alot but you know.... I never put a stainless on it the props were always alum. the boat weighs over 5000lbs chevy 350, 260hp mercrusier I/O. Bone stock with 1600 hours.
Paul

**yamahadog** · 04-07-2004, 09:58 PM

4 blade props help a noticably on offshore boats as i run one to. try adding some setback maybe 4-6" solas props arent worth a sh*t in my opinion. and it sounds as if you are paying way to much for one i know over here they are about 300-350for a 4 blade cuz i used to have one. i like a trophy i think anyway 15p 4 blade on my cuz's grady white with a 225 yamaha but it will spin 6000 his boat is similar to yours i think yours being a little smaller boat and being a little smaller motor it would work out well you might try posting an add in the props section. but i know setback and 4 blades definitly helped on me and dads mako with twin 175 yamahas it is 22 ft they are 17p

**yamahadog** · 04-07-2004, 09:59 PM

also can you take a pic of you boat with the motor trimed level or all the way down i would like to get an idea of where it is mounted and i think we can help you determine the proper hight

**Terry Jackson** · 04-08-2004, 05:13 AM

The high 5 locks up hard with the water, with very little slippage, and gets better milage than 3 & 4 plades.
Leaning out your motor will help both fuel milage and power, but too lean and the motor WILL blow.
Aluminum props have a high coefficient of drag, and would get the worst milage of all, plus the fact they flex & have excessive slippage.

**Mark** · 04-10-2004, 04:49 AM

Hi Yamahadog & others.

Attachedd are a couple of pics showing the prop position compared to the boat. The boat is a (Cruisecraft outsider) they run a planning plank on the bottom of the fairly deep vee hull.
The hull has a 22 degree vee and the planning plank is about 5" wide at the rear and tappers away to nothing over about 10' of the boats length. The plank helps to plane slower and improves lift and fuel ecconomy.

The bottom cav plate on the outboard sits about 1" higher than the planing plank or bottom of the hull. This looks high to me and although the prop does tend to cavitate easily if put it into a hard turn with a bit of trim up I've been recommended to leave it where it is especially if fitting a 4 blade prop and then reveiw further from there.

I've only had the boat a couple of weeks and weather has only allowed 2 trips. I'll have a closer look when I go out tomorrow and see how far under the water the cav plate is when at a fast cruise of about 4200~4500rpm. I've been told to set up at about 1/8" under the surface at these revs.

Also the props look much cheaper in the USA so I may purchase one and bring it back in June as I'm planning to come over for a couple of weeks then.

Who is a reputable seller of props that I can have sent to my friends place ready for me to pic up. Obviously I need to be sure of what I'm ordering prior to purchase as it will be hard to make any changes once back in Australia. I'll get som more details from my prop and also list in another forum to make sure the selection is right prior to lightening of the wallet.

Cheers Mark.