Need Help with setup!

[Boilermaker]

I have a 1978 Johnson 115Hp on a 1971 Westwind 180>>>Modified Vee runabout. Engine has low hours>>>boat was in storage for over 20 years.<br />I was running a Johnson 14x17 aluminum prop with wot at about 5300RPM. <br />Put a Stiletto 17"pitch prop on and killed the holeshot, and dropped WOT to about 5000RPM.<br />The engine was on its lowest setting, so we raised the engine up 2 holes>>>A.V. plate is now about an inch above the keel. <br />Since changing the X-dimention, the rpm only raised to 5100/5200 rpm with the engine trimmed up to just before venting. <br />I MAYBE gained 100RPM & 1 or 2 MPH top speed????<br />Top speed is 36 MPH on GPS.<br /> This boat/engine combo would pull me up on one ski when I was in my 20's and over 200lbs with the OLD OMC 13x19" Alum. prop, that prop spun the hub. Now It has a SLOWWW time to plane with no skier. <br />There is no floatation foam to be waterlogged.<br />The tach was new 2 summers ago, its a Teleflex.<br /> It is a heavy boat, but I think it can do better & was surprised by such small if any improvement after changing engine hight. WHAT SHOULD MY NEXT STEP BE??? Please help!<br />Thanks <br />Jim <br />

 

[Dhadley]

Re: Need Help with setup!

Its no surprise that the Stiletto has more bite than the 17" aluminum (hence the less top rpm) but I would have thought youd gain more speed. The Stiletto definately has more lift so it may show less rpm but the speed should increase.<br /><br />When, in the trim range, does it vent? 1/2 way, 3/4 or almost to the end of the travel?

 

[Boilermaker]

Re: Need Help with setup!

Aprox.. 3/4 if going straight.<br /><br />I am not sure of the speed with the Alum. props>>>I didn't have a GPS until recently, but the rpm report is accurtate. Should I switch back to the alumn. prop to see what it does??<br /><br />I just did the engine hight last week. I would have thought more RPM's AND speed from the x-dimention change of 2 holes though??? <br /> THANKS DHADLEY!!!!

 

[Dhadley]

Re: Need Help with setup!

Yes, try the old prop again but remember -- we're 2 holes up from when you ran it last. That may be OK. Just see what you get in a straight line, dont worry if it vents in the corners. <br /><br />Venting at about 3/4 trim indicates we're about as high as the hull/prop combo likes for now.<br /><br />I'm real curious about the lack of increase in speed. Lets try something -- next time out, and with either / both props, with the boat just barely on plane take notice where the water "breaks" from the hull. It doesnt have to be exact, just a general idea. Then slowly increase the r's. Lets say 300-500 at a time. Then notice where the water breaks. Do that all the way to wide open.<br /><br />What we're looking for is how the hull reacts to increased rpm. When the boat is just on plane the water should break from lets say, 1/2 way forward of the transom. It doesnt matter where right now. As you increase the rpm / speed the "break" should move further back. How much doesnt really concern us to start with. We just want to know if the "break" -- at any rpm -- actually moves forward rather than back.

 

[Boilermaker]

Re: Need Help with setup!

Thanks Dhadley!<br /> When I'm checking where the water breaks from the hull, should I just set the trim for the best RPM at planeing speed & then leave it alone???

 

[Boilermaker]

Re: Need Help with setup!

Dhadley, do you think I may have some other engine issue that is limiting power??? The engine probably has about 300 hours (if that) on her. Do you think my boat's performance is normal for a 115hp engine??? I don't know the weight of the boat, but it doesn't carry a lot of fuel (24 gals) & is 17.5 ft from bow to stern. And it doesn't have much deadrise.

 

[Dhadley]

Re: Need Help with setup!

Ah, the trim -- good point. I started to talk about that and the office phone rang -- work got in the way again!<br /><br />Yes, at each setting play with the trim to see if we can change the break point (get more of the bow up and out of the water) or if the trim has virtually no effect. <br /><br />Actually a 17 1/5 boat should be swinging a 19, I would think. The 17 should be good for skiing. I assumed the motor was in good shape and running right. From your other posts you seem to have a good grasp on checking out the basics.

 

[Boilermaker]

Re: Need Help with setup!

I thought a 17" pitch would be a good all around prop. The boat is heavy for its length>>>a lot of freeboard as you can see & it is a 1971, so its probably way overbuilt.<br />The engine sounds strong, but I think I will do a de-carb again,and check compression>>can't hurt and its been a while. The carbs are clean & the plugs look good. The only thing I haven't checked is the spark strength>>>I don't have a tester to check spark at 1/2" gap. I will have to come up with something.<br />The ignition coils & wires are originals. The wires look amazingly good, but the iron cores on the coils are pretty rusted, and I was worried that the ignition might have been weak and cutting my top rpms. Also am seeing unburnt fuel in the lower engine pan and on the "mid-leg" after running??? I don't remember seeing this years ago.<br /> I just don't understand why the revs didn't increase after the x-dimention change??? Seems to me that it should have increased a few hundred rpm's more then it did from less drag.<br />I will get back to you on where the water breaks when I get back on the water.<br /> Sorry my posts are so long>>>I'm trying to be accurate.<br /> THANKS AGAIN!

 

[Dhadley]

Re: Need Help with setup!

Accurate posts are always good. No matter how long. <br /><br />Keep us posted!