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Year

89 Evinrude 88 SPL rpms?

slapshotjh I have a 1989 Evinrude 88 spl with a 13x19 prop pushing an 18 foot sea pro center console.

With just me in it and not much gear, the boat turns a maximum of 4800 rpms and 31 mph. Should I be using a different prop? Should the motor be turning in a higher rpm range.

I have fresh plugs in it and 87 octane. Any help would be appreciated. The motor is mounted in the lowest slot on the transom if that helps, and it has power t/t.

Thanks,

Jon

2001-07-09
Dhadley You're 1000 rpm too low. Raise the motor to get more WOT rpm's. Change the prop as required. What brand/style prop are you using now?

Good luck!

2001-07-09
slapshotjh I got it cheap $130 at West Marine.

It is a Michigan Wheel, I believe. The blades appear to be cupped.

How high should I raise the motor?

I am new to all of this. You suggested changing the prop as required. Which way should I go?

I tried a 13.75x15 for a little whie. The boat revved to 5800, but I lost top speed considerably. I feel that the boat should be travelling at 35 mph or better. Am I expecting too much?

Any more help you can give will be greatly appreciated!

Jon

2001-07-09
Big Rod slapshotjh, My 2 cents worth, I think, from past experience, a 17" pitch would put you in the 55-5600 RPM range (good place to be) and if you don't mind a little sweat, the trial & error method for optimum height adjustment is worth the trouble. The highest adjustment on transom possible without cavitating in turns. Keep tring til you get that 35 mph, it's possible... 2001-07-10
slapshotjh I had some time to work on it this evening, I raised the motor one notch up from where it was at the bottom.

I was fooling around looking at the throttle positions in relationship to the linkages on the carbs to open the butterfly valves. I can push the butterfly valves open further with my thumb after the throttle has reached WOT on the console. Do I need to adjust this so that the butterfly valves are fully open (I am assuming they open 90 degrees?)

Will test the revised motor height tomorrow. Will get another prop this weekend.

Jon

2001-07-10
Big Rod You are very close to insuring W.O.T. Remote fully open and butterflies fully open. At this point the throttle stop screw must be set to prevent the butterflies from opening further than perfect horizonal. Operate the remote a few times and reset as needed. Now would be a good time to check advanced timing (ball park). 2001-07-11
slapshotjh I will adjust the throttle stop as needed. How do I check advanced timing? I do have a timing light that I have used for automotive purposes. 2001-07-11
slapshotjh Well, raising the motor one notch gained 2-3 mph. However, top rpm still seems to be 4600 rpm. Will jumping down from 13x19 to 13x17 prop raise my rpms and give me more speed? How about that timing? 2001-07-11
Big Rod You must first find top dead center (TDC) for #1 cyl. Notice the timing pointer above top carb. pointing at flywheel teeth. It is adjustable and should point to TDC when you have confirmed the #1 piston is at TDC. With timing light to #1 cyl. you are read 2001-07-11
Big Rod About the prop, I don't know if the 17" would be worth spending the money, but if you had access to a loaner I would certainly give it a try. 35 MPH or bust! Good night #2 2001-07-11
J.B. Cornwell What you've done so far is good. I think you really need to try that 17" prop. It should bring you to optimum rpm (about 5000-5500rpm)and top speed at WOT of around 35mph.

Red sky at night. . . .
JB

2001-07-11
evin300 Slap, this would be a good time to consider a OMC SST stainless propeller. The SST is a cheaper alternative to a polished prop. (they are generally painted black) The older ones were telflon coated and I think the newer ones are powder coated. There are m 2001-07-12
evin300 In Ebay search type: OMC prop* 2001-07-12

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