kevellis32

I have a boat with a 1986 3ltr 4cyl mercruiser motor in it and I am just wonderin if there is much that I can do to get more power out that motor safely. The motor runs great, just needs alil more push if I have the boat filled to capacity and I want to pull a wake boarder. I have tried different props, they make a little difference, just not exactly the difference that I want. Any suggestions?

P.J

Swap it out for a 305.

I think to get a skier up you are going to need more HP than you can squeeze out of a 4 cyl.

Pop-Pop

Big trim tabs will help to keep the stern from digging a hole. Otherwise, get rid of as much weight as you can from the boat, including more fuel than you need. Any people on board should get near the front to reduce stern squat. Of course one of the biggest things is to make sure anyone trying to get up uses a technique that does not put a lot of unneeded drag on the boat.

greasemonki

there isn't really a whole lot to be done to a marine engine to boost performance and still retain reliability. They run high rpms for extended periods, so everything needs to be in a "comfort" zone at higher revs. The little 4 banger mercs really don't put out much power, a smaller prop (either less pitch, or smaller diameter) will get it out of the hole faster, but you will lose top end, and you'll have to watch for overrevving. Those hydrofoils (doel-fin, etc.) that attach to the cavitation plate (technically the anti-cavitation plate) work pretty well, they help the boat plane quicker, and stay on plane at lower speeds, they are only about 50 bucks, and simple drill and bolt on install, they also give skiers and swimmers a nice step to climb back on the boat with (just be sure they step close to the outdrive so there isn't too much tweaking going on on that plate).

ftltmp

I agree with greasemonki, your best performance is going to be in the prop, you might experiment with different pitches or 3-4 blade props but you are talking money.... B_O_A_T.. Break Out Another Thousand

ratat98

Hmm There's a mercruiser factory just down the street from me..Want me to go see if I can "borrow" anything from them?

gerry

If it is an open Bow and even worse if it is a tri hull they are very light in the front.. A lot of your power is going to raising the bow of the boat instead of going forward.. move as many people to the front of the boat as you can safely do and it will help it move forward rather than up.. Once it has planed out you should have plenty to keep the skier up..

Also if pulling up a skier have them start on 2 skis and then Kick one in a safe spot once the boat comes up on plane.. If they are not experienced skiers then an under powered boat will be very difficult for them to get out of the water with one ski..

Gerry

kevellis32

The boat can already pull up a skier no problem, I just want more power. But thats what i figured

TonyB

Some good resources...

http://correctcraftfan.com/ They are more specific to Ski Nautique, but they do have good info, particularly for the engines.
http://ebasicpower.com/ Good engine resource, if you want to repower the boat

HTH

Tony

89dieselkong

Remember, too much more power and you will be past the capabilities of the lower unit. I think it is the Alpha 1 drive that comes with the 4cyl.?

kevellis32

Yea its an alpha 1, they can easily handle around 225hp that comes out of their small block V8 from the earlier years. I'm just trying to find something that may give me 10-15hp. I was wondering if a MSD marine ignition or something of that sort, better spark plugs, throttle body spacer(if made for the engine), or a better carburetor would do much.

I got the boat last year when the boat shop that I bought it from thought it had a blown head gasket and I knew that wasn't even close to the case. I pulled the motor and outdrive and completely rebuilt both. It turned out that all that had happened was the drain plug was left in, the boat sat uncovered for a year or so and water was able to work its way through the oil pan gasket and filled the motor with oil so i fixed that and the second I had everything back together the motor fired up on the first shot.

bnold

Prop size is key... I have a mastercraft X-30, but I also have a 70 Bonanza heavy fiberglass boat with a 65horse 3cyl merc on it... I can ski behind it with 3 people in the boat no problem...