Extra HP on a 1974 Silver starfilte 135

[myabuttz]

Ok a new topic: Its time to get the boat out and run around the lake. So I was wondering if there is any way to make my boat go faster. Its a 1974 Evinrude Silver starflite 135 HP. I had the motor rebuilt because of a broken ring 2 yrs ago and just had a new shortblock and pistions but on so now its a 140 HP. Is there any other way to get more power other than bigger carbs.? I thought about NOS but do you think it might blow the motor?

 

[Chinewalker]

Re: Extra HP on a 1974 Silver starfilte 135

Hi Corey,<br /> The 140 was about the upper limit for the 99-cubic inch powerhead. There's ways to get more out, but not as a simple bolt-on and go. Easiest way to go faster is to get a bigger motor. <br /> Of course, there's also plenty of ways to maximize what you've got. Are you propped to the upper 5000s RPM range? Is the motor as high on the transom as it will go and still maintain a solid bite to the water and still pumping water? Is the boat's bottom clean, crisp and straight? Is the boat as light as possible - not carrying any water-logged flotation foam, spongy stringers or excess baggage/cargo?<br />- Scott

 

[DJ]

Re: Extra HP on a 1974 Silver starfilte 135

Good advice from Chinewalker.<br /><br />Forget the NOS. If you do it wear a kevlar vest and helmet because you will have a grenade behind you.

 

[myabuttz]

Re: Extra HP on a 1974 Silver starfilte 135

well the motor runs 5400 RPM now. Boat's clean and good bottom. but its a heavy boat with an average weight of about a ton. 18' fiberglass Crestliner.<br />about the NOS I was thinking a smaller booster nozzle like 20 HP maybe. Still might be too much though.

 

[Chinewalker]

Re: Extra HP on a 1974 Silver starfilte 135

You've just spent a fair amount of money and time getting the motor going. Any mods you make will severely cut back on the amount of life left in the motor, to be measured in minutes, not hours. There's a reason OMC never offered the 99-cubic inch V4 as a 160hp, or even a 150hp - , it was simply tapped out at 140. Of all the OMC V4s, the 140s typically have the shortest lifespan because they have the smallest margin of power vs. reliability./longevity.<br /><br />Can you get more power out of it? Yes, but it would involve a lot more than simply bolting on a go-fast part. If you spoke to someone who really builds the OMC V4s, (DHadley, for instance) he'd probably tell you to start with the crankshaft and build out from there, particularly if you want something that'll last for more than a few passes by the pier...<br /><br />- Scott

 

[R.Johnson]

Re: Extra HP on a 1974 Silver starfilte 135

An 18 Ft. Crestliner is not a performance boat. The rule for going fast on water, " lot's of motor, very little boat" You could throw a lot of money at a boat like that, and gain very little.

 

[myabuttz]

Re: Extra HP on a 1974 Silver starfilte 135

alright thanks guys

 

[myabuttz]

Re: Extra HP on a 1974 Silver starfilte 135

is it possible to re-gel coat the bottom of a fiberglass boat?

 

[myabuttz]

Re: Extra HP on a 1974 Silver starfilte 135

and, I have a 13x19 prop now. which one would make it go faster?

 

[DJ]

Re: Extra HP on a 1974 Silver starfilte 135

If you are turning 5400 rpm now, leave the prop alone. Even at 5400, you could use a few more RPM's. Propping up is not the answer, you will lug the engine.<br /><br />One other thing to remember. Your engine is really not 140 hp. It was not until 1983 that hp was measured at the prop. The 99.6 cid engine was never rated at more than 115 after 1983.<br /><br />About the only thing you can do is make sure you are optimizing your set up. You can set the engine up one mounting hole and see if you gain any speed. You can keep going up until you start to experience prop ventilation and/or cooling problems.<br /><br />Yes, you can re-gelcoat a glass boat. It's not easy or fun. If your hull bottom is bad, painting is much easier.

 

[ledgefinder]

Re: Extra HP on a 1974 Silver starfilte 135

Ditto what these guys are saying on pushing a 135/140 more. They run pretty close to the margin stock. I see lots of 85s & 90s that still have healthy powerheads, but every 135 I see is burned out. They'll run WOT 24x7 if they're mechanically in good shape (clean carbs and gas, timing right, good cooling) but the margin for error is slimmer than the 115s/85s etc..<br /><br />As Chine said, get the motor up as high on the transom as it'll run. Then see what you have for rpms.<br /><br />OK, that said, if you REALLY have to take chances, take a look at the recent post on hopping up 135s here, with DHadley and others. Also, www.screamandfly.com is a high-performance outboard site that occasionally deals with the old crossflow V4s. You can square off the ports (requires teardown), mill the heads, mill the divider wall down in the intake plenum, open up the exhaust (your neighbors will love it...), lots of stuff. Except for squaring the ports and doing the plenum, you're pushing the engine with all these things. <br /><br />Or, just put the motor on a 12' jon boat...

 

[myabuttz]

Re: Extra HP on a 1974 Silver starfilte 135

yeah on a 12 footer it should really fly. I have original Brochures on it saying it can go up to 70 MPH (i'd like to see that)

 

[Mercathode]

Re: Extra HP on a 1974 Silver starfilte 135

Corey what did they do to this "rude" to make it a 140 from 135. In 77 OMC double drill the exhaust and gain an extra 5hp. I was wonder what your guys did?<br />LW

 

[myabuttz]

Re: Extra HP on a 1974 Silver starfilte 135

we had a new power head put on when a piston ring broke and tore up our old one