19' Seaway Prop Suggestions

Jimp

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Have a 19' Seaway that I recently re-powered with a early 90's Evinrude 90 2 stroke. I'm looking for prop suggestions. Max RPM is 5500. Current prop looks like a 13x19? 3 blade aluminum. Boat is basically a hull with a wood center console. I would estimate the boat weight under or close to 2000 lbs as it sits in the water. Runs well and jumps on plane easily but over revs and blows out past 3400 rpms. I've never needed to go any faster so I never dealt with it but I'm looking to move it soon so I'd like to get it sorted. Also if trimmed up more then 1/4 way the same happens. Over revving, loss of steering etc. Any suggestions? Looking for a good overall prop, don't need the last mph it has left in it.
 

Tunascapes

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Sounds like your cavitating more than anything. On a 90 etec I'm running pretty much the same prop and have no issues and turn up to 5200. Is your cavitation plate mounted above, in line, or below the bottom edge of the stern when in the down position.

Is the hub on your prop an old style pressed in rubber? You could also be getting slippage in the hub. Those pressed in rubber ones always have some degree of slip
 
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Jimp

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Sounds like your cavitating more than anything. On a 90 etec I'm running pretty much the same prop and have no issues and turn up to 5200. Is your cavitation plate mounted above, in line, or below the bottom edge of the stern when in the down position.

Is the hub on your prop an old style pressed in rubber? You could also be getting slippage in the hub. Those pressed in rubber ones always have some degree of slip


The anti cavitation plate is even with the bottom of the hull. I looked at the hub. It appears to be black rubber but I cant get a good look at it. I put it in gear and turned the prop over by hand. I could hear the engine building compression so I assume the hub isn't slipping. Where do you keep your seaway in Scituate? I'm on the south shore also.
 
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jerseysportfisher

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Cavitation plate on an out board is irrelevant with setting it up to the hull itself. The cav plate should be right at the water line when underway 3/4- full throttle.

should look like this

correctheightVSmall.jpg
 

Jimp

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I cant get to 3/4 throttle to check it out. The motor is mounted as low as it can go, so I would assume if anything I would be losing top end and lagging. I'm doing the opposite.
 

jerseysportfisher

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I cant get to 3/4 throttle to check it out. The motor is mounted as low as it can go, so I would assume if anything I would be losing top end and lagging. I'm doing the opposite.

where is the cave plate before it "blows out" while under way ?

by the way, is this a 20 inch shaft outboard by any chance ?
 

Tunascapes

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If it helps for a reference, my motor on the 19 has the cavitation plate 3/4" below the bottom of the transom and I have no issues at any speed.

Just so you know you can not get a good enough read on the hub by just turning the prop especially if it is happening in the mid 3s. If you can get your hands on another prop you should at least rule it out. Those rubber hubs were a nightmare.
 

Eastporter

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I had a similar problem (cavitation) with my new 80 hp Suzuki on my Eastporter 20'. I solved the problem two ways: lowered the motor one hole, and switched to a 14x17 prop. Try a larger aluminum prop for approx. $100 and it might fix your cavitation issues. Good luck
 

Jimp

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where is the cave plate before it "blows out" while under way ?

by the way, is this a 20 inch shaft outboard by any chance ?


Not sure where the plate is. I'll have to bring someone with me this week and check it out. The motor is a 20" Shaft.
 

Jimp

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If the boat is made for a 25 inch shaft, that would be a problem, see if Tuna's is a 25' shaft.


It measured out as a 20" shaft. It has a deep cut transom. The prop is dinged up on all the edges in the same spot. Would the dings in the prop cause it drop off drastically at a certain rpm.
 

jerseysportfisher

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It measured out as a 20" shaft. It has a deep cut transom. The prop is dinged up on all the edges in the same spot. Would the dings in the prop cause it drop off drastically at a certain rpm.


No, it will cause more vibration and loss off the top end, not as bad as what your describing. can you post a close up picture of your transom with the outboard ?
 

jerseysportfisher

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Based on you pics the prop has plenty of water. I am in agreement with tuna, that its most likely your hub causing you the greef. I would get a good stainless prop, never was a fan of aluminum.
 

Eastporter

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Aluminum is soft and will sacrifice itself before destroying your lower leg if you hit anything (unlike stainless).
 

Eastporter

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Don't bet on that, have seen plenty lowers grenade when an aluminum prop hit debris


They say experience is the best teacher. I know from personal experience, but of course it depends what you hit and how hard.
 

jerseysportfisher

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They say experience is the best teacher. I know from personal experience, but of course it depends what you hit and how hard.

I know what your saying, I have seen both ways, just sheer a blade and also destroy a gear case. I feel if its going to blow from hitting something, might as well enjoy the performance of a stainless until then.
 
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