17 foot express w/90
 

I have a 17 foot express with a 2 stroke 90 yamaha. Never has given me any problems. the compression on the engine is on the lower end of normal but still normal. I installed a 6 inch manual jack plate a year ago and have been using it cranked all the way up. I can get pretty shallow in marsh. I top out between 35 to 39 mph usually at 37. The cativation plate is probably 6 inches above the bottom of the boat. I know this is pretty high and i like it for shallow water but I would like to have a higher top speed if possible when making longer hikes. Does anyone think that I might get more top end speed if i drop the cativation plate to about 1 inch above the bottom of the boat? any advice would be appreciated. Where it is now I cannot really move the trim much because the boat will start to buck pretty quickly even on calm water. thanks.

Sounds like your too high for sure. Try dropping the motor 1" at a time and run it till mph starts dropping again. Also you may want to check your water pressure running it that high. I've got a 17' borel with 90 mercury with 6" jack plate and can run 50 in good water. So you should be able to do better than what your doing.

thanks. before I put the jack plate on it would do about the same speed. It should do better but didn't. i met a guy at a marina who had the exact set up as me and told me his boat would top out under 40 then put on a 6 inch jack plate and now would hit 50. I bought one and didnt get the top end speed but like the peace of mind of having the engine up so high because of the marsh im usually in. I'm going tomorrow hopefully and going to make about a 10 mile ride to my first spot so I wanted to make some adjustments. I almost always cruise at 4000 rpm and my speed fluctuates from 28 to 31. Should I be able to tell a difference if Im not maxed out or do I need to oped it up to see the top end difference. Thanks and I appreciate the response.

I had a H-51 express with a 90 yam. No plate it would run 46 with 2. Your mota is too high. Do you have a water pressure guage?

You can't just put a jack plate on, set it all the way up and go with it like that. You will go slower, blow out, beat your self to death and loose your water pressure. It needs to be adjusted to your boat and prop setup. It's hard to tell you where to set it but you need to drop the motor and start inching it up till speed falls off and it rides good with trim

thanks guys. I really have just done everything myself when it comes to boating and fishing. my cousin and i just wanted to start fishing so we did and really never fished before hand so we have definitely made some mistakes but nothing major. no i do not have a water pressure gauge. I have always just checked to see if the motor was peeing and it always has but never anything more scientific than that. going out tomorrow and have the wrench handy and will test out a bunch of heights. I set it down low where the cativation plate is about 1 inch above the bottom of the boat and I will go up from there. I will let you know how it goes. thank yall for all the help.

sorry guys but couldnt get out on the water this weekend the wife had things come up. but as soon as i do I will let you know. thank you for all the help