1996 88hp Johnson, 1987 McKee 17 ' offshore

[surrender]

Ok, older boat/motor combo. Cant find on prop what size it is. What size would anyone recommend? Not looking for miracles, just decent performance. Present prop is a three bladed aluminum one. Again, cant find on prop what size it is. Prop has some rust like material on it and what looks like thick paint on inner hub so if it is marked there I wont see it.

 

[Dhadley]

Re: 1996 88hp Johnson, 1987 McKee 17 ' offshore

Just a guess based on what we used to run on them and with the limited info provided - probably a 13 1/4 x 17 if the motor is mounted all the way down with a 2-3 person average load. If the motor is mounted up a bit maybe a 13 1/4 x 19. How worn is the prop?

Send / take the prop to a prop shop and they can measure the diameter & pitch for you.

 

[surrender]

Re: 1996 88hp Johnson, 1987 McKee 17 ' offshore

Thanks you sir... Have a great prop guy here in Wilmington,NC. Used to take all my inboard props to him when I was working sportfishing boats. Gonna do some running with what I have and check speeds at different rpms paying attention to people on board, fuel, ect. I think I can borrow from a vendor here to test out what will be best. He has tons of used stuff. Could end up I already have what I need. Oh yeah, prop has some minor dings but not really worn. Dont think the boat got used much by previous owner, kinda neglected.

 

[surrender]

Re: 1996 88hp Johnson, 1987 McKee 17 ' offshore

Just a guess based on what we used to run on them and with the limited info provided - probably a 13 1/4 x 17 if the motor is mounted all the way down with a 2-3 person average load. If the motor is mounted up a bit maybe a 13 1/4 x 19. How worn is the prop?

Send / take the prop to a prop shop and they can measure the diameter & pitch for you.

Prop is a 13 3/8 X 17. Boat ran 32.9 mph at max 5300 rpm. Any thoughts?

 

[Dhadley]

Re: 1996 88hp Johnson, 1987 McKee 17 ' offshore

Not bad but the rpm could come up a little. Check the motor height. With the AV plate (plate above the prop) parallel to the keel see where that plate is in relation to the keel. If it's below the keel the motor can probably come up some. That will pick up the r's some. With an aluminum prop you may not be able to come up more than about an inch above. At any rate the AV plate should not be below the keel.

 

[surrender]

Re: 1996 88hp Johnson, 1987 McKee 17 ' offshore

Thanks D, I think the rpm issue was a carb deal. I was checking where all the fuel was coming from and took the cover off the carbs and pumped the primer, tons of fuel would pour out the carb. I think that meant my float and needle was not seating right. Took carbs back apart and cleaned and re set needle. Did blow test and it sealed. Reassembled and it worked. Bulb stays hard. Will test this week. I still changed the coils because boat ran great until it warmed up then would only get to 5000 and stumpled out of the gate. old coils did not produce a great spark on a tester.. Hope to find out soon.

 

[surrender]

Re: 1996 88hp Johnson, 1987 McKee 17 ' offshore

Ok fixed bottom carb and changed coils. Boat runs strong. comes out of the hole great, runs strong all the way to 5100 rpm. didnt have gps today but seemed at least as fast as the other day when we had some issues with carb and spark. Motor mounted all the way down. AV plate is just below water when at WOT I think. Hard to see with all the water spraying. Motor had one of those hydro foils mounted to plate. Was there when I got boat. I think I will raise motor one hole and check again. Speed the other day 32.9 I recall. Very happy so far.

 

[Dhadley]

Re: 1996 88hp Johnson, 1987 McKee 17 ' offshore

We're not really concerned with where the plate is when you're running, different hull designs will cause that to be different. The plate should never be below the bottom when parallel. With today's props it's nor unusual for the plate to be an inch or more above.

5100 is lugging the motor. Raise the motor so the plate, when parallel, is no lower than than even with the bottom to no higher than an inch up. Then test and see how the prop reacts with that hull design.

 

[surrender]

Re: 1996 88hp Johnson, 1987 McKee 17 ' offshore

Thanks
I will raise it. I dont know what else to do. Motor runs great, did the link and sync, timing. All good. Dont want to change props, dont think I need to. Even in fairly sharp turns at decent speed prop doesn't ventilate or try to spin out so I think I can raise motor and get the rpm up to where it needs to be. What do you think i should be running WOT with average load on board?

 

[Dhadley]

Re: 1996 88hp Johnson, 1987 McKee 17 ' offshore

With an average laod your target top rpm is 5800. If you're using ethanol fuel without Gas Shock you may only get to 5600-5700.

 

[surrender]

Re: 1996 88hp Johnson, 1987 McKee 17 ' offshore

Raised the motor today. I went up two holes after seeing how far below the boat the AV plate was. I'll test it this week.

 

[surrender]

Re: 1996 88hp Johnson, 1987 McKee 17 ' offshore

Ran boat today after raising motor. Took a little longer to get out of the hole but it was adaquate if not pretty good. Tach only showed around 5150 top end and it would go up if I trimmed out the motor but boat would porpoise real bad as rpm's went up and boat got higher. Got to 5250 or so and boat would almost bounce and rpm's would surge and almost over rev. Think motor would be happy to turn up if you could hold it from bouncing. Sounds good. Checked all spark plugs after getting home all look about the same. Tannish electrode, darker at insulator but no signs of fouling. Dont think I'll do much more except bring an old electric tach/dwell meter that is supposed to be accurate and verify the teleflex tach. Maybe a set of tabs if I come across some used ones.