Why have i lost 5 to 6 mph ?

[quebec#1]

I Could see a slow loss of 1 or 2 mph maybe 3 over the years but a loss of close to 6mph since last september ! My boat is 24 years old but still in very good shape my motor is a 1986 johnson 110 with good compression and my prop seems to be in good shape as well.The boat always did a solid 52mph and maybe about 53 to 54 with a clean hull. Im now down to 47 mph and the boat and motor seem to be running the same as previous years , good idle, good take off, no hesitation yet ive lost over 5mph in about a month of ridding with no noticible engine problems in performance only in top speed .

 

[Hooty]

Re: Why have i lost 5 to 6 mph ?

Do you have a tach? If you do, has the engine speed dropped off? <br />If you don't have a tach, you might think about investing in one. One can be had, for your engine, for $30-40 from TinyTach. They're almost a must for outboards for proping to troubleshooting.<br />Here's TinyTach's website and fone nr. Give 'em a call and tell them what engine you have and they'll fix ya up with a tach.<br /><br /> http://www.tinytach.com/tinytach.html <br /><br />c/6<br />Hooty

 

[Solittle]

Re: Why have i lost 5 to 6 mph ?

How are you measuring the speed?

 

[quebec#1]

Re: Why have i lost 5 to 6 mph ?

The hull has been cleaned and ive used up about 30 gallons of new gas, octane gas is the same for the last 14 years, did a decarb at the start of the season , weight is the same incl me, my motor seems not as high when tilted up from the power trim when full out, my tach never seems to work very well, it bounces to 5500 rpm to 7000 and at times gets stuck,ive stayed beside my friends seadoo and he used to be two boat lenths behind me now its reversed. <br />Perhaps peering into the carbs and a good cleaning would make a difference but would a partially blocked jet still allow the engine to run well in all conditions except top speed ?

 

[BillP]

Re: Why have i lost 5 to 6 mph ?

How is the speed measured? GPS or tube? The angle of the tube can make a big difference in reporting.

 

[mbb]

Re: Why have i lost 5 to 6 mph ?

weak spark to a cyl could cause that. a coil or plug wire going bad . more complicated things like loss of primary compression on a cyl (leaking reed valve or crancase seal) that reduces fuel/air mix to 1 cyl. a regular comp. test wont show that.

 

[quebec#1]

Re: Why have i lost 5 to 6 mph ?

Thanks for the info guys, you gave me a good insite as to what to look for.<br />Thanks Gary.....

 

[cobra 3.0]

Re: Why have i lost 5 to 6 mph ?

If you are not using a GPS as BillP mentionned, you don't know how fast you are really going.

 

[Bob in Calif.]

Re: Why have i lost 5 to 6 mph ?

GaryB.........<br /><br />I have a 1978 Campion Cuddy Cabin, (Canadian built), that I bought with an 85hp Johnson. the boat would top out at apx. 29 to 30 mph. I wanted more speed out and found a sweet deal on a low hour 150hp.<br /><br />While doing the engine change over, I found the transom was rotten and saturated with water. I pulled the flooring up to access the transom to replace and found all the foam under the floor was totally saturated with water. The boat did not leak one drop, but the water damage was due to the build up of rain water and water from washing it, etc, over the years, by the preivous owner.<br /><br />After replalcing the transom and refoaming the hull, I sealed the floor and took it for a test ride. The boat sat up at least 2 inches higher in the water and my speed increased by apx. FOUR MPH. and with greater handling, still uning the same 85hp motor.<br /><br />The soaked transom wood and foam had added several hundred pounds to my boat, causing the decrease in speed and handling. <br />It might be worth your while to check the foam and see if it holding water. This might be be the cause of your speed loss.<br /><br />The acutal cause of the water saturation, was the lack of resin saturation on the glass cloth, especially at the base of the trasom, near the drain plug area. This was a factory defect from the day it was built.<br /><br />...Bob in Calif...

 

[quebec#1]

Re: Why have i lost 5 to 6 mph ?

The thought has cross my mind,that the transom might be a little weak, my boat is a 1980 glastron gt 150 and they do have transom problems. The boat did sit indoors for the winter, for 7 months in a semie heated garage, so i figured that the boat should be dry. Its stored without the cover so the moister can get out. So with the clean hull at the start of season it did only 49mph vs the 54mph of last year, even with the hull dirty last summer it did a strong 52mph until late last summer when it dropped and now its all the way down to 47 mph.<br />Its not a faulty speedoo because ive done some runs with my friends boat next to me and he is two boat lenths + ahead of me it used to be the opposite.

 

[Bob in Calif.]

Re: Why have i lost 5 to 6 mph ?

Hi again Gary....<br /><br />The boat I bought from "Pa Kettle" was very well taken care of by him. Always covered, etc. But I still encountered the transom/foam problem. <br /><br />Water in the transom wood and water in the non-closed cell foam is like a "roach motel." The water get's in, but doesn't get out."<br /><br />It would be worth your while to investigate the condition of your transom wood and your foam.<br /><br />Good luck... ...Bob in Calif...