Advice on second time out with boat!!

[kozman01]

After reviewing many posts, I applied this boards advice to my 1976 16'Silverline w/ 1969 Merc 800 motor and now my boat runs GREAT. I used the Mercury Engine Tune on the engine, replaced the fuel line from the tank, filter and coupler on the engine and took it out a second time and it never stalled at the high rpm's like it did the last time and it was never hard to restart like last time. I have a new question now.<br /><br />The boat has I believe a 14 or 15 pitch aluminum prop. My gps and speedo read 29 mph at 5000 rpm. I think I should be able to get a little more speed out of the boat. Any recommendations? The previous owner said the prop was set up for skiiing/tubing. Thanks for any help on this. Also, if I'm going to replace the prop. are there any seals that I should replace as well? I have a little water in the lower unit and have replaced the seals on the drain/fill screws. THanks again.

 

[kozman01]

Re: Advice on second time out with boat!!

C'mon guys, at least some help on the seals involved with the prop. Should I buy new thrust washers when I put a new prop on? Thanks again. iboats recommended I go with a 17 pitch prop. Sound ok?

 

[crazy charlie]

Re: Advice on second time out with boat!!

Water in the gear lube means you have a vacuum leak.The prop shaft seal is a good place to start looking.A vacuum and pressure check would help pinpoint the leak.If the prev owner told you it is propped for tubing then you have a working prop on it.For speed, you need a different prop.Smaller.It will take longer to plane off and will not do as well with a full load of people,but with one or two people it will go much faster after you get going. charlie

 

[Solittle]

Re: Advice on second time out with boat!!

Couple of things - I wouldn't mess with the gearcase just yet. Replacing the seals for the drain & fill plugs may have solved your problem. Check it again after running for an hour or so and if it is milky then you need to follow CC's advice & do the pressure & vacume check.<br /><br />On the prop - you need to find out what the WOT rpm is with the "usual" load that you plan to carry. 5000 rpm seems low to me but I don't have the spec. I would guess that you should be at 5500 rpm & hope that others will chime in.<br /><br />To adjust the rpm you need to take your prop to a prop shop and tell your story. They will size the one you have and either repitch yours or recommend what they think you need. The advantage in doing it that way is the prop shop should stand behind their recommendation and work with you till you get it right.

 

[kozman01]

Re: Advice on second time out with boat!!

Thanks. I did check after replacing the gaskets and I still had some water. The recommended upper range for this engine in the manual is 4800-5300 rpm. I'm only getting around 28 or so mph with the 15 pitch prop. I will forgive a little of that holeshot for some more top end. I'm just worried something bad is going to happen if I don't fix this leak. I change the oil out everytime before I go into the water. Are all those seals in the lower unit difficult to replace. Might make for a good winter project.

 

[DJ]

Re: Advice on second time out with boat!!

Kazman,<br /><br />Overpropping (less rpm) your engine is just as harmful and underpropping (more rpm).<br /><br />It looks to me like you are right where you need to be.

 

[beckerdg]

Re: Advice on second time out with boat!!

If you can't get more that 5000 rpm out of the engine/prop combination you have now a higher pitch will result in poorer performance and likely less speed. If you can turn 5300 or a bit higher you might be able to go up a couple inches in pitch. There are always exceptions like if you happen to have a large 4 blade prop, then you might be able to go to a smaller, higher pitch, 3 blade prop and get more speed.

 

[kozman01]

Re: Advice on second time out with boat!!

Thank you for the input. I think you are correct and at least for this year, I'm going to stay with the prop I have. I'm still concerned about those seals behind the prop. Is this a job a newbie with some mechanical skill can do. I'm only going to have the boat out two-three times max this year, so I may just change the oil each time and redue the seals this winter. Does this sound like a game plan?

 

[Solittle]

Re: Advice on second time out with boat!!

Sounds like a good plan to change the oil every time you go out. Oil is relatively cheap. If you decide to go for the seals yourself do the vacume/pressure test and go no farther without a factory shop manual. You can do it yourself but some motors are quite complex in the gearcase and have close tolerances.

 

[kozman01]

Re: Advice on second time out with boat!!

Thanks for all the input. It is greatly appreciated! I tlook like we might have one more nice Saturday here in dreary central OH. Man I can't wait to retire. 6 months in Vermont, 6 months in Florida.