I have a 2008 model Suzuki 4 stroke 90hp outboard fitted to a 5.25 center console alum. boat. The stainless steel prop fitted by the dealer is a 3 blade, 14 x 18 which although has good low speed grunt, it lacks top speed, compared to my previous 90 hp 2 stroke. The motor struggles to go over 30 mph, at 5000 RPM, in flat conditions with 2 people & fishing gear on board. I don't like running at these near top revs and was considering changing the prop to increase top end speed, without sacrificing low speed grunt taking off. Can you suggest a prop size to rectift this problemthanks,Neville Richardson
Make (of engine): SuzukiModel (of engine): DF90Year: 2008Horsepower: 90
nothing, only engine trimming
The propeller is not only responsible for propulsion, it is also responsible for being a governor for the engine. All boat engines are rated at wide open throttle RPM. Your Suzuki DF90 is rated 4500 - 5500 RPM. What this means, with the boat loaded down the RPM cannot be below 4500 RPM at wide open throttle. this is called lugging. When the boat is empty and with one person the RPM cannot go over 5500 RPM. This is called REDLINE.Before I suggest a prop. Do you understand everthing I have said?
Yes I understand what you are saying, however I have no problem getting to peak revs (5500), just not getting enough speed at these revs. I would prefer to back of the revs to around 4800, and speed around 35+mph. I don't like running the motor at peak or near peak revs.
Propeller rules that everyone should know.Increase pitch decrease RPM. Decrease Pitch increase RPMCurrently you have a 14" diameter 18" pitch propeller. We need to increase pitch to decrease RPM. I have looked online and the only propellers I have found are 14.25"DX19P and a 14"DX21P. If I had this boat in the service department I would order and try both of these propellers. Why? for clearance(14.25 diameter is bigger and could strike tab). the 14"D21P I would test run to see if RPMs dropped to low. Its all about fine tuning. A High percentage of dealerships let you test Propellers before purchase. Each has a different purchase policy that they want you to follow.If you don't want to fine tune the propellers then my answer is get the 14.25"Dx19P. Just be aware you may need to change tab.If you have any question about my answer please fill free to ask.Thanks XXXXX XXXXX
Over 18 years experience in the water sports repair industry.
14.25" may to big a diameter to fit under the outboard fin, the distance from the center of the propellar spline to the underside of the fin is only 7.3/8 inches. 14.25" would only leave 1/4 inch clearance , is this enough?? I thought perhaps i must either go to a 4 blade prop (which I know nothing about) or increase the pitch. what do you think??
I love four blade props, but with a four blade I would start over. At the shop I would put the boat in the water with 3 props in the boat, and fine tune it that way.So my suggestion if going to a 4 blade is find a dealer that has a prop test policy. Stainless steel 4 blades are way to expensive for me (in good concience) to suggest were to start.Plus, I just got word from my supervisor that the RPM Range on your year model, may have been updated to 5300 to 6300 RPM. 14.25"Dx19P I suggested has to stay above 5300 RPM in a fully loaded boat.