Thanks so much for your input!
I did look at my almost new prop but it is fine. After taking the prop shaft apart and letting a good marine mechanic look at it, he said the forward and reverse gears were about the worst he had seen and that was my problem. I tried adjusting linkages but when I had immediate problems with not holding gear case oil, I gave up.on the old motor. Too much money for the parts to end up with still a really old engine.
I did not strike anything. It was just wear according to the mechanic. I bought the motor with the boat and the previous owner had found the motor locally after redoing the boat, so no history is known.
Thank you for all that!
I found that the lower unit prop gears are peened over from wear. A trusted local marine mechanic tells me they are in very bad shape. Also, it has been leaking water into the lower unit so the seals are shot.
I do not know why that is its top speed (GPS) but the friend from whom I bought it was getting that before I bought it too. It is a short shaft and I re-propped it when I bought it with a 10.3"x13. It is a 15" shaft.
So when the best price for a used lower unit was over $300 and could not get the fellow on ebay to write me back who rebuilt them, I have now bought a Tohatsu 25 for a very good price for a new engine. I have the old Merc for sale locally as I could not see putting $700 or more into it and still having a 23 year old motor.
We shall see! I get it next week.
As a counter-point, have you checked to ensure that your propeller clutch (rubber hub) is not slipping? The 1980-2006 Merc 25 typically do not have lower unit issues without impact or water intrusion damage, barring maladjustment of the remote control cables. As well advised, if the Merc 25 is not a long shaft model, the "hydro-foil" is removed (acceleration holes can be added to the propeller tube to decrease time to "plane"), the outboard mounting height is correctly set, and the correct propeller pitch is in use, note that the Suzuki will offer no performance increase, as the 1980 & newer Merc 25 models are propeller shaft horsepower rated, and have 24.4 cubic inch piston displacement. If an impact has caused damage, your home owner's insurance might have "standard policy" coverage of your boat/motor/trailer, and cover striking an underwater object. Auto insurance (of the tow vehicle) could cover damage when towing.
I have a Suzuki DF25ARS on my 1955DR. I get a solid 29MPH with my wife and I onboard. If you're only getting 20 MPH, then I'd guess you have a long-shaft motor or it's poorly propped. That whale tail certainly isn't helping your speed any. If that whale tail is on a long-shaft motor, then you're adding a lot of drag to the boat.
I really like the Suzuki on my DR. Yes, it IS blasphemy, but I don't care. It's a joy to ride around in, and pops out to full speed in 2-3 seconds. IMHO it would be a great replacement for your Merc.
FYI, I put the short-shaft Suzuki on my DR. About a year later I raised it about 1 1/4 inches on the transom to reduce the drag - which bought me about 1 MPH on the top end. I also replaced the factory 11-pitch aluminum prop with a higher-pitch stainless prop - which I kind of regret. The stainless prop is louder for some reason, especially at idle, and doesn't run as smooth as the original prop. And of course it was expensive. The prop also got me about 1 MPH top speed, but I'm not sure it's worth it. Search my posts for more details on my experience with the motor.
I'm in North Alabama and usually have my boat at Arrowhead, if you want to go for a ride!
BTW, if you're thinking about the Suzuki, then I believe your max HP will be 25, because I don't think Suzuki offers the 30 HP motor in a short shaft, and IMHO you really should be putting a short shaft motor on these boats. The Zuki 25 & 30 are basically the same mechanical platform. I hacked my motor to increase the HP from 25 to 30 (I think), and it didn't buy me any measurable increase in performance. It "feels" more confident to me, but it didn't get my integer-reading GPS up to the next MPH.
I am sorry- I posted this on the General Information forum, and could not figure out how to move it, so here it is again...
I have two questions:
1. Would it be blasphemy to put a new Honda or Suzuki on my 1955 Deluxe Runabout?
I have a 1984 Mercury 25 on it now that has just lost its lower unit. I don't really want to put that much money into an old motor.
2. If I did put a new Honda or Suzuki on this boat, what would the max horsepower be? According to the catalog here, it was rated for a 40 HP (at the engine, not the prop). The Merc 25 gets it to 18-19 knots or so with two people in the front seat. It has all that aluminium reinforcing in the stern.
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