You guys are making me very depressed. I just ordered the 2008 6HP Nissan OB engine for my Morgan 25 which weighs 5,000 pounds. The Nissan dealer says the only options for the prop is 7, 8 or 9 inch and the engine comes with the 8 inch prop.
Some questions for Audeojude: What year engine did you test? A 6" pitch prop is not offered on the new engines. I'm currently using a 3.5 HP Nissan 2 cycle outboard and it pushes the boat at 5 knots with no winds blowing. Where can I buy a smaller pitch prop? Are you sure your instrunents are calibrated properly? I might still be able to exchange the OB for the 8HP model but don't want the extra weight and I also wanted the extra long shaft.
Please respond ASAP
My tohatsu 6hp engine is a 2007 engine. The nissan 6hp i tested is a 2005 model. Unless they changed the shaft that the prop goes on you should be able to buy any prop sold for the nissan/tohatsu/mercury engines in the 4/5/6 hp range.
Someone on this discussion mentioned a mercury power prop that fits these engines. I have not tried it but it would be what I went to next if I do anything. The tohatsu 6 pitch prop is 52 dollars if i remember right ordered from tohatsu.
For what its worth my boat is much lighter than yours and very sensitive to weight on the transom I bet. If I were you I would go to the 9.8 which has the ultralong shaft and is two cylinder engine. I am told it runs smooth as silk and very quietly.. I do not have personal experience of this though. I dont think you are going to see a huge difference on a 5000 lb boat of the added 30 lbs of weight between the 6hp and 9.8hp engines. I don't believe the 8hp comes in the ultralong 25" shaft model
I would think that you would move boat speed up to 6.5 knots or thereabouts if you are getting 5 with a 3.5 motor. However take this with a grain of salt as I do not have hands on experience with the 8 or 9.8 engines.
My knot meter and gps both are in agreement as to what speed the boat is going. the currents where I am are very consistent and my gps speed always agrees with the knot meter + or - the current. On the ocean with no current they will both agree to .05 of a knot.
given the 1 to 1.5 hour trip each way to go sailing I have a lot of accumulated data with the old engine and the new engine on the water with it running. I pulled the new engine when I decided to try and return it just before my 2 months grace period for disputing a credit card charge was up. In the two months working on this engine with the manufacture and in the normal course of operations where I am I put in excess of 40 hours on it. I was disappointed in it.
Sadly i had a opportunity for a 9 or 8? hp honda 25 inch shaft outboard 6 months prior to purchasing this engine for the same price. It was used only 20 hours on it. I bitterly regret not having the money to purchase it then.