Thanks to this forum and the incredibly smart people on here I was finally able to take my boat for its first test run! So I have some new questions.. The boat is 100HP, I know that's not at the prop, but I was really disappointed at the performance of the motor. It starts and idols fine but when I take off its really slow. I had 4 passengers maybe 650# and we could barely get a max speed of 11 mph (motor is on 1967', 19' hydro swift fiberglass boat). Before putting it on the water I pulled and drained the gas tank, put 16 gallons new 91 octane, I used the Johnson synthetic 2 stroke XD50 oil and 32 oz. sea foam (2 oz per gallon was recommended for 2 stroke motors). The boat has sat for over a year I figured that was a good clean start. We drove for about a good half hour with throttle completely opened still not much difference. At one point I stopped the boat and it actually died. I checked the plugs and they were getting a little wet. I dried and adjusted fuel mixture a little leaner. My speed dropped a another mile slower. We decided to bring the boat in. While I was waiting for the girls to get the truck my friend and I decided to take for a quick cruise around. This time it got max speed of 27 mph! almost 3 times faster than before, but still slow getting to that point. Our girlfriends weigh maybe 120 # so I don't think it was a weight issue. I checked compression it was hitting over 100 psi on all 4 and were in 10% range of each other. but its an old tester. I bought a new one and plan to retest.
When the motor was new what kinda of compression did it have? What is an acceptable range for this old motor? Is this motor worth redoing the piston rings with the psi it has now? Did it ever have good take off? The older motors could run OK with lower compression and leaded fuel. Do I need to do any major upgrades to the block, pistons or piston rings to get the compression needed to run the unleaded fuels. Am I completely off on the unleaded fuel thing?? I'm new to boat motors, but the mechanical end of building this motor shouldn't be hard so I don't mind dumping a few hundred dollars into it if I can get the performance I'm looking for out of it. This is a boat restore project me and my girlfriend are working on we dig the look of the old vintage motor on this boat so we would rather not replace it if we don't have to. but I dig speed also and ultimately that's what I'm hoping to gain from this work. I know its not a speed boat I'm not expecting that. but feel I definitely should be getting more power from this motor. Does any one have any input? Has anyone drove one of these motors when it was running great? sorry for the long post, thank you everyone!
When the motor was new what kinda of compression did it have? What is an acceptable range for this old motor? Is this motor worth redoing the piston rings with the psi it has now? Did it ever have good take off? The older motors could run OK with lower compression and leaded fuel. Do I need to do any major upgrades to the block, pistons or piston rings to get the compression needed to run the unleaded fuels. Am I completely off on the unleaded fuel thing?? I'm new to boat motors, but the mechanical end of building this motor shouldn't be hard so I don't mind dumping a few hundred dollars into it if I can get the performance I'm looking for out of it. This is a boat restore project me and my girlfriend are working on we dig the look of the old vintage motor on this boat so we would rather not replace it if we don't have to. but I dig speed also and ultimately that's what I'm hoping to gain from this work. I know its not a speed boat I'm not expecting that. but feel I definitely should be getting more power from this motor. Does any one have any input? Has anyone drove one of these motors when it was running great? sorry for the long post, thank you everyone!
