down on MPH

[Mbryan185]

hey every one just wanted to see if anyone could help or has had the same issue. I have a 1996 procraft 185pro with a 1996 mercury EFI that has been converted to carb (previous owner did this) when I got it it would run 56mph by GPS. I went out last week and it was down to 46mph. I changed plugs and found and fixed a fuel leak and got up to 50mph. I have been running the 10% ethonal fuel and mixing at 50:1. have not done a compression check yet. would seafoam and 100% gas help or should I be looking for another issue. thanks

 

[beetlespin]

You lose 2-3 mph in the hottest time of the year. Not usually 6 mph though.

 

[Mbryan185]

maybe that's what it is. I did forget to mention I put a new cranking battery in that is A LOT heavier than the old. so assuming the heavier batter cost me one or 2 mph and losing 2-3 cause of the heat that would leave me at 50-51.

 

[BulletTJ]

If you are like me, you have a lot more tackle in your boat than you had the first time you took it out.

 

[chillerman69]

both replies are correct. you can play with props to find one that performs better in the hotter water, maybe but periodically emptying your boat and reloading it, could save hundreds of pounds of unnecessary gear. The gray gear is what kills you, stuff you won't take out but also won't put back in, if it was laid in the floor or on a shelf. You should be running pure gas, whether it helps your speed, or not. If your motor has a computer or any other means to automatically advance the timing, you could pick up speed. You mentioned speed changes but never engine RPM, both are helpful/necessary to diagnose the potential issue. If you have a partner, make him jump on the scales before getting in the boat. Those K/K dognuts could be swelling him up. If you fish with your wife, forget the scales and don't worry about top speed, just enjoy the outing

 

[ChooChooSnakeMan]

I'd suggest getting a compression and leak down check on the engine done. 6 mph is pretty significant. More importantly would be what rpms did the engine run before compared to now. Weight can be a factor as mentioned and one area that a lot of people miss and unfortunately usually means big trouble on older hulls is the question of your hull actually taking on water. A lot of the older hulls had wood encapsulated transoms and stringers. Over time, especially if the boat sits in the water much or in the weather is that the wood in the hull will soak up water and you end up with a hull that could be hundreds of pounds heavier than when new. I hope this isn't your problem but if you rule out engine problems and you take all the stuff out of the boat and it still don't perform then it has to be weight of the hull or possibly a dinged prop. Even a minor ding can cost several mphs. Hope this helps.

 

[Gator]

You would be very wise to use only 100% gas. That ethanol can create really expensive problems.

 

[silvertalon]

Don't be afraid of ethanol fuels so long as the ethanol does not go beyond 10%, which it shouldn't anytime soon. Yes, eth free is better but since the mid 90's, motor manufacturers have designed and built motors to combat alcohol. It is important to use ethanol buster additives that will also stabilize the fuel. (marine stabil). This is especially important if the boat sits a lot between usage as the fuel can go sour fast the way it is now formulated- with chemical additives to achieve octane ratings, rather than thru refinement process- like the old days. Fuel now is formulated for quick turnover so it goes bad fast when it sits. Mercury recommends mid-level octane even tho their motors use a min of 87. More importantly, use the best oil you can afford. Synthetic blend is best. Quicksilver or pennzoil. Never run the tech 2000 from Walmart. It will stick your rings in a hurry. IMO