increase horsepower and speed

[desperado8156]

have a 25' sea ray with a 225 in it. Is there anything I can do to increase my horsepower and speed in this craft. I read about having a clean hull etc, but is there any modifications I can do to goose up the engine output, like having the head ground, piston change, prop change ( to what pitch )I'm not looking to challenge any hydroplanes, just get it up to about 45. Now I only get about 30. Its a 1973 W/E and so clean it's worth the trouble. Thanks

 

[Franki]

Re: increase horsepower and speed

Normally I'd say save yourself the trouble.. outboards are not as easy to "hot up" as other motors..<br /><br />Things you could do that might help.<br /><br />1. Is it proped correctly??? what rpm is it doing at 30mph???<br />2. Maybe boyesen reeds might give you a bit more punch..<br />3. If you are really keen, take your block and heads to a machine shop experianced in porting 2 strokes.. if they are good at what they do, you can get a boost..<br />They could also shave alittle off the heads for more compression, and mess with the jets to utilize it...<br /><br />All of that is gonna be pretty expensive though..<br /><br />number one thing you can do is make sure its propped correctly..<br /><br />If it is propped correctly, then I can't see even all that work getting you the extra 15 mph.<br /><br />Just make sure, that when you are at WOT, that the engine is doing its max rpm's, if it isn't, you are not propped correctly.. <br /><br />Go see a friendly dealer and try some different props with his advice, you might be surprised at the result....<br /><br />rgds<br /><br />Frank

 

[steelespike]

Re: increase horsepower and speed

D, a 15 mph increase on your boat would take <br />some serious horsepower unless you are getting subpar performance to start off with.<br /> Im assuming its an IO. but we need to know<br />exactly what style boat.Full cruiser, true deep v<br /> hull weight.How much payload etc.<br /> What size prop what rpm at wot.<br />You should check out the motor especially the compression.Would be good to check for wide open throttle and check the timing.

 

[wilkin250r]

Re: increase horsepower and speed

I've put nitrous oxide kits on small motorcycle engines, I don't see why you can't put one on a boat motor!

 

[moderator1]

Re: increase horsepower and speed

Moving to I/O's.

 

[Bondo]

Re: increase horsepower and speed

Just WHAT IS This 225 engine ????? Ford, Or Chevy ??? my book shows Both...... Either are Capable of over 300hp... Comes down to $$$$$....<br />As Spike States... It'll take A Bunch of Horsepower$ to Gain 15mph..!!! Then the Question comes up,?? Will the Outdrive Take It ????

 

[boatingfool]

Re: increase horsepower and speed

Your not going to get a 15mph increase with your boat usuing the same motor.<br />If you are looking for that drastic of an increase in speed you will need a bigger motor.<br /><br />Some may say you can get there with the motor you have with enough mods but even if you could it would be cheaper and quicker to go bigger.

 

[ob1jeeper]

Re: increase horsepower and speed

desperado,<br />I'm with boatingfool on this one. a 50% increase in speed is going to require a BUNCH more HP (likely in the neighborhood of 375 or more) to get the power to turn the prop you iwll need to obtain 45... AND like was pointed out earlier, the outdrive will be taxed pretty heavily too...<br /><br />Better durability, better performance, and WAY cheaper in the long run, to go to a matched motor & outdrive pkg. properly sized for your SeaRay, than to try to increase HP enough to get that level of performance out of these parts...<br /><br />While once modified, they may hold up for a couple of weekends, within a year or so, you'll likely be on the end of a tow rope home (provided the rods don't go out the side of the block, and through the hull, or start an oil fire), and then you'll be replacing $$ parts...<br /><br />At least if you size up now, you'll be able to recoup some $$ selling these parts as used, or trading them in on the bigger stuff...<br /><br />Good Luck, Obiwan Jeeper

 

[Seaboo2]

Re: increase horsepower and speed

My thoughts exacatly ob1. He can get the umph he wants from mods., but the cash outlay is hardly gonna be worth it. If he does do mods. it wont hold together too long. (I've had SEVERAL of my hot rods (he11 raising days) come home behind a wrecker to be built again.). I/O's are alot like a car they can be made to run but with any hop up, reliability (an inportant thing in a boat) goes down.

 

[hydrabass]

Re: increase horsepower and speed

i worked for them for years and done several different engine set up on alot of different models and i'm not sure a 5.7 would get 45 mhp on a 25' boat but changing to a v8 you have to consider your x dimension [the location of your outdrive on the transom ]would be different, your stringers would have to be changed and your risers have to be a certain height above the water line to keep from ingesting water into the engine .

 

[Rob Lung]

Re: increase horsepower and speed

I just put a new rebuilt 7.4L in a 268. TRW pistons and a comp cam = 375 hp vs the original 330hp. Net gain 7mph, she used to do right at 35 now a little better than 40. The big differnce is out of the hole i.e. push throttle down boat planes out, ahhh <br />I know it gets old but there is no replacment for displacment!

 

[John Carpenter]

Re: increase horsepower and speed

Well boys & girls...what we still don't know is...what engine is in the boat, what prop is on it and what the rpm's @ WOT are. Without that info it is not possible to make suggestions. With that year and hp. rating, it could be either a 305 or 350...if it's a Chevy. Neither engine is going to push the boat to 45 mph. but should do better than 30. Bottom line is we need more info.

 

[magster65]

Re: increase horsepower and speed

A 225 that year I think is a merc. 305 w/4 bl. carb. I had an '83 22.5' SeaRay with the 305 w/2 bl. carb. in perfect tune and I got 35 mph (power tuned, waxed hull and optimized prop). Those older SeaRays are very sturdy (excellent boats) and therefor heavy so to get 45 mph+ in that vintage I think it'll take a big block. You might get upwards of 40 with a 350 but a 305 won't do it. There's no replacement for displacement (generally speaking). If it were mine and I had to have better performance I'd just do a few little things and be happy with what it got for speed because it's not a 'speed boat'. Put a nice aluminum manifold and (approved) carb. on it, make sure the ignition is working properly, get a free flow exhaust system and wax the back half of the hull. Fine tune your jetting and timing, then play with your prop until it's 4200 +/- a little at WOT with your drive trimmed where it's happy. Make sure there's not a lot of extra 'stuff' in the boat too. Every little thing makes a difference. A lot of little things make a big difference.

 

[charleswmoore]

Re: increase horsepower and speed

Since we are only speculating I would assume this is an I/O on a 25' boat how about adding DUO-Prop?<br />Without a lot of internal boat mods this would be easiest and most productive because I'm sure that a 20 year old stern drive is ready to detonate at any time anyway. The whole package will run in the neighborhood of 12.5k. But we just won't know because desperato has left the room

 

[mkast]

Re: increase horsepower and speed

You can either spend your money on another boat, or wish you spent your money on another boat. Too big, too heavy. By the time you convert to a big block you'll find out it's time for a boat that was designed more for your purposes.

 

[sundancer270]

Re: increase horsepower and speed

It's a Cruiser So Cruise. If you want faster.Buy another Boat. It would cost to much to add everything for a mere 6 or 7 miles an hour.